| 1. |
- Andersson, John, 1993, et al.
(författare)
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Polymer Brushes on Silica Nanostructures Prepared by Aminopropylsilatrane Click Chemistry: Superior Antifouling and Biofunctionality
- 2023
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 15:7, s. 10228-10239
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Tidskriftsartikel (refereegranskat)abstract
- In nanobiotechnology, the importance of controlling interactions between biological molecules and surfaces is paramount. In recent years, many devices based on nanostructured silicon materials have been presented, such as nanopores and nanochannels. However, there is still a clear lack of simple, reliable, and efficient protocols for preventing and controlling biomolecule adsorption in such structures. In this work, we show a simple method for passivation or selective biofunctionalization of silica, without the need for polymerization reactions or vapor-phase deposition. The surface is simply exposed stepwise to three different chemicals over the course of ∼1 h. First, the use of aminopropylsilatrane is used to create a monolayer of amines, yielding more uniform layers than conventional silanization protocols. Second, a cross-linker layer and click chemistry are used to make the surface reactive toward thiols. In the third step, thick and dense poly(ethylene glycol) brushes are prepared by a grafting-to approach. The modified surfaces are shown to be superior to existing options for silica modification, exhibiting ultralow fouling (a few ng/cm2) after exposure to crude serum. In addition, by including a fraction of biotinylated polymer end groups, the surface can be functionalized further. We show that avidin can be detected label-free from a serum solution with a selectivity (compared to nonspecific binding) of more than 98% without the need for a reference channel. Furthermore, we show that our method can passivate the interior of 150 nm × 100 nm nanochannels in silica, showing complete elimination of adsorption of a sticky fluorescent protein. Additionally, our method is shown to be compatible with modifications of solid-state nanopores in 20 nm thin silicon nitride membranes and reduces the noise in the ion current. We consider these findings highly important for the broad field of nanobiotechnology, and we believe that our method will be very useful for a great variety of surface-based sensors and analytical devices.
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| 2. |
- Forsvall, Andreas, et al.
(författare)
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Evaluation of the Forsvall biopsy needle in an ex vivo model of transrectal prostate biopsy - a novel needle design with the objective to reduce the risk of post-biopsy infection
- 2021
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Ingår i: Scandinavian Journal of Urology. - : Medical Journals Sweden AB. - 2168-1805 .- 2168-1813. ; 55:3, s. 227-234
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Tidskriftsartikel (refereegranskat)abstract
- Background Transrectal prostate biopsy (TRbx) transfers colonic bacteria into prostatic tissue, potentially causing infectious complications, including sepsis. Our objective was to determine whether biopsy needle shape, surface properties and sampling mechanism affect the number of bacteria transferred through the colon wall, and evaluate a novel needle with improved properties. Methods The standard Tru-Cut biopsy needle used today was evaluated for mechanisms of bacterial transfer in a pilot study. A novel Tru-Cut needle (Forsvall needle prototype) was developed. TRbx was simulated using human colons ex-vivo. Four subtypes of the prototype needle were compared with a standard Tru-Cut needle (BARD 18 G). Prototype and standard needles were used to puncture 4 different colon specimens in 10 randomized sites per colon. Needles were submerged into culture media to capture translocated bacteria. The media was cultured on blood agar and then the total amount of transferred bacteria was calculated for each needle. The primary outcome measure was the percent reduction of bacteria translocated by the prototype needles relative to the standard needle. Secondary outcome measures were the effects of tip design and coating on the percent reduction of translocated bacteria. Results Prototype needles reduced the number of translocated bacteria by, on average, 96.0% (95% confidence interval 93.0-97.7%; p < 0.001) relative to the standard needle. This percent reduction was not significantly affected by prototype needle tip style or surface coating. Conclusions The Forsvall needle significantly reduces colonic bacterial translocation, suggesting that it could reduce infectious complications in prostate biopsy. A clinical trial has been initiated.
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| 3. |
- Acimovic, Srdjan, 1982, et al.
(författare)
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Antibody−antigen interaction dynamics revealed by analysis of single-molecule equilibrium fluctuations on individual plasmonic nanoparticle biosensors
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 12:10, s. 9958-9965
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Tidskriftsartikel (refereegranskat)abstract
- Antibody−antigen interactions are complex events central to immune response, in vivo and in vitro diagnostics, and development of therapeutic substances. We developed an ultrastable single-molecule localized surface plasmon resonance (LSPR) sensing platform optimized for studying antibody−antigen interaction kinetics over very long time scales. The setup allowed us to perform equilibrium fluctuations analysis of the PEG/anti-PEG interaction. By time and frequency domain analysis, we demonstrate that reversible adsorption of monovalently bound anti-PEG antibodies is the dominant factor affecting the LSPR fluctuations. The results suggest that equilibrium fluctuation analysis can be an alternative to established methods for determination of interaction rates. In particular, the methodology is suited to analyze molecular systems whose properties change during the initial interaction phases, for example, due to mass transport limitations or, as demonstrated here, because the effective association rate constant varies with surface concentration of adsorbed molecules.
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| 4. |
- Acimovic, Srdjan, 1982, et al.
(författare)
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Superior LSPR substrates based on electromagnetic decoupling for on-a-chip high-throughput label-free biosensing
- 2017
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Ingår i: Light: Science and Applications. - : Springer Science and Business Media LLC. - 2047-7538 .- 2095-5545. ; 6:8, s. e17042-
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Tidskriftsartikel (refereegranskat)abstract
- Localized surface plasmon resonance (LSPR) biosensing based on supported metal nanoparticles offers unparalleled possibilities for high-end miniaturization, multiplexing and high-throughput label-free molecular interaction analysis in real time when integrated within an opto-fluidic environment. However, such LSPR-sensing devices typically contain extremely large regions of dielectric materials that are open to molecular adsorption, which must be carefully blocked to avoid compromising the device readings. To address this issue, we made the support essentially invisible to the LSPR by carefully removing the dielectric material overlapping with the localized plasmonic fields through optimized wet-etching. The resulting LSPR substrate, which consists of gold nanodisks centered on narrow SiO2 pillars, exhibits markedly reduced vulnerability to nonspecific substrate adsorption, thus allowing, in an ideal case, the implementation of thicker and more efficient passivation layers. We demonstrate that this approach is effective and fully compatible with state-of-the-art multiplexed real-time biosensing technology and thus represents the ideal substrate design for high-throughput label-free biosensing systems with minimal sample consumption.
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| 5. |
- Aludden, Hanna, 1984, et al.
