Development of gold nanoparticles composite functionalized bimetallic metal-organic framework nanozymes and integrated smartphone to detection isoniazid

It is still an issue of continuous exploration to construct nanozymes with improved activity and to investigate catalytic mechanism. This study develops an open metal nodes integration strategy to prepare functionalized bimetallic metal-organic frameworks nanozymes (NMOF-CoFe1.8). Then Au nanoparticles are grown in-situ utilizing electrostatic effects to acquire composite nanozymes (Au@NMOF). Functionalization leads to deficiency of ligand in MOF and Au nanoparticles alter the surface charge to attract the chromogenic substrate with opposite charge. One-dimensional mixed-valence metal-oxygen chains with open sites inside Au@NMOF constitute sub-nanochannels with the functions of isolating external environment and transporting substances. Cobalt adsorption centers, iron and gold catalytic centers realizes the catalytic microenvironment, enhances the mass and electron transfer rate and speeds up the generation of hydroxyl radicals. The Michaelis constant of H2O2 is 0.0664 mM and of 3,3′,5,5′-tetramethylbenzidine is 0.0879 mM, which all proves its excellent activity. As non-competitive enzyme inhibitor, isoniazid forms irreversible ternary complex with the chromogenic substrate and Au@NMOF, whose inhibition constant is 0.0229 mmol. A colorimetric sensing platform with integrated smartphone based on hydrogel is constructed to detect isoniazid. The linear of isoniazid colorimetric sensing is 0.25–120 μM with the low detection limits of 0.2 μM. The assay platform is successfully applied to the human urine and serum samples assay with the recoveries of 97.0–103.72% and relative standard deviations less than 3%. It is expected to be practically applied due to its good reproducibility, feasibility and portability.