Nanomineralzyme as a novel sustainable class of nanozyme: Chalcopyrite-based nanozyme for the visual detection of total antioxidant capacity in citrus fruit

Abstract

Chemically-synthesized Nanozymes that are widely used as alternatives to enzymes face challenges such as high precursor costs, complex preparation processes, and limited catalytic efficiency. To overcome these drawbacks, we introduce naturally derived nanozymes, nanomineralzymes, as a promising alternative, offering benefits like affordability, cost-effectiveness, and scalability. Chalcopyrite (CP, CuFeS₂) was sourced from a mineral deposit, and CP nanoparticles were produced by milling. These nanoparticles exhibited strong peroxidase-like activity, achieving a low Michaelis-Menten constant using 3,3′,5,5′-tetramethylbenzidine as a substrate. Characterizations revealed the presence of cuprous, cupric, ferrous, and ferric ions in the CP mineral. The proposed mechanism involves an enhanced Fenton and Fenton-like process due to the metal ions' multi-valence states. CP nanozyme activity was inhibited to produce radicals due to hydrogen atom transfer and single electron transfer with ascorbic acid, glutathione and cysteine. The CP mineralzyme-based total antioxidant capacity probe was successfully used for detection of TAC in citrus fruits.