(författare)
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Histological and radiological outcome after horizontal guided bone regeneration with bovine bone mineral alone or in combination with bone in edentulous atrophic maxilla: A randomized controlled trial
- 2024
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Ingår i: CLINICAL ORAL IMPLANTS RESEARCH. - : John Wiley & Sons. - 0905-7161 .- 1600-0501. ; 35:4, s. 396-406
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveTo assess the radiological and histological outcome after horizontal guided bone regeneration (GBR) with deproteinized bovine bone mineral (DBBM) alone or in combination with particulate autogenous bone (PAB).Materials and MethodsEighteen edentulous patients with an alveolar ridge of <= 4 mm were included in this split-mouth randomized controlled trial. Horizontal GBR with a graft composition of 100% DBBM (100:0) on one side and 90% DBBM and 10% PAB (90:10) on the other side were conducted in all patients. Cone beam computed tomography (CBCT) was obtained preoperatively, immediately postoperative, and after 10 months of healing. Width and volumetric changes in the alveolar process were measured on CBCT. Implants were placed after 10 months of graft healing where biopsies were obtained for histomorphometrical evaluation.ResultsThe gained widths were 4.9 (+/- 2.4) mm (100:0) and 4.5 (+/- 2.0) mm (90:10) at 3 mm from the top of the crest, and 5.6 (+/- 1.3) mm (100:0) and 4.6 (+/- 2.1) mm (90:10) at 6 mm from the top of the crest. The mean volumetric reductions were 32.8% (+/- 23.8) (100:0) and 38.2% (+/- 23.2) (90:10). Histomorphometry revealed that mean percentages of bone were 50.8% (+/- 10.7) (100:0) and 46.4% (+/- 11.3) (90:10), DBBM were 31.6% (+/- 12.6) (100:0) and 35.4% (+/- 14.8) (90:10), and non-mineralized tissue were 17.6% (+/- 11.7; 100:0) and 18.2% (+/- 18.2) (90:10). No significant differences were evident between in any evaluated parameters.ConclusionsThere were no additional effects of adding PAB to DBBM regarding bone formation, width changes, or volumetric changes after 10 months of graft healing.
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| 6. |
- Andersson, John, 1993, et al.
(författare)
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Control of Polymer Brush Morphology, Rheology, and Protein Repulsion by Hydrogen Bond Complexation
- 2021
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 37:16, s. 4943-4952
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Tidskriftsartikel (refereegranskat)abstract
- Polymer brushes are widely used to alter the properties of interfaces. In particular, poly(ethylene glycol) (PEG) and similar polymers can make surfaces inert toward biomolecular adsorption. Neutral hydrophilic brushes are normally considered to have static properties at a given temperature. As an example, PEG is not responsive to pH or ionic strength. Here we show that, by simply introducing a polymeric acid such as poly(methacrylic acid) (PMAA), the highly hydrated brush barrier can change its properties entirely. This is caused by multivalent hydrogen bonds in an extremely pH-sensitive process. Remarkably, it is sufficient to reduce the pH to 5 for complexation to occur at the interface, which is two units higher than in the corresponding bulk systems. Below this critical pH, PMAA starts to bind to PEG in large amounts (comparable to the PEG amount), causing the brush to gradually compact and dehydrate. The brush also undergoes major rheology changes, from viscoelastic to rigid. Furthermore, the protein repelling ability of PEG is lost after reaching a threshold in the amount of PMAA bound. The changes in brush properties are tunable and become more pronounced when more PMAA is bound. The initial brush state is fully recovered when releasing PMAA by returning to physiological pH. Our findings are relevant for many applications involving functional interfaces, such as capture-release of biomolecules.
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| 7. |
- Andersson, John, 1993, et al.
(författare)
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Pore performance: artificial nanoscale constructs that mimic the biomolecular transport of the nuclear pore complex
- 2022
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 4:23, s. 4925-4937
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Forskningsöversikt (refereegranskat)abstract
- The nuclear pore complex is a nanoscale assembly that achieves shuttle-cargo transport of biomolecules: a certain cargo molecule can only pass the barrier if it is attached to a shuttle molecule. In this review we summarize the most important efforts aiming to reproduce this feature in artificial settings. This can be achieved by solid state nanopores that have been functionalized with the most important proteins found in the biological system. Alternatively, the nanopores are chemically modified with synthetic polymers. However, only a few studies have demonstrated a shuttle-cargo transport mechanism and due to cargo leakage, the selectivity is not comparable to that of the biological system. Other recent approaches are based on DNA origami, though biomolecule transport has not yet been studied with these. The highest selectivity has been achieved with macroscopic gels, but they are yet to be scaled down to nano-dimensions. It is concluded that although several interesting studies exist, we are still far from achieving selective and efficient artificial shuttle-cargo transport of biomolecules. Besides being of fundamental interest, such a system could be potentially useful in bioanalytical devices.
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| 8. |
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| 9. |
- Andersson, John, 1993, et al.
(författare)
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Surface plasmon resonance sensing with thin films of palladium and platinum - quantitative and real-time analysis
- 2022
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 24:7, s. 4588-4594
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon resonance (SPR) is a highly useful technique in biology and is gradually becoming useful also for materials science. However, measurements to date have been performed almost exclusively on gold, which limits the possibility to probe chemical modifications of other metals. In this work we show that 20 nm Pd and Pt films work "fairly well" for quantitative SPR sensing of organic films despite the high light absorption. In the interval between total reflection and the SPR angle, high intensity changes occur when a film is formed on the surface. Fresnel models accurately describe the full angular spectra and our data analysis provides good resolution of surface coverage in air (a few ng cm(-2)). Overall, the Pd sensors behave quite similarly to 50 nm gold in terms of sensitivity and field extension, although the noise level in real-time measurements is similar to 5 times higher. The Pt sensors exhibit a longer extension of the evanescent field and similar to 10 times higher noise compared to gold. Yet, formation of organic layers a few nm in thickness can still be monitored in real-time. As a model system, we use thiolated poly(ethylene glycol) to make Pd and Pt protein repelling. Our findings show how SPR can be used for studying chemical modifications of two metals that are important in several contexts, for instance within heterogeneous catalysis. We emphasize the advantages of simple sample preparation and accurate quantitative analysis in the planar geometry by Fresnel models.
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| 10. |
- Bergström, Sara K., et al.
(författare)
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A simplified multidimensional approach for analysis of complex biological samples : on-line LC-CE-MS
- 2006
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 131:7, s. 791-798
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Tidskriftsartikel (refereegranskat)abstract
- Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL−1 (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.
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| 11. |
- Björkman, Anders, et al.
