Breaking the pH limitation and boosting peroxidase-like activity of Au aerogels via amalgam strategy for sensitive colorimetric bioassay

Acetylcholinesterase is a crucial enzyme in nervous systems to regulate the levels of the neurotransmitter acetylthiocholine, and organophosphorus pesticides as environmental pollutants are irreversible harmful inhibitors to acetylcholinesterase. The sensitive detection of acetylcholinesterase activity and organophosphorus inhibitors is crucial for the timely diagnosis and treatment of neurological disorders and the protection of the ecosystem. Nanozyme-based colorimetric assays are gaining popularity due to their cost-effectiveness, user-friendly procedures, and quick responsiveness, leading to their utilization in evaluating acetylcholinesterase activity and organophosphorus levels. Herein, we successfully developed core-shell AuHg aerogels with a notable peroxidaselike activity to precisely monitor acetylcholinesterase activity and organophosphorus through a cascade biocatalysis system in a nearly neutral pH environment. The coating of Hg on the surface of Au nanowires resulted in a more than tenfold enhancement in the peroxidase-like activity. Moreover, the introduction of Hg alters the electronic properties of Au aerogels, endowing them with the ability to break the acidic pH limitation of Au aerogels. Therefore, a reliable colorimetric biosensor for acetylcholinesterase activity is developed based on the inhibition effect of thiocholine on the peroxidase-like activity of AuHg aerogels. Leveraging the inhibitory effects of organophosphorus on acetylcholinesterase activity, an organophosphorus biosensor is further fabricated with excellent sensitivity (limit of detection: 0.86 ng/mL), robust anti-interference capability, and stable reproductivity. This study presents an advanced methodology for designing and synthesizing highly effective nanozymes, which pave the way for developing superior nanozyme-based colorimetric biosensors.