An iron-doped Cu₂O nanozyme enables highly sensitive colorimetric detection of vitamin E in serum

Vitamin E plays a vital role in maintaining human health as well as in the prevention and treatment of related diseases. However, current methods for detecting vitamin E suffer from complex instrumentation, high cost, and cumbersome operation, making it difficult to meet the demand for rapid detection in serum samples. Herein, we designed an iron-doped cuprous oxide (Fe-Cu₂O) nanozyme for the colorimetric detection of vitamin E in human serum. Impressively, the Fe-Cu₂O nanozyme exhibits a 7.2-fold enhancement in peroxidase (POD)-like activity compared with the pure Cu₂O nanozyme. In the presence of hydrogen peroxide (H₂O₂), the Fe-Cu₂O nanozyme catalyzes the decomposition of H₂O₂ to generate hydroxyl radicals (˙OH), thereby oxidizing colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (ox TMB). As a reducing agent, vitamin E can fade the blue ox TMB, enabling the quantitative determination of vitamin E. Under optimized experimental conditions, the as-prepared Fe-Cu₂O nanozyme achieves a linear detection range of 2-80 µM toward vitamin E with a limit of detection (LOD) of 1.89 µM. This approach holds promise as a straightforward, economical, and highly effective strategy for clinical diagnosis and health screening of vitamin E and other bioactive molecules.