Monitoring trace endotoxin in water is difficult because it requires highly sensitive and selective analytical methods. For the first time, a new sandwich enzyme-linked immunosorbent assay (ELISA) based on molecularly imprinted polymers (MIPs) was established for sensitive and accurate endotoxin determination. MIPs selectively recognized polysaccharides of endotoxin were prepared on the surface of microplate by dopamine self-polymerization method. The MIPs were used as capture antibodies to separate and enrich trace endotoxin selectively. Then anti-endotoxin antibodies selective to lipid A of endotoxin were applied as the primary antibodies to quantify the endotoxin captured by MIPs. With selective sample pre-treatment and ELISA together, MIP-based sandwich ELISA could detect trace endotoxin (10-5-105μg/L) in different water containing interferences (phytohemagglutinin, ions, humic acid and albumin ) at different pH levels (from 3 to 9 ) with recoveries ranged from 82.3% to 105.8%. MIP-based sandwich ELISA had higher sensitivity and wider detection linearity than limulus amoebocyte lysate assays (LAL) and indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). The MIP-based sandwich ELISA provides a sensitive, accurate and stable solution to detect trace endotoxin in water.

Figure. 1. Graphical abstract