Sensitive colorimetric detection of tetracycline hydrochloride and isoniazid with tyrosine‑manganese bifunctional nanozymes

The development of biomimetic multienzyme materials with green synthesis process, simple and fast synthesis, low energy consumption and high economic value remains a significant challenge. This work presents a tyrosine‑manganese (Tyr-Mn) bifunctional nanozyme synthesized via the water-induced coordination of Mn²⁺ and tyrosine, which mimics the metal center and amino acid microenvironment of cytochrome c oxidase. This nanozyme exhibits dual oxidase-like and laccase-like activities, demonstrating ultralow Michaelis constants (K_m) and exceptional substrate affinities for 3,3′,5,5′-tetramethylbenzidine (TMB) and 2,4-dichlorophenol (2,4-DCP). Leveraging its oxidase-like activity, a colorimetric method was developed for tetracycline hydrochloride (TCH) detection with a broad linear range (1–150 μM) and a low detection limit of 30.3 nM. Similarly, the laccase-like activity enabled specific detection of isoniazid (INH) across 0.2–50 μM, achieving a detection limit of 63.1 nM. Both sensing platforms were integrated with a smartphone-assisted visualization system for onsite analysis, yielding reliable performance in environmental and biological samples (e.g., pond water, blood, and urine), with recoveries comparable to those of HPLC. Mechanistic studies revealed that superoxide radicals (O₂^·-) drive enzymatic activity, whereas electrostatic interactions and hydrogen bonding underpin the inhibitory effects of TCH and INH, respectively. Notably, this work pioneers a noncopper laccase-mimetic nanozyme and highlights the potential of amino acid-microenvironment engineering for designing multienzyme systems. The Tyr-Mn platform offers a cost-effective, portable solution for monitoring antibiotic residues and tuberculosis therapeutics, advancing biosensor innovations in environmental and medical diagnostics.