(författare)
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Cerebral reorganization in patients with brachial plexus birth injury and residual shoulder problems
- 2016
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Ingår i: Frontiers in Neurology. - : Frontiers Media SA. - 1664-2295. ; 7:DEC
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Tidskriftsartikel (refereegranskat)abstract
- The functional outcome after a brachial plexus birth injury (BPBI) is based on changes in the peripheral nerve and in the central nervous system. Most patients with a BPBI recover, but residual deficits in shoulder function are not uncommon. The aim of this study was to determine cerebral activation patterns in patients with BPBI and also residual symptoms from the shoulder. In seven patients (six females and one male, aged 17-23 years) with a BPBI and residual shoulder problems (Mallet score IV or lower), the cerebral response to active movement of the shoulder and elbow of the injured and healthy arm was monitored using functional magnetic resonance imaging at 3 T. Movements, i.e., shoulder rotation or elbow flexion and extension, of the injured side resulted in a more pronounced and more extended activation of the contralateral primary sensorimotor cortex compared to the activation seen after moving the healthy shoulder and elbow. In addition, moving the shoulder or elbow on the injured side resulted in increased activation in ipsilateral primary sensorimotor areas an also increased activation in associated sensorimotor areas, in both hemispheres, located further posterior in the parietal lobe, which are known to be important for integration of motor tasks and spatial aspects of motor control. Thus, in this preliminary study based on a small cohort, patients with BPBI and residual shoulder problems show reorganization in sensorimotor areas in both hemispheres of the brain. The increased activation in ipsilateral sensorimotor areas and in areas that deal with both integration of motor tasks and spatial aspects of motor control in both hemispheres indicates altered dynamics between the hemispheres, which may be a cerebral compensation for the injury.
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| 12. |
- Blake, Jolie, 1986, et al.
(författare)
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Scalable Reflective Plasmonic Structural Colors from Nanoparticles and Cavity Resonances – the Cyan-Magenta-Yellow Approach
- 2022
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 10:13
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic metasurfaces for color generation are emerging as important components for next generation display devices. Fabricating bright plasmonic colors economically and via easily scalable methods, however, remains difficult. Here, the authors demonstrate an efficient and scalable strategy based on colloidal lithography to fabricate silver-based reflective metal–insulator–nanodisk plasmonic cavities that provide a cyan-magenta-yellow (CMY) color palette with high relative luminance. With the same basic structure, they exploit different mechanisms to efficiently produce a complete subtractive color palette. Finite-difference time-domain simulations reveal that these mechanisms include gap surface plasmon modes for thin insulators and hybridized modes between disk plasmons and Fabry–Pérot modes for thicker systems. To produce yellow hues, they take advantage of higher-energy gap surface plasmon modes to allow resonance dips in the blue spectral region for comparably large nanodisks, thereby circumventing difficult fabrication of nanodisks less than 80 nm. It is anticipated that incorporation of these strategies can reduce fabrication constraints, produce bright saturated colors, and expedite large-scale production.
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| 13. |
- Brooke, Robert, 1989-, et al.
(författare)
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All-Printed Multilayers and Blends of Poly(dioxythiophene) Derivatives Patterned into Flexible Electrochromic Displays
- 2023
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Ingår i: Macromolecular materials and engineering. - : John Wiley and Sons Inc. - 1438-7492 .- 1439-2054. ; 308:2
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Tidskriftsartikel (refereegranskat)abstract
- Low-cost, flexible and thin display technology is becoming an interesting field of research as it can accompany the wide range of sensors being developed. Here, the synthesis of poly(dimethylpropylene-dioxythiophene) (PProDOT-Me2) by combining vapor phase polymerization and screen printing is presented. A multilayer architecture using poly(3,4-ethylenedioxythiophene) (PEDOT) and PProDOT-Me2 to allow for electrochromic switching of PProDOT-Me2, thereby eliminating the need for a supporting transparent conductive (metal oxide) layer is introduced. Furthermore, the technology is adapted to a blended architecture, which removes the additional processing steps and results in improved color contrast (∆E* > 25). This blend architecture is extended to other conductive polymers, such as PEDOT and polypyrrole (PPy), to highlight the ability of the technique to adjust the color of all-printed electrochromic displays. As a result, a green color is obtained when combining the blue and yellow states of PEDOT and PPy, respectively. This technology has the potential to pave the way for all-printed multicolored electrochromic displays for further utilization in printed electronic systems in various Internet of Things applications. © 2022 The Authors.
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| 14. |
- Chemnitz, Anette, et al.
(författare)
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Normalized activation in the somatosensory cortex 30 years following nerve repair in children- an fMRI study.
- 2015
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Ingår i: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 42:4, s. 2022-2027
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Tidskriftsartikel (refereegranskat)abstract
- The clinical outcome following a peripheral nerve injury in the upper extremity is generally better in young children than in teenagers and in adults, but the mechanism behind this difference is unknown. In twenty-eight patients with a complete median nerve injury sustained at the ages of 1-13 years (n=13) and 14-20 years (n=15), the cortical activation during tactile finger stimulation of the injured and healthy hands was monitored at a median time since injury of 28 years using functional magnetic resonance imaging (fMRI) at 3 Tesla. The results from the fMRI were compared with the clinical outcome and electroneurography. The cortical activation pattern following sensory stimulation of the median nerve innervated fingers was dependent on the patient's age at injury. Those injured at a young age (1-13 years) had an activation pattern similar to that of healthy controls. Furthermore, they showed a clinical outcome significantly superior (p=0.001) to the outcome in subjects injured at a later age, however, electroneurographical parameters did not differ between the groups. In subjects injured at age 14-20 years, a more extended activation of the contralateral hemisphere was seen in general. Interestingly, these patients also displayed changes in the ipsilateral hemisphere where a reduced inhibition of somatosensory areas was seen. This loss of ipsilateral inhibition correlated to increasing age at injury as well as to poor recovery of sensory functions in the hand. In conclusion, cerebral changes in both brain hemispheres may explain differences in clinical outcome following a median nerve injury in childhood or adolescence. This article is protected by copyright. All rights reserved.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Chu, Jiangtao, et al.
(författare)
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Fluorescence imaging of macromolecule transport in high molecular weight cut-off microdialysis
- 2014
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 406:29, s. 7601-7609
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Tidskriftsartikel (refereegranskat)abstract
- When microdialysis (MD) membrane exceeds molecular weight cut-off (MWCO) of 100 kDa, the fluid mechanics are in the ultrafiltration regime. Consequently, fluidic mass transport of macromolecules in the perfusate over the membrane may reduce the biological relevance of the sampling and cause an inflammatory response in the test subject. Therefore, a method to investigate the molecular transport of high MWCO MD is presented. An in vitro test chamber was fabricated to facilitate the fluorescent imaging of the MD sampling process, using fluoresceinylisothiocyanate (FITC) dextran and fluorescence microscopy. Qualitative studies on dextran behavior inside and outside the membrane were performed. Semiquantitative results showed clear dextran leakage from both 40 and 250 kDa dextran when 100 kDa MWCO membranes were used. Dextran 40 kDa leaked out with an order of magnitude higher concentration and the leakage pattern resembled more of a convective flow pattern compared with dextran 250 kDa, where the leakage pattern was more diffusion based. No leakage was observed when dextran 500 kDa was used as a colloid osmotic agent. The results in this study suggest that fluorescence imaging could be used as a method for qualitative and semiquantitative molecular transport and fluid dynamics studies of MD membranes and other hollow fiber catheter membranes.
