Optical assay using B-doped core–shell Fe@BC nanozyme for determination of alanine aminotransferase

B-doped core–shell Fe@BC nanozyme was synthesized. The peroxidase (POD) like activity of Fe@BC nanozyme was studied and utilized for detecting the activity of alanine aminotransferase (ALT). In the presence of ALT as well as ALT co-substrates L-alanine and α-ketoglutarate, L-glutamate is generated. The following catalytic oxidation of L-glutamate by glutamate oxidase leads to the generation of H₂O₂. The POD-like activity of Fe@BC can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to oxTMB in the presence of H₂O₂, generating a blue-colored compound. Through the detection of the amount of H₂O₂ generated, ALT activity can be determined through measuring the absorbance intensity variation at 450 nm. The limit of detection of the assay is 4 U/L, with a linear range from 10 to 1000 U/L. For human serum samples, the ALT levels determined by our assay are comparable to those determined by the hospital with a correlation coefficient of 0.991, demonstrating the reliability of our assay results.