Ratiometric SERS quantitative analysis of tyrosinase activity based on gold-gold hybrid nanoparticles with Prussian blue as an internal standard.

Tyrosinase (TYR) is a polyphenol oxidase that regulates melanin biosynthesis. Abnormal levels of TYR have been confirmed closely associated with melanoma cancer and other diseases, making the establishment of highly sensitive and accurate quantitative detection of TYR is thus essential for fundamental research and clinical applications. Herein, we proposed a new strategy that combines surface-enhanced Raman scattering (SERS) with Dopamine (DA) and Prussian blue (PB) functionalized gold-gold hybrid nanoparticles for TYR detection. DA is oxidized to dopaquinone with the presence of TYR, leading to the consumption of DA in the reaction solution and the corresponding decrease in DA characteristic peak intensity at 1480 cm-1. Our SERS quantitative assay of TYR with "on-off" sensing strategy yields an excellent limit of detection (LOD) of 3 × 10-3 U mL-1 in a linear range of 10-3 to 100 U mL-1. In particular, the intensity ratio of 1480 cm-1 to 2121 cm-1 allows us to achieve remarkably reliable quantitative detection of TYR, with the 2121 cm-1 peak intensity of the standard internal (IS) molecule PB being used to correct SERS signal fluctuations. Furthermore, our proposed assay has been successfully demonstrated to quantify TYR spiked in human serum samples, with excellent percentage recovery of 90.0-110.6 %. The potential of our ratiometric SERS strategy for the performance evaluation of TYR inhibitors has also been verified. Our work is therefore expected to provide a new route for accurate and reliable monitoring of TYR activity in the complex biological environment.