Taking full advantage of the structure and multi-activities of mineralized microbial surface-displayed enzymes: Portable three-in-one organophosphate pesticides assay device

It is of great significance and challenge to design a portable on-site pesticides assay device with three functions of synchronous pretreatment, rapid colorimetric assay, and detoxication. With the development of microbial surface display technology, it is interesting to take full advantage of enzymes, structures, and mineralized layers of surface display cells. Here, we constructed a portable assay device by the simple sedimentation of the phosphatemineralized organophosphorus hydrolase-fused cells (M-OPH) on syringe filter. M-OPH was prepared by the technique fusion of microbial surface display and biomineralization. Due to the porous structure of M-OPH layer and the insertion of M-OPH into the filtration pores, the M-OPH layer-modified filter membrane can filter out smaller colored impurities in real samples, showing stronger pretreatment performance. Under the specific and high-active catalysis of M-OPH, the device showed short operation time (50 s), convenient operation, high selectivity, acceptable sensitivity and visualization, for the real-time detection of paraoxon, a typical model of organophosphorus pesticides (OPP). Interestingly, M-OPH exhibited not only 4.6-fold enhanced hydrolase activity, but also remarkable peroxidase-mimicking activity and catalytic reduction activity. So, hydrolysate of OPP could be further oxidized or reduced to low-toxic products under the tandem catalysis of OPH and copper phosphate layer. The proposed three-in-one assay device would open up a practical avenue for on-site assay of pesticides in real samples.