Design of an enzyme-mimicking NiO@Au nanocomposite for the sensitive electrochemical detection of lactic acid in human serum and urine

• Enzyme-mimics of nanomaterials for LA biosensor. • Fabrication of Au dispersed flower-structured NiO nanocomposite. • Exceptional sensing performance of NiO@Au nanocomposite. • High dispersion of Au as a signal amplification element. • The present biosensor renders broad clinical and biomedical applications. Detection of lactic acid (LA) in biological systems is required for medical diagnostics and the management of numerous medical conditions due to its key active metabolic role in the production of glycogen in muscle. Herein, we report on the facile synthesis of a novel enzyme-free gold (Au) modified flower-structured nickel oxide (NiO@Au) nanocomposite through an electrochemical strategy, which resulted in the generation of a sensing electrode material with robust synergistic effects. This sensing platform contained highly porous structured NiO flowers, which provided an extensive surface area with the capacity to mimic enzymatic activity, akin to lactate dehydrogenase (LDH) and lactate oxidase (LOD), etc. for the oxidation of LA. The effective dispersion of Au on NiO further enhanced the electron transfer process at the electrode surface. The developed sensor demonstrated a low detection limit of 11.6 µM, high sensitivity of 8.0 µA/mM, a wide linear range between 100.0 µM and 0.5 M, exceptional selectivity against potential interferences such as cystamine, ascorbic acid, uric acid, and glucose, and excellent stability over repeated cycles. The developed sensor was further tested for the detection and determination of LA in human serum and urine samples, showing that this new NiO@Au nanocomposite has strong practical applicability. The present study established a novel strategy for the synthesis of a unique NiO@Au nanocomposite, while offering a powerful and reliable electrochemical platform for the sensitive detection of LA, which translates to broad applications in biomedical, food safety, and environmental monitoring.