| 1. |
- Andoralov, Viktor, et al.
(författare)
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Biofuel cell based on microscale nanostructured electrodes with inductive coupling to rat brain neurons
- 2013
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm−2 in vitro and 2 μW cm−2 in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons.
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| 2. |
- Aroonsang, Watcharapong, et al.
(författare)
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Influence of substratum hydrophobicity on salivary pellicles : organization or composition?
- 2014
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Ingår i: Biofouling (Print). - : Taylor & Francis. - 0892-7014 .- 1029-2454. ; 30:9, s. 1123-1132
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Tidskriftsartikel (refereegranskat)abstract
- Different physico-chemical properties (eg adsorption kinetics, thickness, viscoelasticity, and mechanical stability) of adsorbed salivary pellicles depend on different factors, including the properties (eg charge, roughness, wettability, and surface chemistry) of the substratum. Whether these differences in the physico-chemical properties are a result of differences in the composition or in the organization of the pellicles is not known. In this work, the influence of substratum wettability on the composition of the pellicle was studied. For this purpose, pellicles eluted from substrata of different but well-characterized wettabilities were examined by means of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that substratum hydrophobicity did not have a major impact on pellicle composition. In all substrata, the major pellicle components were found to be cystatins, amylases and large glycoproteins, presumably mucins. In turn, interpretation of previously reported data based on the present results suggests that variations in substratum wettability mostly affect the organization of the pellicle components.
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| 3. |
- Bahmanzadeh, Safiyeh, et al.
(författare)
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Proteolytic degradation of gelatin-tannic acid multilayers
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 526, s. 244-252
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis Gelatin is one of the most popular constituents of biodegradable/edible films. Because of its poor mechanical properties, it typically needs to be cross-linked. In this regard, the use of tannic acid has attracted significant interest. Whereas the biodegradability of gelatin is well established, little is known on how different crosslinking methods affect biodegradability. In most cases, the ionic strength at which protein films are grown has a drastic effect on their structure. Thus, it is expected that by controlling the ionic strength during the growth of cross-linked gelatin films it should be possible to tune the access to relevant cleavage sites by proteases and, therefore, their biodegradability. Experiments Gelatin-tannic acid were grown at different ionic strengths by means of the layer-by-layer self-assembly method. The growth of these multilayers and their response to the presence of different proteases were monitored by means of Electrochemical Impedance Spectroscopy and Quartz Crystal Microbalance with Dissipation. Findings Gelatin-tannic acid multilayers grown at low ionic strength exhibited a swollen structure that allowed easy access to their cleavage sites by proteases. Multilayers formed at physiological ionic strength exhibited a compacter structure, which limited their proteolytic degradation.
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| 4. |
- Barrantes, Alejandro, et al.
(författare)
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Influence of pH on the build-up of poly-L-lysine/heparin multilayers
- 2012
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 388:1, s. 191-200
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Tidskriftsartikel (refereegranskat)abstract
- The effect of pH on the build-up-of polyelectrolyte multilayers, PEMs, composed by poly-L-lysine and heparin onto two different substrates, silica and gold, has been studied by means of ellispmetry and quartz crystal microbalance with dissipation, QCM-D. Ellipsometry results indicate that the dry mass grows exponentially with the number of layers, and that this amount is larger as the pH values are raised. From QCM-D data the viscoelastic properties of the multilayered structure have been obtained. These data reflect that PEMs become more viscoelastic as the pH values are increased for silica substrates, while for gold the highest viscoelastic behavior is obtained at neutral pH and the elastic behavior becomes dominant as the pH is further increased or decreased. By combining these two surface techniques it has been also possible to determine the solvent content in the multilayers and reach a deeper understanding of the internal structure.
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| 5. |
- Boyd, Hannah, 1994-, et al.
(författare)
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A comparison between the structures of reconstituted salivary pellicles and oral mucin (MUC5B) films.
- 2021
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 584, s. 660-668
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Tidskriftsartikel (refereegranskat)abstract
- HYPOTHESIS: Salivary pellicles i.e., thin films formed upon selective adsorption of saliva, protect oral surfaces against chemical and mechanical insults. Pellicles are also excellent aqueous lubricants. It is generally accepted that reconstituted pellicles have a two-layer structure, where the outer layer is mainly composed of MUC5B mucins. We hypothesized that by comparing the effect of ionic strength on reconstituted pellicles and MUC5B films we could gain further insight into the pellicle structure.EXPERIMENTS: Salivary pellicles and MUC5B films reconstituted on solid surfaces were investigated at different ionic strengths by Force Spectroscopy, Quartz Crystal Microbalance with Dissipation, Null Ellipsometry and Neutron Reflectometry.FINDINGS: Our results support the two-layer structure for reconstituted salivary pellicles. The outer layer swelled when ionic strength decreased, indicating a weak polyelectrolyte behavior. While initially the MUC5B films exhibited a similar tendency, this was followed by a drastic collapse indicating an interaction between exposed hydrophobic domains. This suggests that mucins in the pellicle outer layer form complexes with other salivary components that prevent this interaction. Lowering ionic strength below physiological values also led to a partial removal of the pellicle inner layer. Overall, our results highlight the importance that the interactions of mucins with other pellicle components play on their structure.
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| 6. |
- Boyd, Hannah, 1994-, et al.
(författare)
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Effect of nonionic and amphoteric surfactants on salivary pellicles reconstituted in vitro
- 2021
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Surfactants are important components of oral care products. Sodium dodecyl sulfate (SDS) is the most common because of its foaming properties, taste and low cost. However, the use of ionic surfactants, especially SDS, is related to several oral mucosa conditions. Thus, there is a high interest in using non-ionic and amphoteric surfactants as they are less irritant. To better understand the performance of these surfactants in oral care products, we investigated their interaction with salivary pellicles i.e., the proteinaceous films that cover surfaces exposed to saliva. Specifically, we focused on pentaethylene glycol monododecyl ether (C12E5) and cocamidopropyl betaine (CAPB) as model nonionic and amphoteric surfactants respectively, and investigated their interaction with reconstituted salivary pellicles with various surface techniques: Quartz Crystal Microbalance with Dissipation, Ellipsometry, Force Spectroscopy and Neutron Reflectometry. Both C12E5 and CAPB were gentler on pellicles than SDS, removing a lower amount. However, their interaction with pellicles differed. Our work indicates that CAPB would mainly interact with the mucin components of pellicles, leading to collapse and dehydration. In contrast, exposure to C12E5 had a minimal effect on the pellicles, mainly resulting in the replacement/solubilisation of some of the components anchoring pellicles to their substrate.
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| 7. |
- Boyd, Hannah, 1994-
(författare)
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On the structure and mechanical properties of in vitro salivary pellicles
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Salivary pellicles display exceptional hydration and lubrication performance. At present, there are still gaps in the understanding of how this is achieved. The aim of this thesis was therefore to increase our knowledge on the mechanisms underlying these properties and deepen the understanding of how they are related to the composition and structure of pellicles, with a focus on those formed under in vitro conditions. This has applications ranging from the development of artificial saliva and lubricating coatings for biomedical applications to methodological approaches for initial testing of oral healthcare products. For this, we also focused on developing suitable methodological approaches for these studies, centering on atomic force microscopy, quartz crystal microbalance with dissipation monitoring, ellipsometry and neutron reflectometry techniques, to investigate in vitro and model salivary pellicles.First, we confirmed a two-layer structure for in vitro salivary pellicles and showed that the outer layer is mainly composed by the oral mucin MUC5B, but that it also contains other salivary components that enhance swelling and hydration. In the presence of bulk saliva, the outer layer also contains a reversibly and loosely bound fraction. This fraction increases the adhesiveness of the pellicle but unexpectedly has no significant effect on its lubrication performance. We also investigated the effect of mechanical confinement on model salivary pellicles by means of Neutron Reflectometry, revealing that at a pressure of 1 bar they are already completely compressed and dehydrated. Finally, with the aim to advance towards better oral healthcare products, we investigated the effect of nonionic and amphoteric surfactants on salivary pellicles, showing that they have a gentler effect on pellicle structure than the commonly employed anionic surfactants.
