Construction of liquid crystal droplet-based sensing platform for sensitive detection of organophosphate pesticide

Alkaline phosphatase (ALP), as an essential disease biomarker, widely distributes in various tissues, and plays a significant role in diagnosis and treatment of some diseases (e.g. cancers and liver dysfunction). Dichlorvos (DDVP), as one of typical organophosphate pesticide, could be hydrolyzed by ALP. In this work, we constructed a simple but robust 4-cyano-4′-pentylbiphenyl (5CB) droplet sensing platform for sensitive and convenient detection of DDVP based on its hydrolysis by ALP. The optical responses of liquid crystals (LCs) originated from controlling orientations of 5CB by using an ALP cleavable surfactant, sodium monododecyl phosphate (SMP). A dark crossed optical image of 5CB was observed due to formation of the SMP monolayer at the aqueous/LC droplet interface. Subsequently, 5CB turned to bright fan-shaped optical appearance upon addition of ALP and SMP mixture. Interestingly, LCs remained dark crossed optical images in contact with the pre-incubated mixture of DDVP and ALP. The detection limit of DDVP reached ~0.1 ng/mL. Isothermal titration calorimetry (ITC) and humam ALP ELISA kit provided strong evidence for the detection mechanism. This strategy was also used to evaluate whether the maximum pesticide residue limits of tomatoes conform to the relevant national standard requirement or not. Our study holds promise for real-time and label-free detection of pesticides with high sensitivity by employing portable LC-based sensing platform. [Display omitted] •Detection of organophosphate pesticide based on its hydrolysis by ALP.•Detection limit of DDVP is around 0.1 ng/mL.•A judgement whether the maximum pesticide residue of tomatoes is up to the national standard or not.