A nanosensor based on quantum-dot haptens for rapid, on-site immunoassay of cyanotoxin in environmental water

•QD-hapten nanoprobes by conjugating carboxyl QDs with aminoethyl-MC–LR were prepared for rapid and sensitive detection of MC–LR.•A simple analytical system by the integration of an optofluidic platform with QD-FRET-based competitive immunoassay was deveoped.•Using portable optofluidic platform, rapid, on-site cyanotoxin detection with enhanced sensitivity, lower reagent volumes, and simplified manipulation can be achieved.•The sensitivity, specificity, stability, and resistance to background interferents of this nanosensor are better than that of traditional techniques.

A nanoprobe based on quantum-dot (QD) haptens was synthesized by conjugating carboxyl quantum dots with aminoethyl-microcystin (MC)–leucine–arginine (LR). A two-alkyl group was introduced to supply a spacer between the QD nanoprobe and anti-MC–LR antibody to reduce the steric hindrances of immunoreaction. The sensor system based on a portable optofluidic platform exhibited a liner range of 0.10–4.0 µg/L for MC–LR with a detection limit of 0.03 µg/L. The proposed sensor has potential application in the rapid, on-site detection of MC–LR in real water samples.