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| 8. |
- Clifton, Luke A, et al.
(författare)
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Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques.
- 2020
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier. - 0001-8686 .- 1873-3727. ; 277
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Tidskriftsartikel (refereegranskat)abstract
- Cellular membranes are complex structures and simplified analogues in the form of model membranes or biomembranes are used as platforms to understand fundamental properties of the membrane itself as well as interactions with various biomolecules such as drugs, peptides and proteins. Model membranes at the air-liquid and solid-liquid interfaces can be studied using a range of complementary surface-sensitive techniques to give a detailed picture of both the structure and physicochemical properties of the membrane and its resulting interactions. In this review, we will present the main planar model membranes used in the field to date with a focus on monolayers at the air-liquid interface, supported lipid bilayers at the solid-liquid interface and advanced membrane models such as tethered and floating membranes. We will then briefly present the principles as well as the main type of information on molecular interactions at model membranes accessible using a Langmuir trough, quartz crystal microbalance with dissipation monitoring, ellipsometry, atomic force microscopy, Brewster angle microscopy, Infrared spectroscopy, and neutron and X-ray reflectometry. A consistent example for following biomolecular interactions at model membranes is used across many of the techniques in terms of the well-studied antimicrobial peptide Melittin. The overall objective is to establish an understanding of the information accessible from each technique, their respective advantages and limitations, and their complementarity.
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| 9. |
- Cukkemane, Nivedita, et al.
(författare)
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Anti-adherence and bactericidal activity of sphingolipids against Streptococcus mutans
- 2015
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Ingår i: European Journal of Oral Sciences. - : John Wiley & Sons. - 0909-8836 .- 1600-0722. ; 123:4, s. 221-227
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the anti-biofilm activity of sphingosine, phytosphingosine (PHS), and sphinganine for: (i) anti-adherence activity on hydroxyapatite (HA) surfaces; and (ii) bactericidal activity on different Streptococcus mutans phenotypes (i.e. planktonic cells and cells from a disrupted biofilm). For this, HA discs treated with sphingolipids were incubated with S. mutans and the number of adherent cells was evaluated by both culture and confocal microscopy. Sphinganine strongly inhibited bacterial adherence by 1000-fold compared with an untreated surface. Phytosphingosine and sphingosine inhibited bacterial adherence by eight- and five-fold, respectively, compared with an untreated surface. On saliva-coated HA, sphinganine and PHS inhibited bacterial adherence by 10-fold. Bactericidal activity of sphingolipids was evaluated by culture. For biofilms, the strongest bactericidal activity was exhibited by sphingosine compared with PHS and sphinganine. At a concentration of 12.5 μg ml−1, PHS and sphingosine were profoundly effective against planktonic and disrupted biofilms; and sphinganine reduced the number of cells in planktonic form by 100-fold and those derived from a disrupted biofilm by 1000-fold. Atomic force microscopy studies suggested that mechanical stability does not appear to be a factor relevant for anti-fouling activity. The results suggest that sphingolipids may be used to control oral biofilms, especially those loaded with S. mutans.
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| 10. |
- Delvar, Alice, et al.
(författare)
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Interaction of polyelectrolytes with salivary pellicles on hydroxyapatite surfaces under erosive acidic conditions
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 38:7, s. 21610-21618
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Tidskriftsartikel (refereegranskat)abstract
- The modification of acidic beverage formulations with food-approved, nonhazardous substances with antierosive properties has been identified as a key strategy for counteracting the prevalence of dental erosion, i.e., the acid-induced dissolution of hydroxyapatite (HA, the main mineral component of tooth surfaces). While many of such substances have been reported, very little is known on how they interact with teeth and inhibit their acid-induced dissolution. With the aim of filling this gap in knowledge, we have studied under acidic conditions the interaction between two polyelectrolytes of differing ionic character, carboxymethyl cellulose (CMC) and chitosan, and saliva-coated hydroxyapatite, i.e., a model for the outer surface of teeth. These studies were performed by means of ellipsometry, quartz crystal microbalance with dissipation monitoring, and atomic force microscopy. We also studied, by means of pH variations, how dissolution of saliva-coated HA is affected by including these polyelectrolytes in the erosive solutions. Our results confirm that salivary films protect HA from acid-induced dissolution, but only for a limited time. If the acid is modified with CMC, this polyelectrolyte incorporates into the salivary films prolonging in time their protective function. Eventually, the CMC-modified salivary films are removed from the HA surfaces. From this moment, HA is continuously coated with CMC, but this offers only a weak protection against erosion. When the acid is modified with the cationic chitosan, the polyelectrolyte adsorbs on top of the salivary films. Chitosan-modified salivary films are also eventually replaced by bare chitosan films. In this case both coatings offer a similar protection against HA dissolution, which is nevertheless notably higher than that offered by CMC.
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| 11. |
- Falco, Cigdem Yucel, et al.
(författare)
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Design of a potentially prebiotic and responsive encapsulation material for probiotic bacteria based on chitosan and sulfated beta-glucan
- 2017
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 487, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Chitosan and sulfated oat beta-glucan are materials suitable to create a prebiotic coating for targeted delivery to gastrointestinal system, using the layer by layer technology. Experiment: Quartz crystal microbalance with dissipation (QCM-D), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) were used to assess the multilayer formation capacity and characterize the resulting coatings in terms of morphology and material properties such as structure and rigidity. The coating of colloidal materials was proven, specifically on L acidophilus bacteria as measured by changes in the bacterial suspension zeta potential. Viability of coated cells was shown using plate counting method. The coatings on solid surfaces were examined after exposure to mimics of gastrointestinal fluids and a commercially available beta-glucanase. Findings: Successful build-up of multilayers was confirmed with QCM-D and SE. Zeta potential values proved the coating of cells. There was 2 log CFU/mL decrease after coating cells with four alternating layers of chitosan and sulfated p-glucan when compared to viability of uncoated cells. The coatings were partially degraded after exposure to simulated intestinal fluid and restructured as a result of beta-glucanase treatment, mimicking enzymes present in the microflora of the human gut, but seemed to resist acidic gastric conditions. Therefore, coatings of chitosan and sulfated beta-glucan can potentially be exploited as carriers for probiotics and delicate nutraceuticals. (C) 2016 Elsevier Inc. All rights reserved.
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| 12. |
- Falk, Magnus, et al.
(författare)
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Biofuel cell as a power source for electronic contact lenses
- 2012
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 37:1, s. 38-45
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Tidskriftsartikel (refereegranskat)abstract
- Here we present unequivocal exptl. proof that microscale cofactor- and membrane-less, direct electron transfer based enzymic fuel cells do produce significant amts. of elec. energy in human lachrymal liq. (tears). 100 μm diam. gold wires, covered with 17 nm gold nanoparticles, were used to fashion three-dimensional nanostructured microelectrodes, which were biomodified with Corynascus thermophilus cellobiose dehydrogenase and Myrothecium verrucaria bilirubin oxidase as anodic and cathodic bioelements, resp. The following characteristics of miniature glucose/oxygen biodevices operating in human tears were registered: 0.57 V open-circuit voltage, about 1 μW cm-2 max. power d. at a cell voltage of 0.5 V, and more than 20 h operational half-life. Theor. calcns. regarding the max. recoverable elec. energy can be extd. from the biofuel and the biooxidant, glucose and mol. oxygen, each readily available in human lachrymal liq., fully support our belief that biofuel cells can be used as elec. power sources for so called smart contact lenses.
