| 1. |
- Pandit, Santosh, 1987, et al.
(författare)
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Low Concentrations of Vitamin C Reduce the Synthesis of Extracellular Polymers and Destabilize Bacterial Biofilms
- 2017
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular polymeric substances (EPS) produced by bacteria form a matrix supporting the complex three-dimensional architecture of biofilms. This EPS matrix is primarily composed of polysaccharides, proteins and extracellular DNA. In addition to supporting the community structure, the EPS matrix protects bacterial biofilms from the environment. Specifically, it shields the bacterial cells inside the biofilm, by preventing antimicrobial agents from getting in contact with them, thereby reducing their killing effect. New strategies for disrupting the formation of the EPS matrix can therefore lead to a more efficient use of existing antimicrobials. Here we examined the mechanism of the known effect of vitamin C (sodium ascorbate) on enhancing the activity of various antibacterial agents. Our quantitative proteomics analysis shows that non-lethal concentrations of vitamin C inhibit bacterial quorum sensing and other regulatory mechanisms underpinning biofilm development. As a result, the EPS biosynthesis in reduced, and especially the polysaccharide component of the matrix is depleted. Once the EPS content is reduced beyond a critical point, bacterial cells get fully exposed to the medium. At this stage, the cells are more susceptible to killing, either by vitamin C-induced oxidative stress as reported here, or by other antimicrobials or treatments.
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| 2. |
- Avaz, S., et al.
(författare)
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Graphene based nanosensor for aqueous phase detection of nitroaromatics
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 7:41, s. 25519-25527
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Tidskriftsartikel (refereegranskat)abstract
- A graphene-based nanosensor was fabricated to selectively detect nitrotriazolone (NTO) molecules with a molecularly imprinted film via simple electrical measurements. Molecularly imprinted polymer comprising chitosan was used as sensitive layer. Gold electrodes for electrical measurements were lithographically fabricated on Si/SiO2 substrate, followed by monolayer graphene transfer and polymeric film coating. Monolayer graphene and molecularly imprinted polymer were characterized by ATR-FTIR, UV-Vis, SEM and Raman spectroscopy. Transfer-length measurements (TLM) indicate that the sensor selectively and linearly responds against aqueous NTO solutions within a wide range of concentration of 0.01-0.1 mg mL(-1) that covers the lowest toxic level of NTO determined by USEPA. This nanosensor with embedded electrodes is re-usable and suitable for field applications, offering real-time electrical measurements unlike current techniques where complex analytics are required.
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| 3. |
- Cantatore, Valentina, 1986, et al.
(författare)
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Design strategy of a graphene based bio-sensor for glucose
- 2018
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 137, s. 343-348
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Tidskriftsartikel (refereegranskat)abstract
- A novel graphene-based glucose sensor-design is formulated and explored in silico. An ad hoc host molecule is tailored to bind to glucose by multiple hydrogen bonds. A pyridinic core is chosen for this receptor in order to allow for “socket-plug” dative bonding to boron sites of boron doped graphene. The modeling employs DFT (Density Functional Theory) together with an effective aqueous environment to take into account the solvation effect. High selectivity is demonstrated for the suggested host molecule towards glucose as compared to other possible competitors in blood such as fructose, biotin and ascorbic acid. A route to achieve improved sensitivity, exploiting the hydrophilic/hydrophobic properties of the host + glucose system for enhanced selective binding to the hydrophobic boron doped graphene support is discussed.
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| 4. |
- Helgadóttir, Saga Huld, 1991, et al.
(författare)
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Vitamin C Pretreatment Enhances the Antibacterial Effect of Cold Atmospheric Plasma
- 2017
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Ingår i: Frontiers in cellular and infection microbiology. - : Frontiers Media SA. - 2235-2988. ; 7:FEB
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial biofilms are three-dimensional structures containing bacterial cells enveloped in a protective polymeric matrix, which renders them highly resistant to antibiotics and the human immune system. Therefore, the capacity to make biofilms is considered as a major virulence factor for pathogenic bacteria. Cold Atmospheric Plasma (CAP) is known to be quite efficient in eradicating planktonic bacteria, but its effectiveness against biofilms has not been thoroughly investigated. The goal of this study was to evaluate the effect of exposure of CAP against mature biofilm for different time intervals and to evaluate the effect of combined treatment with vitamin C. We demonstrate that CAP is not very effective against 48 h mature bacterial biofilms of several common opportunistic pathogens: Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. However, if bacterial biofilms are pre-treated with vitamin C for 15 min before exposure to CAP, a significantly stronger bactericidal effect can be obtained. Vitamin C pretreatment enhances the bactericidal effect of cold plasma by reducing the viability from 10 to 2% in E. coli biofilm, 50 to 11% in P. aeruginosa, and 61 to 18% in S. epidermidis biofilm. Since it is not feasible to use extended CAP treatments in medical practice, we argue that the pre-treatment of infectious lesions with vitamin C prior to CAP exposure can be a viable route for efficient eradication of bacterial biofilms in many different applications.
