Intelligent onsite dual-modal assay based on oxidase-like fluorescence carbon dots-driven competitive effect for ethyl carbamate detection.

Intelligent onsite accurate monitoring ethyl carbamate (EC, a group 2 A carcinogen) in environment is of great significance to safeguard environmental health and public safety. Herein, we reported an intelligent dual-modal point-of-care (POC) assay based on the bimetallic Mn and Ce co-doped oxidase-like fluorescence carbon dots (Ce&MnCDs) nanozyme-driven competitive effect. In brief, the oxidase-like activity of Ce&MnCDs was inhibited by thiocholine (TCh, originating from the hydrolysis of acetylcholinesterase (AChE) to acetylthiocholine (ATCh)), preventing the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenothiazine (DAP). However, with the aid of Br ₂ + NaOH, EC inactivated AChE to prevent TCh generation for re-launching the oxidase-like activity of Ce&MnCDs to trigger the oxidation of OPD into DAP, thereby outputting an EC concentration-dependent ratiometric fluorescence and colorimetric readouts by employing Ce&MnCDs and OPD as the optical signal reporters. Interestingly, these dual-modal optical signals could be transduced into the gray values that was linearly proportional to the residual levels of EC on a smartphone-based portable platform, with a detection limit down to 1.66 μg/mL, qualifying the requirements of analysis of EC residues in real samples. This opened up a new avenue for onsite assessment of the risk of residues of EC, safeguarding environmental health and public safety.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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