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| 13. |
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| 14. |
- Gonzalez-Martinez, Juan F, et al.
(författare)
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Effect of Relative Humidity on the Viscoelasticity of Thin Organic Films Studied by Contact Thermal Noise AFM
- 2019
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:18, s. 6015-6023
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Tidskriftsartikel (refereegranskat)abstract
- Material scientists are in need of experimental techniques that facilitate a quantitative mechanical characterization of mesoscale materials and, therefore, their rational design. An example is that of thin organic films, as their performance often relates to their ability to withstand use without damage. The mechanical characterization of thin films has benefited from the emergence of the atomic force microscope (AFM). In this regard, it is of relevance that most soft materials are not elastic but viscoelastic instead. While most AFM operation modes and analysis procedures are suitable for elasticity studies, the use of AFM for quantitative viscoelastic characterizations is still a challenge. This is now an emerging topic due to recent developments in contact resonance AFM. The aim of this work was to further explore the potential of this technique by investigating its sensitivity to viscoelastic changes induced by environmental parameters, specifically humidity. Here, we show that by means of this experimental approach, it was possible to quantitatively monitor the influence of humidity on the viscoelasticity of two different thin and hydrophobic polyurethane coatings representative of those typically used to protect materials from processes like weathering and wear. The technique was sensitive even to the transition between the antiplasticizing and plasticizing effects of ambient humidity. Moreover, we showed that this was possible without the need of externally exciting the AFM cantilever or the sample, i.e., just by monitoring the Brownian motion of cantilevers, which significantly facilitates the implementation of this technique in any AFM setup.
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| 15. |
- Gonzalez-Martinez, Juan Francisco, et al.
(författare)
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Humidity-induced phase transitions of surfactants embedded in latex coatings can drastically alter their water barrier and mechanical properties
- 2018
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Latex coatings are environmentally friendly i.e., they are formed from aqueous polymer dispersions, are cheap to produce and provide exceptional mechanical properties. Therefore, they are ubiquitous and can be found in a wide range of different applications such as paints and varnishes, pressure-sensitive adhesives, textiles, construction materials, paper coatings and inks. However, they also have weaknesses and their surfactant content is among them. Surfactants are often needed to stabilize polymer particles in the aqueous latex dispersions. These surfactants also form part of the coatings formed from these dispersions, and it is well-known that they can lower their performance. This work further explores this aspect and focuses on the role that embedded surfactant domains play in the response of latex coatings to humid environments. For this purpose, we made use of several experimental techniques where humidity control was implemented: quartz crystal microbalance with dissipation, atomic force microscopy and differential scanning calorimetry. By means of this multimethodological approach, we report that surfactants embedded in latex coatings can undergo humidity-induced transitions towards more hydrated and softer phases, and that this results in a drastic decrease of the mechanical and water barrier properties of the whole coatings. Subsequently, this work highlights the potential of taking into account the phase behavior of surfactants when choosing which ones to use in the synthesis of latex dispersions as this would help in predicting their performance under different environmental conditions.
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| 16. |
- Gonzalez-Martinez, Juan F, et al.
(författare)
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MUC5B mucin films under mechanical confinement : A combined neutron reflectometry and atomic force microscopy study.
- 2022
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 614, s. 120-129
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Tidskriftsartikel (refereegranskat)abstract
- HYPOTHESIS: Among other functions, mucins hydrate and protect biological interfaces from mechanical challenges. Mucins also attract interest as biocompatible coatings with excellent lubrication performance. Therefore, it is of high interest to understand the structural response of mucin films to mechanical challenges. We hypothesized that this could be done with Neutron Reflectometry using a novel sample environment where mechanical confinement is achieved by inflating a membrane against the films.EXPERIMENTS: Oral MUC5B mucin films were investigated by Force Microscopy/Spectroscopy and Neutron Reflectometry both at solid-liquid interfaces and under mechanical confinement.FINDINGS: NR indicated that MUC5B films were almost completely compressed and dehydrated when confined at 1 bar. This was supported by Force Microscopy/Spectroscopy investigations. Force Spectroscopy also indicated that MUC5B films could withstand mechanical confinement by means of steric interactions for pressures lower than ∼ 0.5 bar i.e., mucins could protect interfaces from mechanical challenges of this magnitude while keeping them hydrated. To investigate mucin films under these pressures by means of the employed sample environment for NR, further technological developments are needed. The most critical would be identifying or developing more flexible membranes that would still meet certain requirements like chemical homogeneity and very low roughness.
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| 17. |
- Gonzalez-Martinez, Juan Francisco, et al.
(författare)
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The role of cross-linking in the scratch resistance of organic coatings : An investigation using Atomic Force Microscopy
- 2019
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 418-419, s. 151-159
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how the composition of organic coatings influences their ability to resist surface damage during use remains a challenge. A relevant potential influence is that of cross-linking density. This parameter is frequently used for tailoring the mechanical properties of organic coatings and it manifests itself in terms of scratch resistance. However, the mechanisms that influence scratch resistance are not fully understood. From a thermodynamic perspective, wear of coatings is related to their ability to dissipate friction energy. Hence, it would be reasonable to assume that cross-linking influences the scratch resistance of coatings by influencing their viscoelasticity, as this is one of the parameters that define energy dissipation during shear. This hypothesis was investigated by studying two similar waterborne polyurethane coatings that have different cross-linking properties. The multiple abilities of Atomic Force Microscopy (AFM) were used to characterize the coatings’ scratch resistance, frictional properties, stiffness, adhesiveness and viscoelasticity. Significantly, it was found that monitoring the thermal noise of AFM cantilevers in contact with the coatings was sensitive enough to quantify the effects of cross-linking on their viscoelasticity. Based on this work, cross-linking is proposed to enhance scratch resistance by elastically storing, and eventually releasing, part of the mechanical energy that was transferred to the coatings during shear.
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| 18. |
- Hayashi, Mariko, et al.
(författare)
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In vitro characterization and osteoblast responses to nanostructured photocatalytic TiO2 coated surfaces.
- 2012
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 8:6, s. 2411-6
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the study were to characterize a nanostructured photoactive titanium dioxide (TiO(2)) coating and to compare the cellular response of human osteoblasts before and after ultraviolet (UV) irradiation of the coating. A specific nanostructured TiO(2) powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs, and was heat-treated thereafter. After topographical, chemical and photocatalytic property characterizations, human osteoblasts were cultured on the coated discs before and after UV irradiation. Cell morphology was evaluated by scanning electron microscopy (SEM), and cell viability was analysed by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. From the contact angle analysis, the wettability significantly improved after UV irradiation. The cultured cells were flattened with numerous elongated lammellipodia; however, no morphological differences were indicated between -UV and +UV surfaces. The MTT assay analysis showed that -UV surface presented significantly higher viability compared to the +UV surface except for one cell population group at 3h where there were no differences. The nanostructured photoactive TiO(2) surface improved its hydrophilicity by UV irradiation, however no enhancing effect in cell response was confirmed at the time tested compared to the non-irradiated surface.
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| 19. |
- Jimbo, Ryo, et al.