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| 19. |
- Chu, Jiangtao, et al.
(författare)
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Impact of static pressure on transmembrane fluid exchange in high molecular weight cut off microdialysis
- 2014
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Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 16:2, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- With the interest of studying larger biomolecules by microdialysis (MD), this sampling technique has reached into the ultrafiltration region of fluid exchange, where fluid recovery (FR) has a strong dependence on pressure. Hence in this study, we focus on the fluid exchange across the high molecular weight cut off MD membrane under the influence of the static pressure in the sampling environment. A theoretical model is presented for MD with such membranes, where FR has a linear dependence upon the static pressure of the sample. Transmembrane (TM) osmotic pressure difference and MD perfusion rate decide how fast FR increases with increased static pressure.A test chamber for in vitro MD under static pressure was constructed and validated. It can hold four MD probes under controlled pressurized conditions. Comparison showed good agreement between experiment and theory. Moreover, test results showed that the fluid recovery of the test chamber MD can be set accurately via the chamber pressure, which is controlled by sample injection into the chamber at precise rate. This in vitro system is designed for modelling in vivo MD in cerebrospinal fluid and studies with biological samples in this system may be good models for in vivo MD.
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| 20. |
- Chu, Jiangtao, 1982-, et al.
(författare)
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Influence of different pluronic surface modifications and pressure on microdialysis protein extraction efficiency
- 2015
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Ingår i: Biomedical microdevices (Print). - Springer. - 1387-2176 .- 1572-8781.
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Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in using microdialysis (MD) for monitoring larger and more complexmolecules such as neuropeptides and proteins. This promotes the use of MD membranes withmolecular weight cut off (MWCO) of 100 kDa. Hence, the hydrodynamic property of themembrane goes to ultrafiltration, making the sampling more sensitive to pressure changes. Also,despite the large membrane pore size, studies have shown that membrane biofouling still leads tounstable catheter performance. Our objective is to study in vitro how four kinds of surfacemodifications (Pluronic L31, L44, F87 and F127+L31) affect the fluid recovery (FR) andextraction efficiency (EE) of 100 kDa MWCO MD catheters, under controlled pressure. Apressure chamber was employed to facilitate the tests, using as MD sample a protein standardwith proteins of similar concentrations as in human cerebral spinal fluid. The collected dialysatefractions were examined for FR and EE. Targeted mass spectrometry analysed the EE ofindividual proteins and peptides. The thicker the pluronic adsorption layer, the less thehydrodynamic diameter of the membrane pores, leading to lower and more stable FR. The foursurface modifications had three different behaviours: Pluronic F127 + L31 showed similarbehavior to the Pluronic F127 and the native original membrane; Pluronic F87 showed acontinuous EE increase with pressure; Pluronic L31 and L44 showed similar EE values, whichwere stable with pressure. Different surface modifications are clearly selective to differentproteins and peptides. We conclude that a pluronic surface modification could provide MDsampling with more stable FR, and more stable or enhanced EE with high FR, depending on theobjective of the sampling.
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| 21. |
- Chu, Jiangtao, 1982-, et al.
(författare)
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Influence of surface modification and static pressure on microdialysis protein extraction efficiency
- 2015
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Ingår i: Biomedical microdevices (Print). - Springer : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in using microdialysis (MD) for monitoring larger and more complexmolecules such as neuropeptides and proteins. This promotes the use of MD membranes withmolecular weight cut off (MWCO) of 100 kDa or above. The hydrodynamic property of themembrane goes to ultrafiltration or beyond, making the MD catheters more sensitive to pressure.In the meantime, despite the large pore size, studies have shown that membrane biofouling stilllead to unstable catheter performance. The objective is to study in vitro how 500 kDa dextranand Poloxamer 407 surface modification affect the fluid recovery (FR) and extraction efficiency(EE) of 100 kDa MWCO MD catheters. A pressure chamber was designed to facilitate the tests,using as MD sample a protein standard with similar concentrations as in human cerebral spinalfluid, comparing native and Poloxamer 407 modified MD catheters. The collected dialysatefractions were examined for FR and protein EE, employing Dot-it Spot-it Protein Assay for totalprotein EE and targeted mass spectrometry (MS) for EE of individual proteins and peptides. TheFR results suggested that the surface modified catheters were less sensitive to the pressure andprovide higher precision, and provided a FR closer to 100%. The surface modification did notshow a significant effect on the protein EE. The average total protein EE of surface modifiedcatheters was slightly higher than that of the native ones. The MS EE data of individual proteinsshowed a clear trend of complex response in EE with pressure.
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| 22. |
- Chu, Jiangtao, 1982-
(författare)
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Microdialysis Sampling of Macro Molecules : Fluid Characteristics, Extraction Efficiency and Enhanced Performance
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, fluid characteristics and sampling efficiency of high molecular weight cut-off microdialysis are presented, with the aim of improving the understanding of microdialysis sampling mechanisms and its performance regarding extraction efficiency of biological fluid and biomarkers.Microdialysis is a well-established clinical sampling tool for monitoring small biomarkers such as lactate and glucose. In recent years, interest has raised in using high molecular weight cut-off microdialysis to sample macro molecules such as neuropeptides, cytokines and proteins. However, with the increase of the membrane pore size, high molecular weight cut-off microdialysis exhibits drawbacks such like unstable catheter performance, imbalanced fluid recovery, low and unstable molecule extraction efficiency, etc. But still, the fluid characteristics of high molecular weight cut-off microdialysis is rarely studied, and the clinical or in vitro molecule sampling efficiency from recent studies vary from each other and are difficult to compare. Therefore, in this thesis three aspects of high molecular weight cut-off microdialysis have been explored. The first, the fluid characteristics of large pore microdialysis has been investigated, theoretically and experimentally. The results suggest that the experimental fluid recovery is in consistency with its theoretical formula. The second, the macromolecule transport behaviour has been visualized and semi-quantified, using an in vitro test system and fluorescence imaging. The third, two in vitro tests have been done to mimic in vivo cerebrospinal fluid sampling under pressurization, using native and differently surface modified catheters. As results, individual protein/peptide extraction efficiencies were achieved, using targeted mass spectrometry analysis.In summary, a theory system of the fluid characteristics of high molecular weight cut-off microdialysis has been built and testified; Macromolecular transport of microdialysis catheter has been visualized; In vivo biomolecules sampling has been simulated by well-defined in vitro studies; Individual biomolecular extraction efficiency has been shown; Different surface modifications of microdialysis catheter have been investigated. It was found that, improved sampling performance can be achieved, in terms of balanced fluid recovery and controlled protein extraction efficiency.
