We introduced a promising patterned substrate by using a microcontact printing method that can be used for SERS immunoassays based on antigen-antibody binding. SERS spectrum of the Raman reporter with antibody, which is rhodamine 6G (R6G) adsorbed on colloidal gold nanoparticles, was observed only for the surfaces in which prostate-specific antigen (PSA) is present on the substrate that is attached to an immobilized layer of antibody on the gold nanoparticles layer of the patterned substrate. Raman mapping images clearly showed that the antibodies on the Raman reporter were successfully and selectively conjugated with the antigen on the patterned substrate. This method could be potentially extended to multi-protein detections and ultrasensitive biosensors.
This paper demonstrates the potential of using a resonance Raman (RR) based method for the quantitative evaluation of protein concentrations. This method was applied to determine the concentration of bovine serum albumin (BSA) protein using zincon. In the protein-zincon liquid mixture, the number of unbound zincon molecules decreased markedly as the protein concentration increased because of the high affinity of zincon for proteins. We successfully detected very low concentrations of BSA (∼1 ng/ml) using this method, which demonstrates its great potential for the detection of proteins over a much wider range of concentrations in proteomic studies. This new RR-based method allows the detection of proteins in lower concentration than with the UV-vis-based and other protein assays commonly used in biochemical laboratories.
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