(författare)
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The biological response to three different nanostructures applied on smooth implant surfaces
- 2012
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Ingår i: Clinical Oral Implants Research. - Hoboken, USA : Wiley-Blackwell. - 0905-7161 .- 1600-0501. ; 23:6, s. 706-712
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate the biological effects of three calcium phosphate (CaP) coatings with nanostructures on relatively smooth implant surfaces.Material and methods: Stable CaP nanoparticle suspensions of different particle sizes and structures were coated onto implants by immersion and subsequent heat treatment. An uncoated implant was used as the control. After topographical and chemical characterizations, implants were randomly inserted into rabbit tibiae for removal torque (RTQ) testing. To confirm the biological reaction, implants were placed in the bilateral femurs of three rabbits.Results: The topographical characterization showed that each surface had different nanostructural characteristics and X-ray photon spectroscopy showed various CaP compositions. The control and test groups had different nanotopographies; however, the differences among the test groups were only significant for Surfaces B and C and the rest were insignificant. The RTQ tests showed significantly higher values in two test groups (Surface A and Surface C). Histologically, no adverse effects were seen in any group. Histomorphometrical evaluation showed comparable or better osseointegration along the implant threads in the test groups.Conclusion: The three different CaP coatings with nanostructures on the implant surfaces had enhancing effects on osseointegration. Along with the surface nanotopography, the CaP chemistry might have influenced the biological outcomes.
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| 20. |
- Kalimuthu, Palraj, et al.
(författare)
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Battery-free radio frequency wireless sensor for bacteria based on their degradation of gelatin-fatty acid composite films
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 381
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Tidskriftsartikel (refereegranskat)abstract
- Continuous and automated bacteria detection is pivotal for a myriad of biomedical, food safety and envi-ronmental applications. This work presents the fabrication of a prototype of a passive (battery-free) radio frequency sensor for wireless detection of bacteria. The sensing mechanism is based on the bacterial-induced (proteases and peptidases) degradation of glutaraldehyde (GTA) cross-linked gelatin-caprylic acid (CA) composite film. Proteolytic degradation of the film resulted in a decrease of its resistivity, a quan-tity that could be wirelessly monitored by coupling the film to a radio-frequency antenna (an inductor-capacitor resonator) and monitoring the frequency for which the transferred power between this antenna and another antenna connected to a Vector Network Analyzer (VNA) was maximized. We experimen-tally proved this concept by monitoring E.coli bacteria in aqueous medium and detected at 18.0 +/- 2.8 h, 23.5 +/- 0.7 h, 27.0 +/- 2.8 h, 40.5 +/- 3.5 h, 45.5 +/- 0.7 h for the initial E.coli concentration of 3.2 +/- 10(8) , 6.8 +/- 10(7) , 2.3 +/- 10(6) , 4.3 +/- 10(5) , and 3.6 +/- 10(4) CFU/mL, respectively. Further, the E.coli induced degrada-tion of the composite film was investigated by evaluating the thickness of the film by optical microscopy as well as morphology by scanning electron microscopy techniques. (C) 2021 Published by Elsevier Ltd.
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| 21. |
- Kalimuthu, Palraj, et al.
(författare)
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Highly Stable Passive Wireless Sensor for Protease Activity Based on Fatty Acid-Coupled Gelatin Composite Films.
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:19, s. 13110-13117
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Tidskriftsartikel (refereegranskat)abstract
- Proteases are often used as biomarkers of many pathologies as well as of microbial contamination and infection. Therefore, extensive efforts are devoted to the development of protease sensors. Some applications would benefit from wireless monitoring of proteolytic activity at minimal cost, e.g., sensors embedded in care products like wound dressings and diapers to track wound and urinary infections. Passive (batteryless) and chipless transponders stand out among wireless sensing technologies when low cost is a requirement. Here, we developed and extensively characterized a composite material that is biodegradable but still highly stable in aqueous media, whose proteolytic degradation could be used in these wireless transponders as a transduction mechanism of proteolytic activity. This composite material consisted of a cross-linked gelatin network with incorporated caprylic acid. The digestion of the composite when exposed to proteases results in a change of its resistivity, a quantity that can be wirelessly monitored by coupling the composite to an inductor-capacitor resonator, i.e., an antenna. We experimentally proved this wireless sensor concept by monitoring the presence of a variety of proteases in aqueous media. Moreover, we also showed that detection time follows a relationship with protease concentration, which enables quantification possibilities for practical applications.
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| 22. |
- Larpant, Nutcha, et al.
(författare)
-
Sensing by wireless reading Ag/AgCl redox conversion on RFID tag : universal, battery-less biosensor design
- 2019
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Massive integration of biosensors into design of Internet-of-Things (IoT) is vital for progress of healthcare. However, the integration of biosensors is challenging due to limited availability of battery-less biosensor designs. In this work, a combination of nanomaterials for wireless sensing of biological redox reactions is described. The design exploits silver nanoparticles (AgNPs) as part of the RFID tag antenna. We demonstrate that a redox enzyme, particularly, horseradish peroxidase (HRP), can convert AgNPs into AgCl in the presence of its substrate, hydrogen peroxide. This strongly changes the impedance of the tag. The presented example exploits gold nanoparticle (AuNP)-assisted electron transfer (ET) between AgNPs and HRP. We show that AuNP is a vital intermediate for establishing rapid ET between the enzyme and AgNPs. As an example, battery-less biosensor-RFID tag designs for H2O2 and glucose are demonstrated. Similar battery-less sensors can be constructed to sense redox reactions catalysed by other oxidoreductase enzymes, their combinations, bacteria or other biological and even non-biological catalysts. In this work, a fast and general route for converting a high number of redox reaction based sensors into battery-less sensor-RFID tags is described.
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| 23. |
- Lindh, Liselott, et al.
(författare)
-
Salivary pellicles
- 2014
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Ingår i: Saliva. - : S. Karger. - 9783318025958 - 9783318025965 ; , s. 30-39
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The salivary pellicle is a thin acellular organic film that forms on any type of surface upon exposure to saliva. The role of the pellicle is manifold, and it plays an important role in the maintenance of oral health. Its functions include not only substratum protection and lubrication, but also remineralization and hydration. It also functions as a diffusion barrier and possesses buffering ability. Not only the function, but also the formation, composition and stability of the pellicle are known to be highly influenced by the physicochemical properties of both substrata and ambient media. In this chapter, we discuss these aspects of salivary pellicles, an area where research has boomed in the past years partly because of the application of experimental techniques often reserved for more traditional surface science studies.
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| 24. |
- Luchini, Alessandra, et al.
(författare)
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Peptide Disc Mediated Control of Membrane Protein Orientation in Supported Lipid Bilayers for Surface-Sensitive Investigations
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:1, s. 1081-1088
-
Tidskriftsartikel (refereegranskat)abstract
- In vitro characterization of membrane proteins requires experimental approaches providing mimics of the microenvironment that proteins encounter in native membranes. In this context, supported lipid bilayers provide a suitable platform to investigate membrane proteins by a broad range of surface-sensitive techniques such as neutron reflectometry (NR), quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR), atomic force microscopy (AFM), and fluorescence microscopy. Nevertheless, the successful incorporation of membrane proteins in lipid bilayers with sufficiently high concentration and controlled orientation relative to the bilayer remains challenging. We propose the unconventional use of peptide discs made by phospholipids and amphipathic 18A peptides to mediate the formation of supported phospholipid bilayers with two different types of membrane proteins, CorA and tissue factor (TF). The membrane proteins are reconstituted in peptide discs, deposited on a solid surface, and the peptide molecules are then removed with extensive buffer washes. This leaves a lipid bilayer with a relatively high density of membrane proteins on the support surface. As a very important feature, the strategy allows membrane proteins with one large extramembrane domain to be oriented in the bilayer, thus mimicking the in vivo situation. The method is highly versatile, and we show its general applicability by characterizing with the above-mentioned surface-sensitive techniques two different membrane proteins, which were efficiently loaded in the supported bilayers with similar to 0.6% mol/mol (protein/lipid) concentration corresponding to 35% v/v for CorA and 8% v/v for TF. Altogether, the peptide disc mediated formation of supported lipid bilayers with membrane proteins represents an attractive strategy for producing samples for structural and functional investigations of membrane proteins and for preparation of suitable platforms for drug testing or biosensor development.
