Interrogation of immunoassay platforms by SERS and SECM after enzyme-catalyzed deposition of silver nanoparticles

The manuscript demonstrates the interrogation of immunoassay platforms after enzyme-catalyzed deposition of silver nanoparticles (AgNPs) using scanning electrochemical microscopy (SECM) and surface-enhanced Raman scattering (SERS). We have selected an immunoassay model platform for the determination of residues of the antibiotic sulfapyridine in milk. The assay involves a direct competitive approach with an HRP-labeled antigen analog and selective capture antibodies immobilized on the surface of glassy carbon plates modified with protein G. Interrogation of the modified substrate by SECM and SERS was carried out after enzyme-catalyzed in-situ deposition of AgNPs. The enhanced Raman scattering for proflavine in the presence of AgNPs was used as signalling system. Hexacyanoferrate(III) was applied as the redox probe in SECM; the visualization of the deposited AgNP spots was enabled by using a competition between the SECM tip microelectrode and the modified carbon plate for the oxidation of ferrocyanide. This SECM strategy proved to be an efficient tool for the interrogation of sensing surfaces that were amplified by enzyme-catalyzed silver deposition.