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| 23. |
- Chu, Jiangtao, 1982-, et al.
(författare)
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Protein Desalination Chip for Mass Spectrometry Sample Preparation
- 2015
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Konferensbidrag (refereegranskat)abstract
- This work focuses on desalination of a protein sample in a lab-on-chip device using the ion concentration polarization (ICP) technique. It was demonstrated with a salt containing buffer with four proteins and two peptides of concentrations typical to cerebrospinal fluid (CSF). Not only was the output desalinated but its protein concentration with large molecular weight (MW) was as much as 3 times higher for the largest protein compared to the original. We conclude that ICP based microfluidic chips have great potential for desalination and protein concentration in microdialysis sampling coupled to mass spectroscopy (MS).
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| 24. |
- Claudio, Virginia, 1985, et al.
(författare)
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Single-Particle Plasmon Sensing of Discrete Molecular Events: Binding Position versus Signal Variations for Different Sensor Geometries
- 2014
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:13, s. 6980-6988
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Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of a surface plasmon to the dielectric environment makes it a viable tool in detecting single molecules. To be able to precisely determine sensed molecular concentrations and carry out precise analyses of single-molecule binding/unbinding events in real time it is necessary to quantify rigorously the relation between the number of bound molecules and the spectral response of the plasmonic sensor. However, this is challenging as this relation is subject to an uncertainty which is highly dependent on the spatially varying response of the plasmonic nanosensor of choice. The origin of this uncertainty is little understood, and its effect is often disregarded in quantitative sensing experiments. Here, we employ stochastic diffusion-reaction simulations of biomolecular interactions on a sensor’s surface combined with electromagnetic calculations of the plasmon resonance peak shift of three metal nanosensors (disk, cone, dimer) to clarify the interplay between position-dependent binding probability and inhomogeneous sensitivity distribution in determining the statistical characteristics of the total signal upon molecular binding. This approach is generally applicable regardless of the specific transduction mechanism at the basis of sensing. Here we identify how this interplay affects the feasibility of using certain plasmonic sensors for sensing low concentrations or real-time monitoring of individual binding reactions and how illumination conditions may affect the level of uncertainty of the measured signal upon molecular binding.
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| 25. |
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| 26. |
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| 27. |
- Conca, Dario Valter, et al.
(författare)
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The role of membrane complexity in the early entry stages of SARS-CoV-2 variants
- 2023
-
Ingår i: European Biophysics Journal. - 1432-1017 .- 0175-7571. ; 52:SUPPL 1, s. S176-S176
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The highest density of mutations in SARS-CoV-2 variants is located on the spike glycoprotein (S), which is responsible for receptor ACE2 engagement. This suggests that SARS-CoV-2 is evolving to optimize viral entry. Several molecular studies report differences in the affinity between isolated S and ACE2 among variants. However, overall ACE2 affinity poorly correlates with the increased infectivity of recent variants. We address this discrepancy by considering the virus interaction with the whole plasma membrane and study the role of avidity and membrane complexity in modulating virus-host binding. To this end, we employ an in-vitro model system combining single-particle tracking and native supported lipid bilayers (nSLBs) made from lung epithelial cells. As virion mimics, we developed S-decorated liposomes that allow for direct comparison between variants and BSL-1 handling. Sliposome interaction with nSLBs showed a significant increase in avidity for Omicron compared to Delta and Wuhan strains. Further, using single-molecule force spectroscopy, we reveal a higher affinity for Omicron and Delta S to sensor immobilise heparan sulfate (HS). Our results indicate a shift in the variants’ attachment strategy towards more efficient use of coreceptors and the role of HS as an initial docking site that facilitates virus accumulation at the membrane and ACE2 engagement.
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| 28. |
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| 29. |
- Dahlin, Andreas, 1980
(författare)
-
Biochemical Sensing with Nanoplasmonic Architectures: We Know How but Do We Know Why?
- 2021
-
Ingår i: Annual Review of Analytical Chemistry. - : Annual Reviews. - 1936-1327 .- 1936-1335. ; 14, s. 281-297
-
Forskningsöversikt (refereegranskat)abstract
- Here, the research field of nanoplasmonic sensors is placed under scrutiny, with focus on affinity-based detection using refractive index changes. This review describes how nanostructured plasmonic sensors can deliver unique advantages compared to the established surface plasmon resonance technique, where a planar metal surface is used. At the same time, it shows that these features are actually only useful in quite specific situations. Recent trends in the field are also discussed and some devices that claim extraordinary performance are questioned. It is argued that the most important challenges are related to limited receptor affinity and nonspecific binding rather than instrumental performance. Although some nanoplasmonic sensors may be useful in certain situations, it seems likely that conventional surface plasmon resonance will continue to dominate biomolecular interaction analysis. For detection of analytes in complex samples, plasmonics may be an important tool, but probably not in the form of direct refractometric detection.
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| 30. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Electrochemical plasmonic sensors
- 2012
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 402:5, s. 1773-1784
-
Forskningsöversikt (refereegranskat)abstract
- The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.
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| 31. |
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| 32. |
- Dahlin, Andreas, 1980, et al.
(författare)
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High-Resolution Microspectroscopy of Plasmonic Nanostructures for Miniaturized Biosensing
- 2009
-
Ingår i: Analytical Chemistry. - : American Chemical Society. - 0003-2700 .- 1520-6882. ; 81:16, s. 6572-6580
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we demonstrate how to perform microscale spectroscopy of plasmonic nanostructures in order to minimize the noise when determining the resonance peak wavelength. This is accomplished using an experimental setup containing standard optical components mounted on an ordinary light microscope. We present a detailed comparison between extinction spectroscopy in transmission mode and scattering spectroscopy under dark field illumination, which shows that extinction measurements provide higher signal-to-noise in almost all situations. Furthermore, it is shown that rational selection of nanostructure, hardware components, and data analysis algorithms enables tracking of the particle plasmon resonance wavelength from a 10 mu m x 50 mu m area with a resolution of 10(-3) nm in transmission mode. We investigate how the temporal resolution, which can be improved down to 17 Ins, affects, the noise characteristics. In addition, we show how data can be acquired from an area as small as 2 mu m x 10 mu m (similar to 240 particles) at the expense of higher noise on longer time scales. In comparison with previous work on macroscopic sensor designs, this represents a sensor miniaturization of 5 orders of magnitude, without any loss in signal-to-noise performance. As a model system, we illustrate biomolecular detection using gold nanodisks prepared by colloidal lithography. The microextinction measurements of nanodisks described here provide detection of protein surface coverages as low as 40 pg/cm(2) (less than0.1% of saturated binding). In fact, the miniaturized system provides a detection limit in terms of surface coverage comparable to state of the art macroscopic sensors, while simultaneously being as close to single protein molecule detection as sensors based on a single nanoparticle.