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| 25. |
- Madsen, Jan Busk, et al.
(författare)
-
Structural and Mechanical Properties of Thin Films of Bovine Submaxillary Mucin (BSM) vs. Porcine Gastric Mucin (PGM) on a Hydrophobic Surface in Aqueous Solutions
- 2016
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:38, s. 9687-9696
-
Tidskriftsartikel (refereegranskat)abstract
- The structural and mechanical properties of thin films generated from two types of mucins, namely, bovine submaxillary mucin (BSM) and porcine gastric mucin (PGM) in aqueous environment were investigated with several bulk and surface analytical techniques. Both mucins generated hydrated films on hydrophobic polydimethylsiloxane (PDMS) surfaces from spontaneous adsorption arising from their amphiphilic characteristic. However, BSM formed more elastic films than PGM at neutral pH condition. This structural difference was manifested from the initial film formation processes to the responses to shear stresses applied to the films. Acidification of environmental pH led to strengthening the elastic character of BSM films with increased adsorbed mass, whereas an opposite trend was observed for PGM films. We propose that this contrast originates from that negatively charged motifs are present for both the central and terminal regions of BSM molecule, whereas a similar magnitude of negative charges is localized at the termini of PGM molecule. Given that hydrophobic motifs acting as an anchor are also localized in the terminal region, electrostatic repulsion between anchoring units of PGM molecules on a nonpolar PDMS surface leads to weakening of the mechanical integrity of the films.
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| 26. |
- Pankratov, Dmitry, et al.
(författare)
-
Interfacial behavior and activity of laccase and bilirubin oxidase on bare gold surfaces
- 2014
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:10, s. 2943-2951
-
Tidskriftsartikel (refereegranskat)abstract
- Two blue multicopper oxidases (MCOs) (viz. Trametes hirsuta laccase (ThLc) and Myrothecium verrucaria bilirubin oxidase (MvBOx)) were immobilized on bare polycrystalline gold (Au) surfaces by direct adsorption from both dilute and concentrated enzyme solutions. The adsorption was studied in situ by means of null ellipsometry. Moreover, both enzyme-modified and bare Au electrodes were investigated in detail by atomic force microscopy (AFM) as well as electrochemically. When adsorbed from dilute solutions (0.125 and 0.25 mg mL–1 in the cases of ThLc and MvBOx, respectively), the amounts of enzyme per unit area were determined to be ca. 1.7 and 4.8 pmol cm–2, whereas the protein film thicknesses were determined to be 29 and 30 Å for ThLc and MvBOx, respectively. A well-pronounced bioelectrocatalytic reduction of molecular oxygen (O2) was observed on MvBOx/Au biocathodes, whereas this was not the case for ThLc-modified Au electrodes (i.e., adsorbed ThLc was catalytically inactive). The initially observed apparent kcatapp values for adsorbed MvBOx and the enzyme in solution were found to be very close to each other (viz. 54 and 58 s–1, respectively (pH 7.4, 25 °C)). However, after 3 h of operation of MvBOx/Au biocathodes, kcatapp dropped to 23 s–1. On the basis of the experimental results, conformational changes of the enzymes (in all likelihood, their flattening on the Au surface) were suggested to explain the deactivation of MCOs on the bare Au electrodes.
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| 27. |
- Pankratov, Dmitry, et al.
(författare)
-
Scalable, high performance, enzymatic cathodes based on nanoimprint lithography
- 2015
-
Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 6, s. 1377-1384
-
Tidskriftsartikel (refereegranskat)abstract
- Here we detail high performance, enzymatic electrodes for oxygen bio-electroreduction, which can be easily and reproducibly fabricated with industry-scale throughput. Planar and nanostructured electrodes were built on biocompatible, flexible polymer sheets, while nanoimprint lithography was used for electrode nanostructuring. To the best of our knowledge, this is one of the first reports concerning the usage of nanoimprint lithography for amperometric bioelectronic devices. The enzyme (Myrothecium verrucaria bilirubin oxidase) was immobilised on planar (control) and artificially nanostructured, gold electrodes by direct physical adsorption. The detailed electrochemical investigation of bioelectrodes was performed and the following parameters were obtained: open circuit voltage of approximately 0.75 V, and maximum bio-electrocatalytic current densities of 18 mu A/cm(2) and 58 mu A/cm(2) in air-saturated buffers versus 48 mu A/cm(2) and 186 mu A/cm(2) in oxygen-saturated buffers for planar and nanostructured electrodes, respectively. The half-deactivation times of planar and nanostructured biocathodes were measured to be 2 h and 14 h, respectively. The comparison of standard heterogeneous and bio-electrocatalytic rate constants showed that the improved bio-electrocatalytic performance of the nanostructured biocathodes compared to planar biodevices is due to the increased surface area of the nanostructured electrodes, whereas their improved operational stability is attributed to stabilisation of the enzyme inside nanocavities.
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| 28. |
- Pankratov, Dmitry, et al.
(författare)
-
The influence of nanoparticles on enzymatic bioelectrocatalysis
- 2014
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 4:72, s. 38164-38168
-
Tidskriftsartikel (refereegranskat)abstract
- In nearly all papers concerning enzyme–nanoparticle based bioelectronic devices, it is stated that the presence of nanoparticles on electrode surfaces per se enhances bioelectrocatalysis, although the reasons for that enhancement are often unclear. Here, we report detailed experimental evidence that neither an overpotential of bioelectrocatalysis, nor direct electron transfer and bioelectrocatalytic reaction rates for an adsorbed enzyme depend on the size of nanoparticles within the range of 20–80 nm, i.e. for nanoparticles that are considerably larger than the enzyme molecules.
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| 29. |
- Pankratov, Dmitry, et al.
(författare)
-
The influence of nanoparticles on enzymatic bioelectrocatalysis
- 2014
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:72, s. 38164-38168
-
Tidskriftsartikel (refereegranskat)abstract
- In nearly all papers concerning enzyme-nanoparticle based bio-electronic devices, it is stated that the presence of nanoparticles on electrode surfaces per se enhances bioelectrocatalysis, although the reasons for that enhancement are often unclear. Here, we report detailed experimental evidence that neither an overpotential of bioelectrocatalysis, nor direct electron transfer and bioelectrocatalytic reaction rates for an adsorbed enzyme depend on the size of nanoparticles within the range of 20-80 nm, i.e. for nanoparticles that are considerably larger than the enzyme molecules.
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| 30. |
- Pankratov, Dmitry, et al.
(författare)
-
Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells
- 2015
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 1873-2755 .- 0378-7753. ; 294, s. 501-506
-
Tidskriftsartikel (refereegranskat)abstract
- Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved.
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| 31. |
- Psotta, Carolin, et al.
(författare)
-
Portable Prussian Blue-Based Sensor for Bacterial Detection in Urine
- 2023
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 23:1
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial infections can affect the skin, lungs, blood, and brain, and are among the leading causes of mortality globally. Early infection detection is critical in diagnosis and treatment but is a time- and work-consuming process taking several days, creating a hitherto unmet need to develop simple, rapid, and accurate methods for bacterial detection at the point of care. The most frequent type of bacterial infection is infection of the urinary tract. Here, we present a wireless-enabled, portable, potentiometric sensor for E. coli. E. coli was chosen as a model bacterium since it is the most common cause of urinary tract infections. The sensing principle is based on reduction of Prussian blue by the metabolic activity of the bacteria, detected by monitoring the potential of the sensor, transferring the sensor signal via Bluetooth, and recording the output on a laptop or a mobile phone. In sensing of bacteria in an artificial urine medium, E. coli was detected in similar to 4 h (237 +/- 19 min; n = 4) and in less than 0.5 h (21 +/- 7 min, n = 3) using initial E. coli concentrations of similar to 10(3) and 10(5) cells mL(-1), respectively, which is under or on the limit for classification of a urinary tract infection. Detection of E. coli was also demonstrated in authentic urine samples with bacteria concentration as low as 10(4) cells mL(-1), with a similar response recorded between urine samples collected from different volunteers as well as from morning and afternoon urine samples.
