Confined catalysis of MOF-818 nanozyme and colorimetric aptasensing for cardiac troponin I

Understanding the catalytic performance of nanozymes assembled in confined environment is an interesting topic. Herein, a three-dimensional nanozyme-catalytic nanoreactor was constructed by confining MOF-818 nanozyme in the pore of macroporous tungsten trioxide (p-WO3). The catalytic activity of MOF-818 assembled in-situ for the oxidation of 3,5-Di-tert-butylcatechol (3,5-DTBC) could be regulated by changing the pore size of p-WO3. Only when being confined in the pores of p-WO3 with an appropriate pore size, MOF-818 could exhibit high affinity towards 3,5-DTBC, and excellent catalytic activity for 3,5-DTBC oxidation, the catalytic rate constant kcat and Michaelis constant Km were determined to be 31.47 s-1 and 1.42 mM, respectively, and the maximum yield of 3,5-DTBC oxidation reached 95.2%. Furthermore, the as-constructed nanozyme-catalytic nanoreactor could be designed to construct a colorimetric aptasensor for selective determining cardiac troponin I based on the enzymatic inhibition effect and the exonuclease I-assisted target recycling signal amplification, which exhibited a good linear range of 50 fg mL-1 - 100 ng mL-1, low detection limit of 18 fg mL-1, and was applied for human serum analysis with RSD less than 5.2% and the recoveries ranged from 95% to 107%.