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| 2. |
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| 3. |
- Beech, Jason P., et al.
(author)
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Capillary driven separation on patterned surfaces
- 2009
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In: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 785-787
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Conference paper (peer-reviewed)abstract
- Deterministic lateral displacement (DLD) is a powerful bimodal separation scheme [1] based on fluid flow through regular obstacle arrays that in its basic embodiment sends suspended particles in two different directions as a function of size. We show that without the need to seal devices and without the need for fluidic connections or pumps, particle separation can be achieved by the passive flow of a sample over a patterned surface. Risk of clogging is minimized by the movement of large particles above the obstacle array. Suitable application areas include blood fractionation and analysis of drinking water. 0
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| 4. |
- Beech, Jason P., et al.
(author)
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Gravitationally driven deterministic lateral displacement devices
- 2009
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In: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 779-781
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Conference paper (peer-reviewed)abstract
- Deterministic lateral displacement (DLD) is a powerful bimodal separation scheme [1] based on regular obstacle arrays that in its basic embodiment sends particles in two different directions as a function of size. We add functionality to the technique by including gravitational forces, as a perturbation to particles transported by fluid flow, and as a way of transporting the particles through a stationary fluid.
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| 5. |
- Beech, Jason P., et al.
(author)
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Shape-based particle sorting - A new paradigm in microfluidics
- 2009
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In: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 800-802
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Conference paper (peer-reviewed)abstract
- Conventional fractionation techniques fail to fully benefit from the variety in morphology and shape that is found among biological particles. Although light scattering in conventional FACS gives some information on the size and morphology of a particle, it is generally not capable of giving a definite number on specified dimensions of a small object. We demonstrate an approach where we select which dimension of a particular object is used to determine its trajectory through an obstacle course and thereby sort not merely with respect to hydrodynamic radius but rather with respect to e.g. thickness, length or width.
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| 6. |
- Beech, Jason P., et al.
(author)
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Throughput through thin-film fluidics
- 2008
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In: ; , s. 1492-1494
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Conference paper (peer-reviewed)abstract
- We demonstrate fluidics realized in thin film plastic foils patterned using roll-toroll nanoimprinting lithography (rrNIL). Realizing fluidics devices in thin plastic foils opens up for parallel operation in stacked devices. It also provides a convenient format for storage and distribution of the devices.
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| 7. |
- Beech, Jason P., et al.
(author)
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Tipping the balance with dielectrophoretic forces - An electric deterministic lateral displacement device
- 2008
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In: ; , s. 95-97
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Conference paper (peer-reviewed)abstract
- We present experimental results and simulations on a simple method for tunable particle separation based on a combination of Deterministic Lateral Displacement (DLD) and Insulator Based Dielectrophoresis (I-DEP). Rather than deriving its tunability from its elastic properties[1], our present device uses an applied AC field to perturb the particle trajectories in the pressure-driven flow and is thereby capable of scanning the critical size over a range of factor two. Potential benefits include: extended dynamic range, facilitated fabrication and less clogging for given particle sizes, and combination of the precision afforded by DLD with the versatility of DEP.
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| 8. |
- Beech, Jason, et al.
(author)
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Stretching the limits of separation
- 2006
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In: Book of abstracts: Intl Conf on Nanosci and Technol, Basel, Switzerland (2006).
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Conference paper (peer-reviewed)
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| 9. |
- Beech, Jason, et al.
(author)
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Tipping the balance of deterministic lateral displacement devices using dielectrophoresis.