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| 32. |
- Rajendran, Sriram Thoppe, et al.
(författare)
-
Tissue-based biosensor for monitoring the antioxidant effect of orally administered drugs in the intestine
- 2020
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 138
-
Tidskriftsartikel (refereegranskat)abstract
- For a better understanding of the effect of drugs and their interaction with cells and tissues, there is a need for in vitro and ex vivo model systems which enables studying these events. There are several in vitro methods available to evaluate the antioxidant activity; however, these methods do not factor in the complex in vivo physiology. Here we present an intestinal tissue modified oxygen electrode, used for the detection of the antioxidant effect of orally administered drugs in the presence of H2O2. Antioxidants are essential in the defense against oxidative stress, more specifically against reactive oxygen species such as H2O2. Due to the presence of native catalase in the intestine, with the tissue-based biosensor we were able to detect H2O2 in the range between 50 and 500 µM. The reproducibility of the sensor based on the calculated relative standard deviations was 15 ± 6%. We found that the O2 production by catalase from H2O2 was reduced in the presence of a well-known antioxidant, quinol. This indirectly detected antioxidant activity was also observed in the case of orally administered drugs with a reported anti-inflammatory effect such as mesalazine and paracetamol, while no antioxidant activity was recorded with aspirin and metformin.
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| 33. |
- Ruzgas, Tautgirdas, et al.
(författare)
-
Wireless, Battery-less Biosensors Based on Direct Electron Transfer Reactions
- 2019
-
Ingår i: ChemElectroChem. - : John Wiley & Sons. - 2196-0216. ; 6:20, s. 5167-5171
-
Forskningsöversikt (refereegranskat)abstract
- Studies of direct electron transfer (DET) between enzymes and electrodes, among other reasons, are aimed at designing the simplest and most efficient biosensor designs. This direction might become especially valuable for the widespread integration of biosensors in Internet-of-Things (IoT) networks. In this Minireview, the simplicity of the design of wireless biosensors based on DET is discussed. It can be concluded that DET allows construction of wireless biosensors, which require no or only a few semiconductor elements. Hopefully, some of these demonstrations will translate into competitive and useful devices strongly promoting biosensing in IoT networks.
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| 34. |
- Shafaat, Atefeh, et al.
(författare)
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A Rapidly Responsive Sensor for Wireless Detection of Early and Mature Microbial Biofilms.
- 2023
-
Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:40
-
Tidskriftsartikel (refereegranskat)abstract
- Biofilm-associated infections, which are able to resist antibiotics, pose a significant challenge in clinical treatments. Such infections have been linked to various medical conditions, including chronic wounds and implant-associated infections, making them a major public-health concern. Early-detection of biofilm formation offers significant advantages in mitigating adverse effects caused by biofilms. In this work, we aim to explore the feasibility of employing a novel wireless sensor for tracking both early-stage and matured-biofilms formed by the medically relevant bacteria Staphylococcus aureus and Pseudomonas aeruginosa. The sensor utilizes electrochemical reduction of an AgCl layer bridging two silver legs made by inkjet-printing, forming a part of near-field-communication tag antenna. The antenna is interfaced with a carbon cloth designed to promote the growth of microorganisms, thereby serving as an electron source for reduction of the resistive AgCl into a highly-conductive Ag bridge. The AgCl-Ag transformation significantly alters the impedance of the antenna, facilitating wireless identification of an endpoint caused by microbial growth. To the best of our knowledge, this study for the first time presents the evidence showcasing that electrons released through the actions of bacteria can be harnessed to convert AgCl to Ag, thus enabling the wireless, battery-less, and chip-less early-detection of biofilm formation.
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| 35. |
- Shafaat, Atefeh
(författare)
-
Development of Wireless Biosensors Integrated into the Radio Frequency Antenna for Chipless and Battery-less Monitoring of Biological Reactions
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Development of wireless sensors and biosensors is currently experiencing a rapid progress with a substantial focus directed toward highlighting their potential applications as non-invasive wearables, implants, and highly mobile point-of-care devices. Integration of wireless biosensors into the Internet of Things (IoT) is widely acknowledged as a technological advancement with the potential to significantly change daily life. To maximize this potential, simple integration of biosensors with wireless communication elements would be advantageous. In this regard, systems functioning in chipless, and battery-less modes outperform integrated circuit (IC) based and battery-powered wireless biosensors. Nevertheless, the accessibility of these wireless designs is still limited. In this study, we present a novel approach where incorporating silver nanoparticles(AgNPs) as a part of the radio frequency (RF) tag antenna enables the realization of simple, chipless, and battery-less wireless sensing of biological oxidation and reduction reactions. We exemplified the mechanism of operation in such systems by electronic wiring of enzymes through direct electron transfer (DET) and microorganisms through mediated electron transfer (MET) to the redox conversion of Ag/AgCl. The wiring was designed to facilitate the transformation of metallic AgNPs into AgCl (Ag → AgCl) or the conversion of AgCl particles back into metallic AgNPs (AgCl → Ag) when the enzymatic/microorganism based electron transfer reactions were present. These reactions occurring on the biosensor RF tag antenna strongly changed the impedance of the tag, which was wirelessly monitored by a radio frequency identification (RFID) reader. The functionality of the proposed setup in direct electron transfer coupling of the enzymatic reactions to the redox conversion of the Ag/AgCl was demonstrated by wireless detection of glucose in whole blood samples and hydrogen peroxide penetrated through the skin membrane using the enzymes glucose dehydrogenase(GDH) and horseradish peroxidase (HRP). Additionally, the capability of the proposed configuration in mediated electron transfer wiring of microorganisms to the Ag/AgCl electrochemistry was shown by wireless monitoring of medically relevant microbial biofilms in simulated wound fluid. Generalizing, the results of this work, for the first time, demonstrated that exploiting Ag/AgCl as a part of the tag antenna allows simple, chipless, and battery-less wireless sensing of biological oxidation and reduction reactions.
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| 36. |
- Shafaat, Atefeh, et al.
(författare)
-
Glucose-to-Resistor Transduction Integrated into a Radio-Frequency Antenna for Chip-less and Battery-less Wireless Sensing
- 2022
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 7:4, s. 1222-1234
-
Tidskriftsartikel (refereegranskat)abstract
- To maximize the potential of 5G infrastructure in healthcare, simple integration of biosensors with wireless tag antennas would be beneficial. This work introduces novel glucose-to-resistor transduction, which enables simple, wireless biosensor design. The biosensor was realized on a near-field communication tag antenna, where a sensing bioanode generated electrical current and electroreduced a nonconducting antenna material into an excellent conductor. For this, a part of the antenna was replaced by a Ag nanoparticle layer oxidized to high-resistance AgCl. The bioanode was based on Au nanoparticle-wired glucose dehydrogenase (GDH). The exposure of the cathode-bioanode to glucose solution resulted in GDH-catalyzed oxidation of glucose at the bioanode with a concomitant reduction of AgCl to highly conducting Ag on the cathode. The AgCl-to-Ag conversion strongly affected the impedance of the antenna circuit, allowing wireless detection of glucose. Mimicking the final application, the proposed wireless biosensor was ultimately evaluated through the measurement of glucose in whole blood, showing good agreement with the values obtained with a commercially available glucometer. This work, for the first time, demonstrates that making a part of the antenna from the AgCl layer allows achieving simple, chip-less, and battery-less wireless sensing of enzyme-catalyzed reduction reaction.
