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A Label-free Technique for the Spatio-temporal Imaging of Single Cell Secretions
Published on: November 23, 2015
A single molecule immunoassay by localized surface plasmon resonance.
Kathryn M Mayer1, Feng Hao, Seunghyun Lee
1Department of Physics and Astronomy, Rice University, Houston, TX, USA.
Nanotechnology
|June 3, 2010
Summary
This study demonstrates single molecule detection using localized surface plasmon resonance (LSPR) by observing antibody-antigen unbinding events. This plasmonic sensing method achieves the ultimate limit for detecting individual molecules.
Area of Science:
- Nanotechnology
- Biophysics
- Spectroscopy
Background:
- Noble metal nanoparticles exhibit localized surface plasmon resonance (LSPR) due to electron excitation.
- LSPR frequency shifts with the surrounding refractive index, enabling sensing applications.
- Previous research has not confirmed LSPR's capability for single-molecule detection.
Purpose of the Study:
- To demonstrate single-molecule detection using LSPR.
- To investigate antibody-antigen unbinding events at the single-molecule level.
- To determine if LSPR can reach the ultimate sensing limit.
Main Methods:
- Monitoring scattering spectra of individual gold bipyramids.
- Observing antibody-antigen unbinding events.
- Utilizing finite element simulations for analysis.
Main Results:
- Single antigen molecule unbinding caused a discrete < 0.5 nm blue-shift in plasmon resonance.
- Observed unbinding rates align with established antibody-antigen binding kinetics.
- Determined the effective refractive index of a single protein to be approximately 1.54.
Conclusions:
- LSPR enables the detection of individual molecules.
- LSPR sensing offers a powerful tool for single-molecule detection methods.
- This technique probes molecular interactions over long timescales and under natural conditions.