- 2009
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In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 9:18, s. 2698-2706
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Journal article (peer-reviewed)abstract
- We report the use of dielectrophoresis (DEP) to achieve tunability, improve dynamic range and open up for the separation of particles with regard to parameters other than hydrodynamic size in deterministic lateral displacement (DLD) devices. DLD devices have been shown capable of rapidly and continuously separating micrometer sized plastic spheres by size with a resolution of 20 nm in diameter and of being able to handle the separation of biological samples as wide ranging as bacterial artificial chromosomes and blood cells. DEP, while not exhibiting the same resolution in size separation as DLD, has the benefit of being easy to tune and can, by choosing the frequency, be used to probe a variety of particle properties. By combining DLD and DEP we open up for the advantages, while avoiding the drawbacks, of the two techniques. We present a proof of principle in which the critical size for separation of polystyrene beads is tuned in the range 2-6 microm in a single device by the application of moderate (100 V cm(-1)), low frequency (100 Hz) AC electric fields. The behaviour of the device was further investigated by performing simulations of particle trajectories, the results of which were in good qualitative agreement with experiments, indicating the potential of the method for tunable, high-resolution separations with respect to both size and polarisability.
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| 10. |
- Beech, Jason, et al.
(author)
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Tuneable separation in elastomeric microfluidics devices.
- 2008
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In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 8:5, s. 657-659
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Journal article (peer-reviewed)abstract
- We describe how the elastomeric properties of PDMS (polydimethylsiloxane) can be utilised to achieve tuneable particle separation in Deterministic Lateral Displacement devices via strain controlled alteration of inter-obstacle distances, a development that opens up new avenues toward more effective separation of particles in microfluidics devices.
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| 11. |
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| 12. |
- Bilenberg, B, et al.
(author)
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Topas-based lab-on-a-chip microsystems fabricated by thermal nanoimprint lithography
- 2005
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In: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 23:6, s. 2944-2949
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Journal article (peer-reviewed)abstract
- We, present a one-step technology for fabrication of Topas-based lab-on-a-chip (LOC) microsysterris by the use of thermal nanoimprint lithography (NIL). The technology is demonstrated by the fabrication of two working devices: a particle separator and a LOC with integrated optics for absorbance measurements. These applications demonstrate the fabrication of millimeter to micrometer-sized structures in one lithographic step. The use of NIL makes the technology easily scalable into the nanometer regime by the use of a suitable lithographic technique in the fabrication of the stamp. Processing issues such as environmental stress cracking of the Topas and the requirements to anti-sticking layers on the stamp when imprinting into Topas are discussed.
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| 13. |
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| 14. |
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| 15. |
- Dahlin, Andreas, et al.
(author)
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Improving the instrumental resolution of sensors based on localized surface plasmon resonance
- 2006
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 78:13, s. 4416-4423
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Journal article (peer-reviewed)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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| 16. |
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| 17. |
- Gunnarsson, Anders, et al.
(author)
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Single-molecule Detection and Mismatch Discrimination of Unlabeled DNA Targets
- 2008
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 8:1, s. 183-188
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Journal article (peer-reviewed)abstract
- We report on a single-molecule readout scheme on total internal reflection fluorescence microscopy (TIRFM) demonstrating a detection limit in the low fM regime for short (30-mer) unlabeled DNA strands. Detection of unlabeled DNA targets is accomplished by letting them mediate the binding of suspended fluorescently labeled DNA-modified small unilamellar vesicles (Ø approximately 100 nm) to a DNA-modified substrate. On top of rapid and sensitive detection, the technique is also shown capable of extracting kinetics data from statistics of the residence time of the binding reaction in equilibrium, that is, without following neither the rate of binding upon injection nor release upon rinsing. The potential of this feature is demonstrated by discriminating a single mismatch from a fully complementary sequence. The success of the method is critically dependent on a surface modification that provides sufficiently low background. This was achieved through self-assembly of a biotinylated copolymer, Poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) on a silicon dioxide surface, followed by subsequent addition of streptavidin and biotinylated DNA. The proposed detection scheme is particularly appealing due to the simplicity of the sensor, which relies on self-assembly principles and conventional TIRFM. Therefore, we foresee a great potential of the concept to serve as an important component in future multiplexed sensing schemes. This holds in particular true in cases when information about binding kinetics is valuable, such as in single nucleotide polymorphism diagnostics.
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| 18. |
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| 19. |
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| 20. |
- Jönsson, Peter, et al.