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| 37. |
- Sotres, Javier, et al.
(författare)
-
Adsorption and nanowear properties of bovine submaxillary mucin films on solid surfaces : influence of solution pH and substrate hydrophobicity
- 2014
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 428, s. 242-250
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption and mechanical stability of bovine submaxillary mucins (BSM) films at solid–liquid interfaces were studied with respect to both substrate hydrophobicity and solution pH. Dynamic light scattering revealed a single peak distribution in neutral aqueous solution (pH 7.4) and a small fraction with enhanced aggregation was observed in acidic solution (pH 3.8). Both substrate hydrophobicity and solution pH were found to affect the spontaneous adsorption of BSM onto solid surfaces; BSM adsorbed more onto hydrophobic surfaces than hydrophilic ones, and adsorbed more at pH 3.8 than at pH 7.4. Thus, the highest “dry” adsorbed mass was observed for hydrophobic surfaces in pH 3.8 solution. However, a highest “wet” adsorbed mass, i.e. which includes the solvent coupled to the film, was observed for hydrophobic surfaces at pH 7.4. The mechanical stability of the films was studied at the nanoscale with an atomic force microscope operated in the friction force spectroscopy mode. Results revealed that BSM films formed on hydrophobic substrates were stronger than those formed on hydrophilic ones. Moreover, the film stability also depended on the ambient pH and stronger films were formed at acidic conditions, i.e. close to the BSM isoelectric point.
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| 38. |
- Sotres, Javier, et al.
(författare)
-
AFM-based friction force spectroscopy : a novel methodology for the study of the strength and lateral diffusion of proteinaceous films
- 2012
-
Ingår i: Proteins at Interfaces III State of the Art. - Washington, DC : American Chemical Society (ACS). - 9780841227972 - 9780841227965 ; , s. 129-151
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We present a novel methodology for the study of proteinaceous films based on the friction force spectroscopy operation mode of the atomic force microscope. It provides information both on the strength at the nanoscale level and on the lateral diffusion properties of these systems. The usefulness of the data generated by this methodology are shown through its application to the study of different types of monolayers of model proteins, as well as to the study of the more complex and heterogeneous salivary films.
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| 39. |
- Sotres, Javier
(författare)
-
Biopolymers in the Prevention of Dental Erosion
- 2016
-
Ingår i: Biopolymers for Medical Applications. - Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 : CRC Press. - 9781498744966 ; , s. 101-116
-
Bokkapitel (refereegranskat)abstract
- Dental erosion, that is, the loss of dental hard tissue induced by acids of non-bacterial origin, is currently recognized in many Western countries as the main factor responsible for tooth wear. Dental erosion results not only in aesthetic, orthodontic, and functional complications, but is also associated with sensitivity and pain. Its prevalence has become alarmingly high and continues to escalate. As a consequence, it is expected that dental erosion will have a major economic impact on dental services in the decades to come. Thus, it is not daring to place dental erosion as one of the biggest challenges in dentistry for the 21st century. It is difficult to both diagnose dental erosion in early stages and to treat it in advanced stages. Thus, a considerable effort has been devoted to the development of prevention strategies. At present, most of such strategies focus on increasing the acid-resistance of the dentition and on weakening the erosive potential of erosive challenges, for example, acidic foods and beverages. Recently, it has been shown that different types of biopolymers can be used for these purposes. If topically applied, biopolymers can adsorb on teeth increasing their acid-resistance. Additionally, the erosiveness of acidic beverages can be lowered if modified with biopolymers. Biopolymers present additional advantages over other anti-erosive compounds, for example, they do not possess health risks and, as expected from their wide use in the food industry, they may rise low consumer-acceptance concerns. This chapter aims at providing an overview of the potential of biopolymers in the prevention of dental erosion.
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| 40. |
- Sotres, Javier, et al.
(författare)
-
Enabling autonomous scanning probe microscopy imaging of single molecules with deep learning
- 2021
-
Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 13:20, s. 9193-9203
-
Tidskriftsartikel (refereegranskat)abstract
- Scanning probe microscopies allow investigating surfaces at the nanoscale, in real space and with unparalleled signal-to-noise ratio. However, these microscopies are not used as much as it would be expected considering their potential. The main limitations preventing a broader use are the need of experienced users, the difficulty in data analysis and the time-consuming nature of experiments that require continuous user supervision. In this work, we addressed the latter and developed an algorithm that controlled the operation of an Atomic Force Microscope (AFM) that, without the need of user intervention, allowed acquiring multiple high-resolution images of different molecules. We used DNA on mica as a model sample to test our control algorithm, which made use of two deep learning techniques that so far have not been used for real time SPM automation. One was an object detector, YOLOv3, which provided the location of molecules in the captured images. The second was a Siamese network that could identify the same molecule in different images. This allowed both performing a series of images on selected molecules while incrementing the resolution, as well as keeping track of molecules already imaged at high resolution, avoiding loops where the same molecule would be imaged an unlimited number of times. Overall, our implementation of deep learning techniques brings SPM a step closer to full autonomous operation.
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| 41. |
- Sotres, Javier, et al.
(författare)
-
Ex-Vivo Force Spectroscopy of Intestinal Mucosa Reveals the Mechanical Properties of Mucus Blankets
- 2017
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Mucus is the viscous gel that protects mucosal surfaces. It also plays a crucial role in several diseases as well as in mucosal drug delivery. Because of technical limitations, mucus properties have mainly been addressed by in-vitro studies. However, this approach can lead to artifacts as mucus collection can alter its structure. Here we show that by using an implemented atomic force microscope it is possible to measure the interactions between micro-particles and mucus blankets ex-vivo i.e., on fresh excised mucus-covered tissues. By applying this method to study the small intestine, we were able to quantify the stiffness and adhesiveness of its mucus blanket at different pH values. We also demonstrate the ability of mucus blankets to bind and attract particles hundreds of µm away from their surface, and to trap and bury them even if their size is as big as 15 µm.
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| 42. |
- Sotres, Javier, et al.
(författare)
-
Experimental Investigations of Biological Lubrication at the Nanoscale : The Cases of Synovial Joints and the Oral Cavity
- 2013
-
Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 1:4, s. 102-131
-
Forskningsöversikt (refereegranskat)abstract
- Interactions between surfaces are ubiquitous phenomena in living organisms. Nature has developed sophisticated strategies for lubricating these systems, increasing their efficiency and life span. This includes the use of water-based lubricants, such as saliva and synovial fluid. These fluids overcome the limitations of water as a lubricant by the presence of molecules such as proteins, lipids, and polysaccharides. Such molecules may alter surface interactions through different mechanisms. They can increase viscosity enabling fluid-film lubrication. Moreover, molecules adsorb on the surfaces providing mechanisms for boundary lubrication and preventing wear. The mentioned molecules have typical sizes in the nanometer range. Their interaction, as well as the interaction with the entrapping surfaces, takes place through forces in the range of nanonewtons. It is therefore not surprising that the investigation of these systems have been boosted by development of techniques such as scanning probe microscopies and the surface force apparatus which allow studying tribological processes at the nanoscale. Indeed, these approaches have generated an enormous amount of studies over the last years. The aim of this review is to perform a critical analysis of the current stage of this research, with a main focus on studies on synovial joints and the oral cavity.
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| 43. |
- Sotres, Javier, et al.
