Surface plasmon coupled emission as a novel analytical platform for the sensitive detection of cysteine

Abstract

Thiolated amino acids are biologically important molecules due to their role in protein folding and structure. One such molecule is cysteine (Cys), which acts as a biomarker for diseases like cancer, HIV, sepsis, etc., making its rapid detection imperative and essential. In this study, we report the sensitive detection of the thiolated amino acid Cys, from the non-thiolated amino acid arginine (Arg), using the novel surface plasmon coupled emission (SPCE) platform, characterized with high signal-to-noise ratios. Our studies were performed on the conventional silver (Ag) SPCE substrate, where Cys was detected to a nanomolar level, which is a major improvement to the previously reported level of sensitivity. This can be attributed to the highly sensitive SPCE platform and the unique thiol-Ag interactions associated specifically with Cys. We have also shown the role and influence of the coating process on sensitivity of detection and substantiated the advantages of SPCE over the SPR-based strategy of detection. The simplistic and economical SPCE platform enabled the sensitive detection of Cys that is of biological and medical relevance.