10 research outputs found
Sensitive and molecular size-selective detection of proteins using a chip-based and heteroliganded gold nanoisland by localized surface plasmon resonance spectroscopy
A highly sensitive and molecular size-selective method for the detection of proteins using heteroliganded gold nanoislands and localized surface plasmon resonance (LSPR) is described. Two different heteroligands with different chain lengths (3-mercaptopionicacid and decanethiol) were used in fabricating nanoholes for the size-dependent separation of a protein in comparison with its aggregate. Their ratios on gold nanoisland were optimized for the sensitive detection of superoxide dismutase (SOD1). This protein has been implicated in the pathology of amyotrophic lateral sclerosis (ALS). Upon exposure of the optimized gold nanoisland to a solution of SOD1 and aggregates thereof, changes in the LSPR spectra were observed which are attributed to the size-selective and covalent chemical binding of SOD1 to the nanoholes. With a lower detection limit of 1.0 ng/ml, the method can be used to selectively detect SOD1 in the presence of aggregates at the molecular level
Direct Observation of Defects and Increased Ion Permeability of a Membrane Induced by Structurally Disordered Cu/Zn-Superoxide Dismutase Aggregates
Interactions between protein aggregates and a cellular membrane have been strongly implicated in many protein conformational diseases. However, such interactions for the case of Cu/Zn superoxide dismutase (SOD1) protein, which is related to fatal neurodegenerative disorder amyotrophic lateral sclerosis (ALS), have not been explored yet. For the first time, we report the direct observation of defect formation and increased ion permeability of a membrane induced by SOD1 aggregates using a supported lipid bilayer and membrane patches of human embryonic kidney cells as model membranes. We observed that aggregated SOD1 significantly induced the formation of defects within lipid membranes and caused the perturbation of membrane permeability, based on surface plasmon resonance spectroscopy, atomic force microscopy and electrophysiology. In the case of apo SOD1 with an unfolded structure, we found that it bound to the lipid membrane surface and slightly perturbed membrane permeability, compared to other folded proteins (holo SOD1 and bovine serum albumin). The changes in membrane integrity and permeability were found to be strongly dependent on the type of proteins and the amount of aggregates present. We expect that the findings presented herein will advance our understanding of the pathway by which structurally disordered SOD1 aggregates exert toxicity in vivo
Sensitive and molecular size-selective detection of proteins using a chip-based and heteroliganded gold nanoisland by localized surface plasmon resonance spectroscopy
Abstract A highly sensitive and molecular size-selective method for the detection of proteins using heteroliganded gold nanoislands and localized surface plasmon resonance (LSPR) is described. Two different heteroligands with different chain lengths (3-mercaptopionicacid and decanethiol) were used in fabricating nanoholes for the size-dependent separation of a protein in comparison with its aggregate. Their ratios on gold nanoisland were optimized for the sensitive detection of superoxide dismutase (SOD1). This protein has been implicated in the pathology of amyotrophic lateral sclerosis (ALS). Upon exposure of the optimized gold nanoisland to a solution of SOD1 and aggregates thereof, changes in the LSPR spectra were observed which are attributed to the size-selective and covalent chemical binding of SOD1 to the nanoholes. With a lower detection limit of 1.0 ng/ml, the method can be used to selectively detect SOD1 in the presence of aggregates at the molecular level.</p
Core–Satellites Assembly of Silver Nanoparticles on a Single Gold Nanoparticle via Metal Ion-Mediated Complex
We report core–satellites (Au–Ag) coupled
plasmonic
nanoassemblies based on bottom-up, high-density assembly of molecular-scale
silver nanoparticles on a single gold nanoparticle surface, and demonstrate
direct observation and quantification of enhanced plasmon coupling
(i.e., intensity amplification and apparent spectra shift) in a single
particle level. We also explore metal ion sensing capability based
on our coupled plasmonic core–satellites, which enabled at
least 1000 times better detection limit as compared to that of a single
plasmonic nanoparticle. Our results demonstrate and suggest substantial
promise for the development of coupled plasmonic nanostructures for
ultrasensitive detection of various biological and chemical analytes
On-Chip Colorimetric Detection of Cu<sup>2+</sup> Ions via Density-Controlled Plasmonic Core–Satellites Nanoassembly
We
report on an on-chip colorimetric method for the detection and
analysis of Cu<sup>2+</sup> ions via the targeted assembly of plasmonic
silver nanoparticles (2.6 nm satellites) on density-controlled plasmonic
gold nanoparticles (50 nm cores) on a glass substrate. Without any
ligand modification of the nanoparticles, by directly using an intrinsic
moiety (carboxylate ion, COO<sup>–</sup>) surrounded with nanoparticles,
the method showed a high selectivity for Cu<sup>2+</sup>, resulting
in a nearly 2 times greater optical response compared to those of
other metal ions via the targeted core–satellites assembly.
By modulating the surface chemistry, it was possible to control the
density of core gold nanoparticles on the surface, thus permitting
easy tuning of the optical responses induced by plasmon coupling generated
between each core–satellites nanostructure. Using chips with
a controlled optimal core density, we observed the remarkable scattering
color changes of the chips from green to yellow and finally to orange
with the increase of Cu<sup>2+</sup> concentration. The detection
limits of the fabricated chips with controlled core densities (ca.
1821 and 3636 particles/100 μm<sup>2</sup>) are 10 nM and 10
pM, respectively, which are quite tunable and below the level of 20
μM (or 1.3 ppm) defined by the United States Environmental Protection
Agency. The findings suggest that the method is a potentially promising
protocol for detecting small molecules with target selectivity and
the tunability of the detection limits by replacing with ligands and
adjusting core densities