Ultra-sensitive analysis of microcystin LR using microchip based detection system

Abstract

For the detection of cyanobacterial toxin, an Enzyme-linked immunosorbent assay (ELISA) was integrated into a PDMS microchip. The conjugates of microcystin-LR (MCLR) and keyhole limpet hemocyanin (KLH) were adsorbed on the surface of polystyrene beads and these MCLR-KLH polystyrene beads were introduced into a microchamber. MCLR on the surface of polystyrene beads reacted with horseradish peroxides (HRP) conjugated anti-MCLR monoclonal antibody (mAb) which had a competitive reaction with MCLR in water sample. After the enzyme substrate 3,3,5,5-tetramethyl benzidine (TMB) was injected into the chamber and catalyzed by HRP, the color change was detected with a liquid-cord waveguide. This integration shortened the conventional ELISA analysis time from several hours to about 30 min with only 4.2 μL MCLR sample consuming which was useful for the environmental analysis. More over, troublesome operations required for ELISA could be replaced by simple operations. The microchip based detection system showed a good sensitivity of 0.05 μg/L and maintained good reliability through its quantitative range with low coefficients of variation (2.5-10.5%).