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| 33. |
- Dahlin, Andreas, et al.
(författare)
-
Improving the instrumental resolution of sensors based on localized surface plasmon resonance
- 2006
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 78:13, s. 4416-4423
-
Tidskriftsartikel (refereegranskat)abstract
- The colorimetric variations induced upon changes in interfacial refractive index of nanoscale noble metal structures exhibiting localized surface plasmon resonance (LSPR) provides a convenient means of label-free, affinity-based detection of biomolecular recognition reactions. However, despite being similar in nature to conventional SPR, LSPR has so far suffered from significantly lower data quality in terms of its signal-to-noise ratio (S/N) in typical biomolecular recognition analysis. In this work, generic data analysis algorithms and a simple experimental setup that provide a S/N upon protein binding that is comparable to that of state-of-the art SPR systems are presented. Specifically, it is demonstrated how temporal variations ( rate similar to 0.5 Hz) in parameters proportional to the resonance peak position can be recorded simultaneously, yielding a peak position precision of < 5 x 10(-4) nm and an extinction noise level of < 5 x 10(-6) absorbance units (Abs). This, in turn, is shown to provide a S/N of similar to 2000 ( equivalent to a detection limit of < 0.1 ng/cm(2)) for typical protein binding reactions. Furthermore, the importance of utilizing changes in both peak position and magnitude is highlighted by comparing different LSPR active noble metal architectures that respond differently to bulk and interfacial refractive index changes.
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| 34. |
- Dahlin, Andreas, et al.
(författare)
-
Localized Surface Plasmon Resonance Sensing of Lipid-Membrane-Mediated Biorecognition Events
- 2005
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:14, s. 5043-5048
-
Tidskriftsartikel (refereegranskat)abstract
- Supported phospholipid bilayers (SPBs) have emerged as important model systems for studies of the natural cell membrane and its components, which are essential for the integrity and function of cells in all living organisms, and also constitute common targets for therapeutic drugs and in disease diagnosis. However, the preferential occurrence of spontaneous SPB formation on silicon-based substrates, but not on bare noble-metal surfaces, has so far excluded the use of the localized surface plasmon resonance (LSPR) sensing principle for studies of lipid-membrane-mediated biorecognition reactions. This is because the LSPR phenomenon is associated with, and strongly confined to, the interfacial region of nanometric noble-metal particles. This problem has been overcome in this study by a self-assembly process utilizing localized rupture of phospholipid vesicles on silicon dioxide in the bottom of nanometric holes in a thin gold film. The hole-induced localization of the LSPR field to the voids of the holes is demonstrated to provide an extension of the LSPR sensing concept to studies of reactions confined exclusively to SPB-patches supported on SiO2. In particular, we emphasize the possibility of performing label-free studies of lipid-membrane-mediated reaction kinetics, including the compatibility of the assay with array-based reading (similar to 7 x 7 mu m(2)) and detection of signals originating from bound protein in the zeptomole regime.
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| 35. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Localized surface plasmon sensing of lipid-membrane-mediated biorecognition events
- 2005
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:14, s. 5043-5048
-
Tidskriftsartikel (refereegranskat)abstract
- Supported phospholipid bilayers (SPBs) have emerged as important model systems for studies of the natural cell membrane and its components, which are essential for the integrity and function of cells in all living organisms, and also constitute common targets for therapeutic drugs and in disease diagnosis. However, the preferential occurrence of spontaneous SPB formation on silicon-based substrates, but not on bare noble-metal surfaces, has so far excluded the use of the localized surface plasmon resonance (LSPR) sensing principle for studies of lipid-membrane-mediated biorecognition reactions. This is because the LSPR phenomenon is associated with, and strongly confined to, the interfacial region of nanometric noble-metal particles. This problem has been overcome in this study by a self-assembly process utilizing localized rupture of phospholipid vesicles on silicon dioxide in the bottom of nanometric holes in a thin gold film. The hole-induced localization of the LSPR field to the voids of the holes is demonstrated to provide an extension of the LSPR sensing concept to studies of reactions confined exclusively to SPB-patches supported on SiO2. In particular, we emphasize the possibility of performing label-free studies of lipid-membrane-mediated reaction kinetics, including the compatibility of the assay with array-based reading (similar to 7 x 7 mu m(2)) and detection of signals originating from bound protein in the zeptomole regime.
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| 36. |
- Dahlin, Andreas, 1976-
(författare)
-
Microscale Tools for Sample Preparation, Separation and Detection of Neuropeptides
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The analysis of low abundant biological molecules is often challenging due to their chemical properties, low concentration and limited sample volumes. Neuropeptides are one group of molecules that fits these criteria. Neuropeptides also play an important role in biological functions, which makes them extra interesting to analyze. A classic chemical analysis involves sampling, sample preparation, separation and detection. In this thesis, an enhanced solid supported microdialysis method was developed and used as a combined sampling- and preparation technique. In general, significantly increased extraction efficiency was obtained for all studied peptides. To be able to control the small sample volumes and to minimize the loss of neuropeptides because of unwanted adsorption onto surfaces, the subsequent analysis steps were miniaturized to a micro total analysis system (µ-TAS), which allowed sample pre-treatment, injection, separation, manipulation and detection. In order to incorporate these analysis functions to a microchip, a novel microfabrication protocol was developed. This method facilitated three-dimensional structures to be fabricated without the need of clean room facilities. The sample pre-treatment step was carried out by solid phase extraction from beads packed in the microchip. Femtomole levels of neuropeptides were detected from samples possessing the same properties as microdialysates. The developed injection system made it possible to conduct injections from a liquid chromatographic separation into a capillary electrophoresis channel, which facilitated for advanced multidimensional separations. An electrochemical sample manipulation system was also developed. In the last part, different electrospray emitter tip designs made directly from the edge of the microchip substrate were developed and evaluated. The emitters were proven to be comparable with conventional, capillary based emitters in stability, durability and dynamic flow range. Although additional developments remain, the analysis steps described in this thesis open a door to an integrated, on-line µ-TAS for neuropeptides analysis in complex biological samples.