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| 5. |
- Mokkapati, Venkata Raghu, 1981, et al.
(författare)
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Membrane properties and anti-bacterial/anti-biofouling activity of polysulfone-graphene oxide composite membranes phase inversed in graphene oxide non-solvent
- 2017
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Ingår i: RSC Advances. - 2046-2069. ; 7:8, s. 4378-4386
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Tidskriftsartikel (refereegranskat)abstract
- A new and facile method for the fabrication of polysulfone-graphene oxide composite membranes is reported, where after casting, phase inversion is carried out with graphene oxide flakes (GO) in a coagulation bath. The membranes were characterized and the morphology was analysed using scanning electron microscopy. A bacterial inhibition ratio of 74.5% was observed with membranes fabricated from a very low concentration of di-water-GO non-solvent (0.048% of GO). The membranes were successfully tested for permeate flux and fouling resistance using activated sludge filtration from an MBR system. The observed trend shows that GO can operate as a protective barrier for membrane pores against the bacterial community. To our knowledge this is the first time where the immersion precipitation mechanism was carried out in a coagulation bath with GO flakes under continuous stirring. Using this method, a very low concentration of GO is required to fabricate membranes with conventional GO composite membrane properties and better selectivity. © The Royal Society of Chemistry.
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| 6. |
- Mokkapati, Venkata Raghu, 1981, et al.
(författare)
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NaB integrated graphene oxide membranes for enhanced cell viability and stem cell properties of human adipose stem cells
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:61, s. 56159-56165
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Tidskriftsartikel (refereegranskat)abstract
- Here we present the integration of boron (NaB) with graphene oxide (GO) to develop a new class of membranes which are biocompatible and cost-effective for cell and tissue culture studies. Ethanol (EtOH) assisted the uniform dispersion of GO flakes on top of a glass substrate. We investigated the effect of a GO + NaB membrane on the growth and proliferation of hASCs. hASCs showed better cell viability on NaB integrated GO membranes compared to their respective controls. The concentrations of NaB and GO are 0.02% and 1/20 of stock (0.024%) respectively. To our knowledge this is the first time that enhanced cell proliferation and attachment ability of hASCs with NaB integrated GO membranes has been observed. Our study provides a platform for the development of 3D-GO scaffold systems combined with NaB in tissue engineering.
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| 7. |
- Pandit, Santosh, 1987, et al.
(författare)
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Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- The key first step in developing bacterial infections related to implants and medical devices is the attachment of planktonic bacterial cells, and subsequent formation of biofilms. Herein, it is reported that graphene, a 2D carbon-based material, can be effectively used to prevent bacterial attachment. The key parameter for this effect is the orientation of graphene with respect to the coated surface. Chemical vapor deposition (CVD) graphene, deposited horizontally on the surface, exhibits no antibacterial effect. By contrast, an array of graphene flakes grown perpendicularly to the surface by a plasma-enhanced CVD (PECVD) process prevent biofilm formation. Electron microscopy reveals that the exposed edges of vertically aligned graphene flakes penetrate the bacterial membrane and drain the cytosolic content. Bacteria are not able to develop resistance to this killing mechanism during multiple exposures. By keeping the height of the vertical graphene coating between 60 and 100 nm, the coating is able to effectively kill bacteria, while being completely harmless to mammalian cells.
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| 8. |
- Wang, Nan, 1988, et al.
(författare)
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Efficient surface modification of carbon nanotubes for fabricating high performance CNT based hybrid nanostructures
- 2017
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 111, s. 402-410
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotubes (CNTs) were chemically modified to achieve strong binding strength with the attached functional components as well as good dispersability and nanoparticle size-uniformity. An efficient multi-oxidation process was developed to create porous out layer with many nanoscale defects on the surface of CNTs for metallic nanoparticle close attachment and bond sufficient oxygen-containing groups, which assisted the dispersion of CNTs in the aqueous solution. The surface modified CNTs have advantages of strong binding capability, large surface area, high mechanical strength and good dispersability, which show great potential as building blocks for hybrid nanomaterials. Monodispersed silver nano particles with an average size of 3 nm were formed from inside the created nanoscale defects on the surface of CNTs without any obvious agglomerations. The fabricated hybrid exhibited much enhanced anti-bacterial performance compared to commercial silver nanoparticles due to the combined antibacterial effects of CNTs and silver nanoparticles. With these superior properties, the developed surface modification process could be widely used for improving the performances of many CNT based hybrid nanomaterials in diverse applications.
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