RESUMEN
We have demonstrated two significant benefits of dynamic surface enhanced raman spectroscopy (DSERS) measurements: removal of instrumental and normal Raman interferences in surface enhanced raman spectroscopy (SERS) spectroscopy and site-selective spectroscopy of adsorbate populations on SERS-active particles. Our first example of shelled nanoparticles at very low concentrations confirmed the benefit of DSERS for removal of an overwhelmingly strong solvent spectral interference. The second benefit, site selection, was demonstrated with 4-mercaptopyridine on bare Au nanoparticles to observe a small population of molecules that were spectroscopically unique from the large population of molecules on the particles. The DSERS spectrum originated from excess variance between a small population of adsorbates on the ensemble of nanoparticles.
RESUMEN
We describe a novel sandwich assay based on surface enhanced Raman scattering (SERS) comprised of buoyant silica microspheres coated with antibodies against the ß subunit of the cholera toxin (CT), and gold nanoparticles tagged with a Raman reporter, shelled with silica and coated with antibodies against the ß subunit of the CT. Together these components couple to form a sandwich which, after incubation, floats on the surface of the sample. The buoyant silica microparticle/nanoparticle reporter combination has been coined a lab on a bubble (LoB). LoB materials may provide a platform for rapid detection of antigen in solution and offers advantages over lateral flow or magnetic pull-down assays. The Raman reporter provides a unique and intense signal to indicate a positive analysis. Our limit of detection for the ß subunit of the CT in a buffer based system is 1100 ng.