A novel nanobiocomposite sandwich immunosensor based on molecularly imprinted nano-membrane for endotoxin detection

Abstract

Endotoxin in water affects water quality and human health. Detecting endotoxin in water required sensitive, accurate and stable methods due to the large amounts of interferences and highly varied endotoxin levels in different water. For the first time, a novel nanobiocomposite sandwich immunosensor was fabricated for accurate and convenient endotoxin determination by using molecularly imprinted nano-membrane (MIM) and nature antibody selective to different epitopes of endotoxin as affinity molecules simultaneously. Endotoxin-imprinted MIM was prepared on the surface of microplate by dopamine self-polymerization method. MIM enriched endotoxin by binding polysaccharides selectively. Then primary antibody specific to lipid A of endotoxin quantified the endotoxin captured by MIM. Using the high stability of MIM to harsh conditions and the high accuracy of nature antibody as affinity molecules simultaneously, selective sample pre-treatment was designed into immunosensor effectively. The achieved immunosensor detected endotoxin in different diluted or un-diluted water sensitively and accurately. The LOD, LOQ and linearity of the immunosensor were 4 × 10−6 μg/L, 1.3 × 10-5 μg/L and 10-5-105 μg/L respectively. While only proper diluted water samples could be accurately detected by limulus amebocyte lysate assays (LAL). The immunosensor also had much higher sensitivity and accuracy than indirect competitive ELISA which used the same primary antibody. By combing sample pre-treatment with immunosensor, the nanobiocomposite sandwich immunosensor provides a solution to detect endotoxin in water accurately and conveniently.