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| 37. |
- Dahlin, Andreas, 1980
(författare)
-
Nanoplasmonic Biosensors compatible with Artificial Cell Membranes
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within life science, there is currently an intense search for novel techniques that enable efficient and reliable analysis of biomolecular interactions. Such methods have future applications within medical diagnostics and drug development, as well as within proteomic research in general. Lately, several concepts have emerged that are based on monitoring molecular binding to surfaces via optical, mechanical or electrical signal transduction. In particular, the plasmons associated with metallic nanoparticles are of interest since they offer a convenient way to monitor biomolecular interactions, also in a miniaturized format, by optical spectroscopy.This thesis describes the development of a biosensor based on the optical properties of nanoscale apertures in continuous metal films. The fabrication and characterization of the nanostructure is described, as well as surface modification protocols based on thiol chemistry for material-specific functionalization. In addition, an experimental setup for spectroscopy is presented together with data analysis algorithms for minimizing noise.It is emphasized that, from an experimental sensing perspective, nanoholes and nanoparticles have essentially the same plasmonic properties. However, the nanoholes offer several advantages because of the fact that the structure is physically different. In particular, it is shown how various artificial cell membranes can be spontaneously formed inside nanoholes. This makes the sensor compatible with studies of processes related to biological membranes. In this context, membrane-bound proteins are of special interest since they constitute a third of our genome and represent the target of half of the most common medical drugs. Potential future applications of the artificial membranes on the plasmonic nanostructures are discussed, with focus on probing transport across the membrane.
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| 38. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Nanoplasmonic sensing of metal-halide complex formation and the electric double layer capacitor
- 2012
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 4:7, s. 2339-2351
-
Tidskriftsartikel (refereegranskat)abstract
- Many nanotechnological devices are based on implementing electrochemistry with plasmonic nanostructures, but these systems are challenging to understand. We present a detailed study of the influence of electrochemical potentials on plasmon resonances, in the absence of surface coatings and redox active molecules, by synchronized voltammetry and spectroscopy. The experiments are performed on gold nanodisks and nanohole arrays in thin gold films, which are fabricated by improved methods. New insights are provided by high resolution spectroscopy and variable scan rates. Furthermore, we introduce new analytical models in order to understand the spectral changes quantitatively. In contrast to most previous literature, we find that the plasmonic signal is caused almost entirely by the formation of ionic complexes on the metal surface, most likely gold chloride in this study. The refractometric sensing effect from the ions in the electric double layer can be fully neglected, and the charging of the metal gives a surprisingly small effect for these systems. Our conclusions are consistent for both localized nanoparticle plasmons and propagating surface plasmons. We consider the results in this work especially important in the context of combined electrochemical and optical sensors.
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| 39. |
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| 40. |
- Dahlin, Andreas P., et al.
(författare)
-
Methodological aspects on microdialysis protein sampling and quantification in biological fluids : an in vitro study on human ventricular CSF.
- 2010
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:11, s. 4376-4385
-
Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in sampling of protein biomarkers from the interstitial compartment of the brain and other organs using high molecular cutoff membrane microdialysis (MD) catheters. However, recent data suggest that protein sampling across such MD membranes is a highly complex process that needs to be further studied. Here, we report three major improvements for microdialysis sampling of proteins in complex biological matrixes. The improvements in this in vitro study using human ventricular cerebrospinal fluid as the sample matrix include increased fluid recovery control, decreased protein adsorption on the microdialysis membrane and materials, and novel quantitative mass spectrometry analysis. Dextrans in different concentrations and sizes were added to the perfusion fluid. It was found that dextrans with molecular mass 250 and 500 kDa provided a fluid recovery close to 100%. An improved fluid recovery precision could be obtained by self-assembly triblock polymer surface modification of the MD catheters. The modified catheters also delivered a significantly increased extraction efficiency for some of the investigated proteins. The final improvement was to analyze the dialysates with isobaric tagged (iTRAQ) proteomics, followed by tandem mass spectrometric analysis. By using this technique, 48 proteins could be quantified and analyzed with respect to their extraction efficiencies. The novel aspects of microdialysis protein sampling, detection, and quantification in biological fluids presented in this study should be considered as a first step toward better understanding and handling of the challenges associated with microdialysis sampling of proteins. The next step is to optimize the developed methodology in vivo.
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| 41. |
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| 42. |
- Dahlin, Andreas P, et al.
(författare)
-
Multiplexed quantification of proteins adsorbed to surface-modified and non-modified microdialysis membranes
- 2012
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 402:6, s. 2057-2067
-
Tidskriftsartikel (refereegranskat)abstract
- A simple and straightforward method for discovery and quantification of proteins adsorbed onto delicate and sensitive membrane surfaces is presented. The adsorbed proteins were enzymatically cleaved while still adsorbed onto the membranes using an on-surface enzymatic digestion (oSED). This was followed by isobaric tagging, nanoliquid chromatography, and tandem mass spectrometry. Protein adsorption on tri-block copolymer Poloxamer 407 surface-modified microdialysis (MD) membranes were compared with protein adsorption on unmodified MD membranes. Ventricular cerebrospinal fluid (vCSF) kept at 37 °C was used as sample matrix. In total, 19 proteins were quantified in two biological replicates. The surface-modified membranes adsorbed 33% less proteins than control membranes and the most abundant proteins were subunits of hemoglobin and clusterin. The adsorption of clusterin on the modified membranes was on average 36% compared to control membranes. The most common protein in vCSF, Albumin, was not identified adsorbed to the surface at all. It was also experimentally verified that oSED, in conjunction with tandem mass spectrometry can be used to quantify femtomole amounts of proteins adsorbed on limited and delicate surfaces, such as MD membranes. The method has great potential and can be used to study much more complex protein adsorption systems than previously reported.
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| 43. |
- Dahlin, Andreas P., et al.
(författare)
-
Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip
- 2005
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:16, s. 5356-5363
-
Tidskriftsartikel (refereegranskat)abstract
- A microchip in poly(dimethylsiloxane) (PDMS) for in-line solid-phase extraction-capillary electrophoresis-electrospray ionization-time-of-flight mass spectrometry (SPE-CE-ESI-TOF-MS) has been developed and evaluated. The chip was fabricated in a novel one-step procedure where mixed PDMS was cast over steel wires in a mold. The removed wires defined 50-um cylindrical channels. Fused-silica capillaries were inserted into the structure in a tight fit connection. The inner walls of the inserted fused-silica capillaries and the PDMS microchip channels were modified with a positively charged polymer, PolyE-323. The chip was fabricated in a two-level cross design. The channel at the lower level was packed with 5-um hyper-cross-linked polystyrene beads acting as a SPE medium used for desalting. The upper level channel acted as a CE channel and ended in an integrated emitter tip coated with conducting graphite powder to facilitate the electrical contact for sheathless ESI. An overpressure continuously provided fresh CE electrolyte independently of the flows in the different levels. Further studies were carried out in order to investigate the electrophoretic and flow rate properties of the chip. Finally, six-peptide mixtures, in different concentrations, dissolved in physiological salt solution was injected, desalted, separated, and sprayed into the mass spectrometer for analysis with a limit of detection in femtomole levels.
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| 44. |
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| 45. |
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| 46. |
- Dahlin, Andreas P, et al.
