6 research outputs found
A Localized Surface Plasmon Resonance Imaging Instrument for Multiplexed Biosensing
Localized
surface plasmon resonance (LSPR) spectroscopy has been
widely used for label-free, highly sensitive measurements of interactions
at a surface. LSPR imaging (LSPRi) has the full advantages of LSPR
but enables high-throughput, multiplexed measurements by simultaneously
probing multiple individually addressable sensors on a single sample
surface. Each spatially distinct sensor can be tailored to provide
data regarding different surface functionalities or reaction environments.
Previously, LSPRi has focused on single-particle sensing where the
size scale is very small. Here, we create defined macroscale arrays
of nanoparticles that are compatible with common patterning methods
such as dip-pen nanolithography and multichannel microfluidic delivery
devices. With this new LSPR sensing format, we report the first demonstration
of multiplexed LSPR imaging and show that the increased throughput
of our instrument enables the collection of a complete Langmuir binding
curve on a single sensor surface. In addition, the multiplexed LSPR
sensor is highly selective, as demonstrated by the hybridization of
single-stranded DNA to complementary sequences immobilized on the
sensor surface. The LSPR arrays described in this work exhibit uniform
sensitivity and tailorable optical properties, making them an ideal
platform for high-throughput, label-free analysis of a variety of
molecular binding interactions
Single Plasmonic Nanoparticle Tracking Studies of Solid Supported Bilayers with Ganglioside Lipids
Single-particle tracking experiments were carried out
with gold
nanoparticle-labeled solid supported lipid bilayers (SLBs) containing
increasing concentrations of ganglioside (GM<sub>1</sub>). The negatively
charged nanoparticles electrostatically associate with a small percentage
of positively charged lipids (ethyl phosphatidylcholine) in the bilayers.
The samples containing no GM<sub>1</sub> show random diffusion in
92% of the particles examined with a diffusion constant of 4.3(±4.5)
Ă 10<sup>â9</sup> cm<sup>2</sup>/s. In contrast, samples
containing 14% GM<sub>1</sub> showed a mixture of particles displaying
both random and confined diffusion, with the majority of particles,
62%, showing confined diffusion. Control experiments support the notion
that the nanoparticles are not associating with the GM<sub>1</sub> moieties but instead most likely confined to regions in between
the GM<sub>1</sub> clusters. Analysis of the root-mean-squared displacement
plots for all of the data reveals decreasing trends in the confined
diffusion constant and diameter of the confining region versus increasing
GM<sub>1</sub> concentration. In addition, a linearly decreasing trend
is observed for the percentage of randomly diffusing particles versus
GM<sub>1</sub> concentration, which offers a simple, direct way to
measure the percolation threshold for this system, which has not previously
been measured. The percolation threshold is found to be 22% GM<sub>1</sub> and the confining diameter at the percolation threshold only
âŒ50 nm