PtCu nanocages with superior tetra-enzyme mimics for colorimetric sensing and fluorescent sensing dehydroepiandrosterone

Nanozymes are a type of artificial enzymes that can replace traditional natural enzymes for biotechnology to biosensing, biocatalysis, and biological imaging. Nevertheless, it is still a huge challenge in the pursuit of new mimic enzymes or multiple enzyme-like activities mimics. In this work, PtCu nanocages (PtCu NCs) with hollow interior and rough exterior was prepared. PtCu NCs displayed superior tetra-enzyme mimetic activities including peroxidase (POD)-, superoxide dismutase (SOD)-, catalase (CAT)- and ascorbic acid oxidase (AAO)-like activities. Meaningfully, attributed to the POD mimic activity, sensitive and convenient colorimetric biosensors for L-Cysteine (L-Cys), homocysteine (Hcy) and glutathione (GSH) were developed with wide linear range (LR) and low limit of detection (LOD) of 0.28 μM, 1.48 μM and 0.75 μM (S/N = 3), respectively. Moreover, based on the AAO mimic activity, the cascade reaction was proposed including the oxidation of ascorbic acid (AA) to dehydroascorbic acid (DHAA) by PtCu NCs and the formation of the fluorescent quinoxaline (DFQ) coming from the reaction between DHAA and o-phenylenediamine (OPD). A novel fluorescent biosensor for dehydroepiandrosterone (DHEA) was successfully constructed based on the immunoassay method combined with the cascade reaction for AA, with the LR of 0.6–464.9 ng·mL−1 and LOD of 0.5 ng·mL−1. These colorimetric and fluorescent biosensors displayed outstanding performance in terms of sensitivity, specificity, and accuracy for real samples, suggesting that PtCu NCs was a promising candidate for biosensing.