Optical detection of organophosphorus compounds based on Mn-doped ZnSe d-dot enzymatic catalytic sensor

In this paper, we report a sensitive and selective method for detection of organophosphorus compounds (OPs) based on Mn:ZnSe d-dots-enzyme-hydrogen peroxide (H2O2) fluorescence quenching system. Acetylcholine esterase (AChE) can hydrolyze acetylcholine (ACh) to choline. Subsequently, choline oxidase (ChOx) oxidizes choline to generate H2O2. The enzyme-generated H2O2 can quench the fluorescence of Mn:ZnSe d-dots. When paraoxon are introduced in solution, it can interact with the active centers of AChE and decrease the enzyme activity. This leads to the decrease of the H2O2 production and then the fluorescence quenching rate of Mn:ZnSe d-dots. Experimental results showed that the enzyme inhibition percentage of Mn:ZnSe d-dots-ChOx-AChE-ACh system was proportional to the logarithm of paraoxon in the range 4.84×10−11 to 4.84×10−6 mol/L with the detection limit (S/N=3) of 1.31×10−11 mol/L. The proposed biosensor has been employed for quick determination of paraoxon in tap water and milk samples with satisfactory reproducibility and accuracy. This nano-biosensor was proved to be sensitive, rapid, simple and tolerance of most interfering substances.

► A novel optical biosensor for OPs determination has been constructed.
► It combines the advantages of Mn:ZnSe d-dots and specificity in enzyme reaction.
► Detection limits of the biosensor are much lower than that of reported methods.
► We successfully detect paraoxon in the real samples with satisfactory results.