| 1. |
- Cho, N. J., et al.
(författare)
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Alpha-Helical Peptide-Induced Vesicle Rupture Revealing New Insight into the Vesicle Fusion Process As Monitored in Situ by Quartz Crystal Microbalance-Dissipation and Reflectometry
- 2009
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 81:12, s. 4752-4761
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Tidskriftsartikel (refereegranskat)abstract
- We have used simultaneous quartz crystal microbalance-dissipation (QCM-D) monitoring and four-detector optical reflectometry to monitor in situ the structural transformation of intact vesicles to a lipid bilayer on a gold surface. The structural transformation of lipid vesicles to a bilayer was achieved by introducing a particular amphiphathic, a-helical (AH) peptide. The combined experimental apparatus allows us to simultaneously follow the acoustic and optical property, changes of the vesicle rupturing process upon interaction with AH peptides. While QCM-D and reflectometry have similar sensitivities in terms of mass and thickness resolution, there are unique advantages in operating these techniques simultaneously on the same substrate. These advantages permit us to (1) follow the complex interaction between AH peptides and intact vesicles with both acoustic and optical mass measurements, (2) calculate the amount of dynamically coupled water during the interaction between AH peptides and intact vesicles, (3) demonstrate that the unexpectedly large increase of both adsorbed mass and the film's energy dissipation is mainly caused by swelling of the vesicles during the binding interaction with AH peptides, and (4) permit us to understand the structural transformation from intact vesicles to a bilayer via the AH peptide interaction by monitoring viscoelastic properties, acoustic mass, optical mass, and thickness changes of both the binding and destabilization processes. From the deduced "hydration signature" we followed the complex transformation of lipid assemblies. On the basis of this information, a mechanism of this structural transformation is proposed that provides new insight into the process of vesicle fusion on solid substrates.
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| 2. |
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| 3. |
- Mazzotta, Francesco, 1985, et al.
(författare)
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Nanoplasmonic biosensing with on-chip electrical detection
- 2010
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Ingår i: Biosensors and Bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 26:4, s. 1131-1136
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Konferensbidrag (refereegranskat)abstract
- A nanoplasmonic biosensor chip with integrated electrical detection is presented. The concept is based on the local refractive index sensitivity of nanoplasmonic gold nanodisks (110 nm in diameter and 20 nm in height) that are fabricated, through a parallel method, directly on an array of silicon solar cells or photoactive diodes. The nanoplasmonic properties of the sensor chip were investigated both optically and electrically, with excellent agreement between the two. We show that local changes in the refractive index of the surrounding environment gives changes in the nanoplasmonic properties of the gold nanodisks, which induce corresponding changes in the photocurrent at single wavelengths of the nanoplasmonic solar cells. With a simple light-emitting diode as light source, and together with a material-specific modification protocol, the photocurrent output of the nanoplasmonic sensor chip was successfully used to monitor a specific biorecognition reaction in real-time.
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| 4. |
- Satriano, Cristina, et al.
(författare)
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Plasma oxidized polyhydroxymethylsiloxane – a new smooth surface for supported lipid bilayer formation
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:8, s. 5715-5725
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Tidskriftsartikel (refereegranskat)abstract
- A novel substrate For preparation of supported lipid bilayers (SLBs), smooth at the subnanometer scale and of variable thickness from ten to several hundred nanometers, was developed by surface oxidation at spin-coated poly(hydroxymethylsiloxane) (PHMS) films. The deposited polymeric thin films were modified by a combination of oxygen plasma and thermal treatment (PHMS(ox)), in order to convert the outermost surface layer of the polymer film to a stable SiO(2) film, suitable for SLB formation. The hydrophilic, SiO(2)-like surfaces were characterized by XPS, wetting angle, ellipsometry, and AFM. Lipid bilayers were formed on this surface using the well-known vesicle adsorption-rupture-fusion process, usually performed on glass or vapor-deposited SiO(2). Reproducible formation of homogeneous SLBs of different compositions (POPC. DOEPC. and POPC/DOPS) was demonstrated on the new SiO(2) surface by quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (S PR), and optical reflectometry measurements. The SLB formation kinetics on the PHMS(ox)-coated sensors showed very similar characteristics, for all investigated PHMS thicknesses, as on reference sensors coated with vapor-deposited SiO(2). The good adhesive properties of the PHMS to gold allows for the preparation of thin PHMS(ox) layers compatible with SPR. The much smaller roughness at the nanometer scale of the PHMS(ox) surfaces, compared to standard vapor-deposited SiO(2)-coated sensors, makes them advantageous for AFM and optical experiments and promising for patterning. To benefit optical experiments with the PHMS(ox) surfaces, it was also investigated how the PHMS film thickness influences the SPR and reflectometry responses upon SLB formation.
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| 5. |
- Wang, Guoliang, 1965-
(författare)
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Gas Sensing Based on Ellipsometric Readout : Methodology and Development
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The concept of an ellipsometric sensor array system - "an optical nose" - is presented. The system is used to monitor and discriminate gases. The optical readout is based on polarizer-compensator-sample-analyzer (PCSA) off-null ellipsometry. Thin porous silicon sensing layers with and without surface chemical modifications are used to measure low concentration methanol, ethanol and 2-propanol gases. The main contents of the thesis are:- Principle and construction of a prototype PCSA ellipsometric gas sensor system.- Optimization of the azimuth angle settings of the optical components in PCSA off-null ellipsometry to obtain the maximum readout sensitivity.- Application of return-path off-null ellipsometry in gas sensing as an alternative way to construct ellipsometric gas sensors.- Modification of porous silicon sensing layers by copper deposition to obtain different gas sensitivity for the enhancement of selectivity.- Multi-sensing concept of the optical nose to detect and discriminate alcohols using porous silicon sensing layers and pattern recognition techniques.So far, a prototype PCSA ellipsometric gas sensor system has been constructed and tested. Low concentration methanol, ethanol and 2-propanol vapors are detected and discriminated based on the PCSA off-null ellipsometric gas sensor system and porous silicon sensing layers.
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| 6. |
- Wang, Guoliang, 1965-, et al.
(författare)
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Return-path ellipsometry in gas sensing
- 2003
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 15, s. 216-220
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Tidskriftsartikel (refereegranskat)
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