(author)
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A Method Improving the Accuracy of Fluorescence Recovery after Photobleaching Analysis
- 2008
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In: Biophysical Journal. - : Biophysical Society. - 0006-3495 .- 1542-0086. ; 95:11, s. 5334-5348
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Journal article (peer-reviewed)abstract
- Fluorescence recovery after photobleaching has been an established technique of quantifying the mobility of molecular species in cells and cell membranes for more than 30 years. However, under nonideal experimental conditions, the current methods of analysis still suffer from occasional problems; for example, when the signal/noise ratio is low, when there are temporal fluctuations in the illumination, or when there is bleaching during the recovery process. We here present a method of analysis that overcomes these problems, yielding accurate results even under nonideal experimental conditions. The method is based on circular averaging of each image, followed by spatial frequency analysis of the averaged radial data, and requires no prior knowledge of the shape of the bleached area. The method was validated using both simulated and experimental fluorescence recovery after photobleaching data, illustrating that the diffusion coefficient of a single diffusing component can be determined to within similar to 1%, even for small signal levels (100 photon counts), and that at typical signal levels (5000 photon counts) a system with two diffusion coefficients can be analyzed with less than 10% error.
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| 21. |
- Jönsson, Peter, 1981, et al.
(author)
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Mechanical Behavior of a Supported Lipid Bilayer under External Shear Forces
- 2009
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 25:11, s. 6279-6286
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Journal article (peer-reviewed)abstract
- Shear forces from a pressure-driven bulk flow in a microfluidic channel can be used to induce and control the motion of a supported lipid bilayer (SLB) formed on the walls of the channel. We here present a theoretical model that relates the experimentally observed drift velocities of an egg yolk phosphatidylcholine (egg PC) SLB to the hydrodynamic drag force from the bulk flow, the intermonolayer friction coefficient, b, of the bilayer, and the friction coefficient, b(ls) between the lower leaflet of the bilayer and the supporting substrate. The drift velocity and diffusivity of the lipids in the SLB were obtained by photobleaching a delimited area of fluorescently labeled lipids and subsequently monitoring the recovery and convective motion of the bleached spot. A striking observation was that the drift velocity of the lipids was observed to be nearly 6 orders of magnitude smaller than the bulk velocity at the center of the channel. This predicts a value for b(ls) that is at least 25 times as high as predicted by the traditional model with the SLB and the support spaced by a homogeneous 1 nm thick film of water. In addition, the intermonolayer friction coefficient was estimated to 2 x 10(7) Pa s/m, a value that increased after addition of glycerol to the bulk solution. This increase was accompanied by an equal decrease in the lipid diffusivity, with both observations indicating an increased viscous drag within the bilayer when glycerol was added to the bulk solution.
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| 22. |
- Jönsson, Peter, 1981, et al.
(author)
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Shear-Driven Motion of Supported Lipid Bilayers in Microfluidic Channels
- 2009
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:14, s. 5294-5297
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Journal article (peer-reviewed)abstract
- In this work, we demonstrate how a lateral motion of a supported lipid bilayer (SLB) and its constituents can be created without relying on self-spreading forces. The force driving the SLB is instead a viscous shear force arising from a pressure-driven bulk flow acting on the SLB that is formed on a glass wall inside a microfluidic channel. In contrast to self-spreading bilayers, this method allows for accurate control of the bilayer motion by altering the bulk flow in the channel. Experiments showed that an egg yolk phosphatidylcholine SLB formed on a glass support moved in a rolling motion under these shear forces, with the lipids in the upper leaflet of the bilayer moving at twice the velocity of the bilayer front. The drift velocity of different lipid probes in the SLB was observed to be sensitive to the interactions between the lipid probe and the surrounding molecules, resulting in drift velocities that varied by up to I order of magnitude for the different lipid probes in our experiments. Since the method provides a so far unattainable control of the motion of all molecules in an SLB, we foresee great potential for this technique, alone or in combination with other methods, for studies of lipid bilayers and different membrane-associated molecules.
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| 23. |
- Long, Brian R, et al.
(author)
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Multidirectional sorting modes in deterministic lateral displacement devices.
