Label-Free Detection of Ovarian Cancer Antigen CA125 by Surface Enhanced Raman Scattering

Abstract

Surface-enhanced Raman spectroscopy (SERS) has drawn attention in recent years for imaging biological molecules as an analytical tool due to its label-free approach. The SERS approach can be used in tracking organic molecules and monitoring unique Raman spectra of the organic molecules bound to metal nanoparticles (NPs). In this paper, the molecular specifity of Raman Spectroscopy was used together with self-assembled monolayer of metallic AuNPs as a sensor platform in order to detect CA125 antibody-antigen probe molecules. Highly enhanced electromagnetic fields localized around neighboring AuNPs provide hot-spot construction due to the spatial distribution of SERS enhancement on the CA125 proteins at nM concentration level. Time resolved SERS mapping of CA125 antibody and antigen couples was recorded. Even though blinking behavior was observed for some cases, vast variety SERS signals from CA125 proteins were highly reproducible. Blinking behavior is attributed to single molecular detection. Distinguished feature of SERS mapping images of CA125 antibody and antigen with such a low concentration level is very promising for this technique to be used for diagnostic purposes.