MOF-derived N-doped porous carbon with active magnesium sites as an efficient oxidase mimic for biosensing

Transition metal-based N-doped carbon nanozymes have received great attentions recently, while rare study is on the main group metal-based ones. Here, we designed the N-doped porous carbon with active magnesium sites (Mg/NC) via carbonizing Mg-MOF precursor. The optimized Mg/NC-0.8 displayed a sheet structure. The doping of N and Mg reduced the diffusion and electron transfer resistance, accelerated electron transfer rate, and finally boosted the catalytic activity. The Mg/NC-0.8 showed superior oxidase-like activity capable of significantly promoting 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. Relative to that of N-doped carbon (NC), the oxidase-like activity of the Mg/NC-0.8 increased by 10.94-fold. The mechanism study showed the generation of O2•−, 1O2 and •OH during Mg/NC-0.8 catalyzed TMB oxidation. The Mg/NC-0.8 displayed good affinity to TMB with a Km value of 0.169 mM. In terms of its high oxidase mimic activity, a sensitive and selective assay for detecting acetylcholinesterase (AChE) activity was set up via restraining TMB oxidation by thiocholine, which was from the AChE-induced hydrolysis of acetylthiocholine. The assay shows a linear concentration range of 0.0001 – 1 U L−1 AChE, with a detection limit of 1 × 10–4 U L−1. It was used to measure AChE activity in real samples.