- 2008
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In: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 78:4 Pt 2
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Journal article (peer-reviewed)abstract
- Deterministic lateral displacement (DLD) devices separate micrometer-scale particles in solution based on their size using a laminar microfluidic flow in an array of obstacles. We investigate array geometries with rational row-shift fractions in DLD devices by use of a simple model including both advection and diffusion. Our model predicts multidirectional sorting modes that could be experimentally tested in high-throughput DLD devices containing obstacles that are much smaller than the separation between obstacles.
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| 24. |
- Mansson, A, et al.
(author)
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Actin-based molecular motors for cargo transportation in nanotechnology - Potentials and challenges
- 2005
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In: IEEE Transactions on Advanced Packaging. - 1521-3323. ; 28:4, s. 547-555
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Journal article (peer-reviewed)abstract
- Here, we review the use of actin-based motors, (myosins; e.g., the molecular motor of muscle) in. nanotechnology. The review starts from the viewpoints of the molecular motors as being important devices responsible of cargo transportation in the cell and end in discussions about their employment in nanotechnological applications. First, we describe basic biophysics of the myosin motors with focus on their involvement in cargo transportation in the living cell, leading us over into a discussion about in vitro motility assays. These are biological test systems where the myosin-induced translocation of actin filaments is studied on an artificial surface outside the cell. Then follows a review about modified motility assays for production of ordered motion. Here, we discuss ours and others' work with regards to making micro- and nanostructured surfaces and channels where the position and direction of movement produced by molecular motors is controlled. In this section, we consider the role of the channel size in promoting unidirectional myosin-induced motion of actin filaments. Furthermore, we consider the usefulness of surface modifications, e.g., various silanization procedures in order to promote and hinder molecular motility, respectively. Particularly, we describe our latest test system being both morphologically and chemically nanostructured giving us unsurpassed possibilities to perform functional studies as well as extremely good spatio-temporal control. Then follows a section about nanotechnological cargo transportation systems based on the actomyosin motor system. For instance, we present results of attaching fluorescent quantum dots as cargoes to the actin filaments. In this section, we also discuss the possibilities of having cargo attachment and detachment being performed on demand. Finally, we consider the usefulness of molecular motors for lab-on-a-chip applications and the requirements for incorporating these motors in commercially viable devices. In this context, the significant potential of the actomyosin motor system to overcome traditional limitations of micro- and nanofluidics is stressed.
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| 25. |
- Marie, Rodolphe, et al.
(author)
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A generic surface modification strategy for sensing applications based on Au/SiO2 nanostructures
- 2007
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In: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 2:1, s. 49-55
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Journal article (peer-reviewed)abstract
- A generic protocol for the creation of material-mediated self-assembled patterns of streptavidin, defined solely by patterns of gold and SiO2, is presented. Protein-adsorption resistance of selected regions was obtained by material-specific adsorption of thiol-modified poly(ethylene)glycol (thiol-PEG) on gold followed by adsorption of poly-L-lysine (PLL) modified PEG (PLL-g-PEG) on SiO2. Selective streptavidin binding to either gold or SiO2 (or both) was ensured by introducing biotin-modified thiolated (thiol-biotin) and/or biotin-modified PLL-g-PEG (PLL-g-PEGbiotin) compounds. The introduction of biotin did not influence the protein-adsorption resistance. On the macroscopic scale, the protein-adsorption-resistant properties and the streptavidin-binding capacity were optimized using quartz crystal microbalance with dissipation monitoring. The reproduction of micrometer-scale gold patterns on SiO2 into patterns of streptavidin was verified using fluorescence microscopy, while the compatibility of the material-specific surface-modification strategy with nanoscale features was accomplished by modifying a localized surface plasmon resonance (LSPR) active template, defined by randomly distributed nanoapertures in a thin gold film on SiO2. The demonstrated compatibility of the latter substrate with LSPR-based label-free sensing of biorecognition reactions, combined with the fact that all compounds utilized are commercially available, makes the surface-modification protocol attractive as a generic surface modification solution for a broad range of biorecognition-based assays. (C) 2007 American Vacuum Society.
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