A surface-enhanced Raman spectroscopy based smart Petri dish for sensitive and rapid detection of bacterial contamination in shrimp

Indole level in seafood induced by food-borne bacteria is a vital parameter to determine whether the seafood has bacterial contamination. Therefore, to detect pathogens and ensure food safety, rapid, easy to use, and highly sensitive analytical tools are needed for quantifying indole in seafood. In this study, we developed a highly sensitive surface-enhanced Raman spectroscopy (SERS) based tool to detect indole in shrimp. The tool relies on a smart sample container made of a gold nanosphere (AuNS) coated glass Petri dish, AuNS@Dish. The AuNS@Dish was proven to be an efficient plasmonic SERS substrate having an analytical enhancement factor (AEF) of 106. When the indole-containing shrimp extracts were incubated in the plasmonic AuNS@Dish, the SERS signal of indole was significantly enhanced due to the Raman enhancement effects of the AuNS@Dish plasmonic substrate. The change in SERS intensity as a function of indole concentration was used to construct a standard calibration curve leading to a limit of detection (LOD) of 4.97 nM for indole. The standard calibration curve allowed determination of indole level in shrimp samples as low as 0.009 μg/100 g of shrimp which is way below the FDA regulated level, i.e., 25 μg indole/100 g of shrimp. Apart from the high sensitivity, the detection technique was rapid (<10 min), easy to handle, and fulfilled requirements for determination of bacterial contamination in shrimp. Overall, this is a novel, facile, and sensitive analytical method to detect indole in shrimp with possible future applications in other seafood.