(författare)
-
Refined microdialysis method for protein biomarker sampling in acute brain injury in the neurointensive care setting
- 2014
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 86:17, s. 8671-8679
-
Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in cerebral microdialysis (MD) for sampling of protein biomarkers in neurointensive care (NIC) patients. Published data point to inherent problems with this methodology including protein interaction and biofouling leading to unstable catheter performance. This study tested the in vivo performance of a refined MD method including catheter surface modification, for protein biomarker sampling in a clinically relevant porcine brain injury model. Seven pigs of both sexes (10-12 weeks old; 22.2-27.3 kg) were included. Mean arterial blood pressure, heart rate, intracranial pressure (ICP) and cerebral perfusion pressure was recorded during the stepwise elevation of intracranial pressure by inflation of an epidural balloon catheter with saline (1 mL/20 min) until brain death. One naïve MD catheter and one surface modified with Pluronic F-127 (10 mm membrane, 100 kDa molecular weight cutoff MD catheter) were inserted into the right frontal cortex and perfused with mock CSF with 3% Dextran 500 at a flow rate of 1.0 μL/min and 20 min sample collection. Naïve catheters showed unstable fluid recovery, sensitive to ICP changes, which was significantly stabilized by surface modification. Three of seven naïve catheters failed to deliver a stable fluid recovery. MD levels of glucose, lactate, pyruvate, glutamate, glycerol and urea measured enzymatically showed an expected gradual ischemic and cellular distress response to the intervention without differences between naïve and surface modified catheters. The 17 most common proteins quantified by iTRAQ and nanoflow LC-MS/MS were used as biomarker models. These proteins showed a significantly more homogeneous response to the ICP intervention in surface modified compared to naïve MD catheters with improved extraction efficiency for most of the proteins. The refined MD method appears to improve the accuracy and precision of protein biomarker sampling in the NIC setting.
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| 47. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Performance of nanoplasmonic biosensors
- 2012
-
Ingår i: Nanoplasmonic Sensors. - New York, NY : Springer New York. - 9781461439332 ; , s. 231-264
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter aims to give an overview of how to optimize the performance of nanoplasmonic sensors. Specific biosensing challenges beyond the capability of current nanoplasmonic sensors will be discussed. Various methods to improve sensor performance will then be introduced, including solving issues related to surface chemistry. We distinguish the concept of signal enhancement, which is related to the choice of nanostructure and surface functionalization, from the concept of noise minimization, which is related to the spectroscopy techniques employed. The concepts of bulk sensitivity, figure of merit, nanostructure performance, and their relation to detection limit are discussed in detail.
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| 48. |
- Dahlin, Andreas, 1980
(författare)
-
Plasmonic biosensors: An integrated view of refractometric detection
- 2011
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- The book presents an integrated view of plasmonic biosensors that operate by refractometric detection. This means that analyte binding to the sensor surface induces a local change in refractive index, which alters the far field spectrum, as detected by optical spectroscopy. Other plasmonic biosensors such as those based on coupling between suspended nanoparticles or surface enhanced Raman scattering are not discussed in detail. All aspects of refractometric detection are considered in an integrated view. It is described how efficient surface functionalization becomes critical for specificity in order to reduce nonspecific interactions while preserving high affinity for the analyte. It is also shown how the influence from binding kinetics and mass transport limitations severely affects the applicability of these types of sensors. Some basic optics related to plasmonics is introduced. Nanoparticle plasmons and surface plasmons are described in depth. Plasmons in nanohole arrays as well as near field optics of plasmonic nanostructures are also presented. Throughout the book, analytical formula are given, although no expression is explicitly derived. It is emphasized under which assumptions the formulas hold and their validity is discussed. Numerical methods for plasmonics are not described in detail. Later chapters discuss experimental plasmon spectroscopy and spectral analysis, including the challenge of quantitative interpretation of the response. In particular, it is shown that the refractometric sensing performance of a plasmonic nanostructure is best evaluated in terms of relative intensity changes with liquid refractive index. The extension of the sensitivity into the liquid environment is shown to be another critical factor. Towards the end of the book, the theoretical framework is combined into an integrated view of sensor performance. Among other conclusions, it is suggested that novel nanoplasmonic sensors offer very few advatanges over the established methodology of surface plasmon resonance biosensing. As a final outlook, examples of combinations of plasmonic biosensors with other signal transduction mechanisms are presented.
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| 49. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Plasmonic Nanopores in Metal-Insulator-Metal Films
- 2014
-
Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 2:6, s. 556-564
-
Tidskriftsartikel (refereegranskat)abstract
- A novel type of plasmonic nanopore array in a metal-insulator-metal thin film is presented. The optical properties of this structure are described using a generic theoretical framework for surface waves in a coupled multilayer system. The characteristic spacing (short-range order) of the pores enables grating-type coupling to hybridized surface plasmons, with stronger coupling to some modes than others. The nature of the optical resonances and their excitation mechanisms can be conceptually understood from a charge distribution argument. The experimental results are further verified by numerical simulations, which also enable visualization of the near field. This study illustrates the surface plasmon characteristics (sensitive to periodicity) of the extinction maximum in the asymmetric spectral resonance induced by aperture arrays, while the transmission maximum corresponds to a resonance of localized character (sensitive to pore shape). Finally, the use of these nanopores for sensing applications through changes in the refractive index is evaluated.
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| 50. |
- Dahlin, Andreas, 1980, et al.
(författare)
-
Promises and challenges of nanoplasmonic devices for refractometric biosensing
- 2013
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Ingår i: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614 .- 2192-8606. ; 2:2, s. 83-101
-
Tidskriftsartikel (refereegranskat)abstract
- Optical biosensors based on surface plasmon resonance (SPR) in metallic thin films are currently standard tools for measuring molecular binding kinetics and affinities - an important task for biophysical studies and pharmaceutical development. Motivated by recent progress in the design and fabrication of metallic nanostructures, such as nanoparticles or nanoholes of various shapes, researchers have been pursuing a new generation of biosensors harnessing tailored plasmonic effects in these engineered nanostructures. Nanoplasmonic devices, while demanding nanofabrication, offer tunability with respect to sensor dimension and physical properties, thereby enabling novel biological interfacing opportunities and extreme miniaturization. Here we provide an integrated overview of refractometric biosensing with nanoplasmonic devices and highlight some recent examples of nanoplasmonic sensors capable of unique functions that are difficult to accomplish with conventional SPR. For example, since the local field strength and spatial distribution can be readily tuned by varying the shape and arrangement of nanostructures, biomolecular interactions can be controlled to occur in regions of high field strength. This may improve signal-to-noise and also enable sensing a small number of molecules. Furthermore, the nanoscale plasmonic sensor elements may, in combination with nanofabrication and materials-selective surface-modifications, make it possible to merge affinity biosensing with nanofluidic liquid handling.
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