Construction of a self-calibrating ratiometric SERS platform based on nanoenzyme-mediated antagonistic Raman signal for determination of total antioxidant capacity.

In response to the limitations of traditional total antioxidant capacity (TAC) determination methods-namely limited sensitivity and weak anti-interference ability-as well as the reliance on toxic hydrogen peroxide in conventional nanozyme-based sensing systems, silver nanoparticles (HA-AgNPs) with enzyme-mimicking catalytic activity were synthesized using hydroxylamine hydrochloride as the reducing agent. These HA-AgNPs were further integrated with the ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) substrate to construct a dual-site ratiometric sensing platform based on surface-enhanced Raman scattering (SERS). Experimental results demonstrated that HA-AgNPs efficiently catalyzed the oxidation of ABTS using dissolved oxygen from air, eliminating the requirement for externally supplied hydrogen peroxide. The resulting oxidized ABTS (oxABTS) generated a strong Raman signal at 1405 cm-1. In contrast, the antioxidant substances were capable of reducing oxABTS, resulting in a concurrent decrease in the 1405 cm-1 signal intensity and a synchronous enhancement of the 1601 cm-1 Raman band, resulting in mutually antagonistic Raman signals. Using this reverse correlation between the two characteristic peaks, a ratiometric quantitative detection method was established. The system exhibited a linear response toward ascorbic acid over a concentration range of 10-9 to 10-5 mol/L, with a limit of detection as low as 0.1 nmol/L. Overall, the developed hydrogen peroxide-free nanozyme-based SERS sensing system is simple to operate and highly sensitive, providing a promising approach for rapid screening of total antioxidant capacity in food samples.