Responsive release of guest aqueous droplet in liquid crystal droplet assists the detection of organophosphorus using commercial pregnancy test strip

Abstract

Here, we report a liquid crystal (LC) double-emulsion based system for organophosphorus (OPs) sensing by controllable release of guest aqueous droplets (GADs) cargo. First, double liquid crystal emulsion, water in liquid crystal in water (W/LC/W), with size between 4∼ 20 μm was prepared with GADs loaded at the center of liquid crystal droplet (LCD) through elasticity trap. The LCDs were monodispersed and response sensitively to amphiphilic surfactant with opposite charge. With the capability of ejecting GADs with human chorionic gonadotropin (hCG) as cargo located in LCD to continuous aqueous phase, responsive vehicles are obtained and applied in the repurposing of commercial pregnancy test strip (PTS). With hydrophobic alkyl chain and hydrophilic head, myristoylcholine (Myr) is a good amphiphilic surfactant to trigger the release of hCG, and substrate for the enzymatic hydrolysis of acetylcholine esterase (AChE). Provided with the inhibition effect of OPs to the hydrolysis ability of AChE, OPs correlate positively with the concentration of Myr, thus correlate well with the release of hCG in W/LC/W emulsion. Thus, OPs residue in river or food is readily visualized using commercial PTS.