Emulsion-templated construction of enzyme-nanozyme integrated hierarchically porous hydrogels for smartphone-assisted pesticide biosensing

Due to their great threat to human health and the environment, it is always of significance to develop efficient tools to monitor pesticide residues. Although the enzyme inhibition-based strategy is considered as a potential method and has been intensively explored for pesticide analysis, both vulnerable enzymatic activity and tedious operation greatly hinder its practical applications. Developing robust, easy-to-use and efficient devices for pesticide sensing is still challenging. Herein, we recommend an enzyme-nanozyme integrated hierarchically porous hydrogel (AChE-MnO2@HPH) for the convenient detection of pesticides. MnO2 microspheres were first employed as an emulsion stabilizer to fabricate MnO2@HPH by thermal polymerization, and AChE was then immobilized into the MnO2@HPH via a fast self-absorption process. With the unique porous structure and hydrophilic microenvironment, the constructed AChE-MnO2@HPH exhibited excellent enzymatic activity and stability as well as rapid response toward pesticides through inhibiting the activity of AChE. By applying a smartphone to read the color information originating from the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) catalyzed by oxidase-mimicking MnO2, highly sensitive and convenient determination of fenthion, an organophosphorus pesticide model, was achieved with a detection limit down to 0.63 ng mL−1. Excellent performance robustness over 30 storage days and reliable detection of the target in real food samples were also demonstrated. With the advantages of easy operability, free of equipment, and good detection performance and long-term stability, the integrated AChE-MnO2@HPH will find promising use for pesticide residue in-field analysis.