(författare)
-
Friction Force Spectroscopy as a Tool to Study the Strength and Lateral Diffusion of Protein Layers
- 2011
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:15, s. 9439-9448
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to study the strength of layers of biological molecules in liquid medium. The method is based on the Friction Force Spectroscopy operation mode of the Atomic Force Microscope. It works by scratching the sample surface at different applied loads while registering the evolution of the sample topography and of the friction between probe and sample. Results are presented for BSA and β-casein monolayers on hydrophobic surfaces. We show how the simultaneous monitoring of topography and friction allows detecting differences not only between the strength of both types of layers, but also between the lateral diffusion of the proteins within these layers. Specifically, β-casein is shown to form stronger layers than BSA. The yield strengths calculated for both of these systems are in the range 50-70 MPa. Moreover, while no lateral diffusion is observed for BSA, we show that β-casein diffuses along the hydrophobic substrates at a rate higher than the scan velocity of the tip (16 μm s(-1) in our case).
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| 44. |
- Sotres, Javier, et al.
(författare)
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Friction Force Spectroscopy as a Tool to Study the Strength and Structure of Salivary Films
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:22, s. 13692-13700
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we employ atomic force microscopy based friction force spectroscopy to study the strength and structure of salivary films. Specifically, films formed on model hydrophobic (methylated silica) and hydrophilic (clean silica) substrata have been studied in water at pHs in the range 3.3–7. Results reveal that films formed on both types of substrata can be described in terms of two different fractions, with only one of them being able to diffuse along the underlying substrata. We also show how the protective function of the films is reduced when the pH of the surrounding medium is lowered. Specifically, lowering of pH causes desorption of some components of the films formed on hydrophobic methylated surfaces, leading to weaker layers. In contrast, at low pHs, saliva no longer forms a layer on hydrophilic silica surfaces. Instead, an inhomogeneous distribution of amorphous aggregates is observed. Our data also suggest that hydrophobic materials in the oral cavity might be more easily cleaned from adsorbed salivary films. Finally, reproducible differences are observed in results from experiments on films from different individuals, validating the technique as a tool for clinical diagnosis of the resistance to erosion of salivary films.
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| 45. |
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| 46. |
- Sotres, Javier, et al.
(författare)
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Friction Force Spectroscopy of β- and κ-casein monolayers
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:3, s. 981-992
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Tidskriftsartikel (refereegranskat)abstract
- Friction force spectroscopy (FFS) has been applied to study the tribological properties of β- and κ-casein layers on hydrophobic substrates in aqueous solutions. Nanometer-sized imaging tips were employed. This allowed exerting and determining the high pressures needed to remove the layers, and registering the topographic evolution during this process. Both β- and κ-casein layers showed similar and not particularly high initial frictional responses (friction coefficient of ~1 when measure with a silicon nitride tip). The pressures needed to remove the layers were of the same order of magnitude for both proteins, ~1e8 Pa, but slightly higher for those composed of β-casein. The technique has also shown to be useful in studying the two-dimensional lateral diffusion of the proteins and the wear on the layers they form.
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| 47. |
- Sotres, Javier, et al.
(författare)
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Locating critical events in AFM force measurements by means of one-dimensional convolutional neural networks.
- 2022
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Atomic Force Microscopy (AFM) force measurements are a powerful tool for the nano-scale characterization of surface properties. However, the analysis of force measurements requires several processing steps. One is locating different type of events e.g., contact point, adhesions and indentations. At present, there is a lack of algorithms that can automate this process in a reliable way for different types of samples. Moreover, because of their stochastic nature, the acquisition and analysis of a high number of force measurements is typically required. This can result in these experiments becoming an overwhelming task if their analysis is not automated. Here, we propose a Machine Learning approach, the use of one-dimensional convolutional neural networks, to locate specific events within AFM force measurements. Specifically, we focus on locating the contact point, a critical step for the accurate quantification of mechanical properties as well as long-range interactions. We validate this approach on force measurements obtained both on hard and soft surfaces. This approach, which could be easily used to also locate other events e.g., indentations and adhesions, has the potential to significantly facilitate and automate the analysis of AFM force measurements and, therefore, the use of this technique by a wider community.
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| 48. |
- Sotres, Javier, et al.
(författare)
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NanoWear of Salivary Films vs. Substratum Wettability
- 2012
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Ingår i: Journal of Dental Research. - : SAGE Publications. - 0022-0345 .- 1544-0591. ; 91:10, s. 973-978
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Tidskriftsartikel (refereegranskat)abstract
- The pellicle serves as a multifunctional protective layer, providing, e.g., lubrication and remineralization and also acting as a diffusion barrier. In addition, since the formation of the pellicle precedes the adhesion of micro-organisms, it is also important as a conditioning film. We present a novel approach to study the influence of the water wettability of solid surfaces on the strength of adsorbed salivary films. It is based on studying the wear resistance of the films with an atomic force microscope operated in the friction force spectroscopy mode. This methodology provides the strength of the films in terms of the forces needed for breaking and removing them. Our results indicate that these forces are highly dependent on the water wettability of the underlying substrata, decreasing with increasing hydrophobicity. Thus, this study provides valuable information for the design of materials exposed in the oral cavity, i.e., materials that will minimize plaque formation and be easy to clean.
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| 49. |
- Sotres, Javier, et al.
(författare)
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Strategies for a Direct Characterization of Phosphoproteins on Hydroxyapatite Surfaces
- 2014
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Ingår i: Caries Research. - : S. Karger. - 0008-6568 .- 1421-976X. ; 48:2, s. 98-110
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Tidskriftsartikel (refereegranskat)abstract
- We show in this work how systems formed by phosphoproteins on calcium phosphate surfaces can be directly characterized, in real time, in liquid medium, without the need for elution or labeling. Specifically, we show how this is possible by applying three different techniques: ellipsometry, quartz crystal microbalance with dissipation, and atomic force microscopy-based friction force spectroscopy. We apply these techniques to study two different model systems, i.e. those formed upon the adsorption of two model phosphoproteins (κ- and β-casein) on hydroxyapatite (HA) surfaces. Information on the kinetics of adsorption, surface excess, viscoelasticity, water content, thickness of the layers, and protein-surface interaction is provided. Results indicate that both phosphoproteins form homogeneous elastic highly hydrated monolayers on the HA surfaces, the strength of β-casein layers being higher by approximately a factor of 4. Based on the experimental results, models for the conformation of κ- and β-casein molecules adsorbed on HA surfaces are proposed.
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| 50. |
- Svendsen, Ida, et al.
(författare)
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Adsorption of HSA, IgG and laminin-1 on model hydroxyapatite surfaces - effects of surface characteristics
- 2012
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Ingår i: Biofouling (Print). - : Taylor & Francis. - 0892-7014 .- 1029-2454. ; 28:1, s. 87-97
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Tidskriftsartikel (refereegranskat)abstract
- Ellipsometry and mechanically assisted sodium dodecyl sulphate elution was utilized to study the adsorption of human serum albumin (HSA), human immunoglobulin G (IgG), and laminin-1, as well as competitive adsorption from a mixture of these proteins on spin-coated and sintered hydroxyapatite (HA) surfaces, respectively. The HA surfaces were characterized with respect to wettability and roughness by means of water contact angles and atomic force microscopy, respectively. Both surface types were hydrophilic, and the average roughness (Sa) and surface enlargement (Sdr) were lower for the sintered compared to the spin-coated HA surfaces. The adsorbed amounts on the sintered HA increased as follows: HSA < laminin-1 < IgG < the protein mixture. For the competitive adsorption experiments, the adsorbed fractions increased accordingly: HSA < laminin-1 < IgG on both types of HA substratum. However, a higher relative amount of HSA and laminin-1 and a lower relative amount of IgG was found on the spin-coated surfaces compared to the sintered surfaces. The effects observed could be ascribed to differences in surface roughness and chemical composition between the two types of HA substratum, and could have an influence on selection of future implant surface coatings.
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