Microneedle-Based Portable Immunosensor for the On-Site Determination of Microcystin-LR without Sample Preparation in Aquatic Products

Microcystin-LR (MC-LR) contamination in aquatic products poses significant health risks, necessitating efficient, rapid field detection methods. In this work, a field-deployable, sample preparation-free MC-LR biosensor was first fabricated based on antibody-functionalized swellable microneedles (MNs), which proactively absorbed the biofluids from aquatic samples and selectively concentrated potential MC-LR molecules. Afterward, the remaining active sites of MNs were combined with known amounts of a horseradish peroxidase-labeled MC-LR antigen. Finally, the leftover free enzyme-labeled antigen was transferred to catalyze TMB/H₂O₂ substrates for signal responses, where the color intensity was proportionally correlated with the concentration of MC-LR. Sensitive analytical performance (LOD 0.22 μg/kg), reasonable recovery in spiked samples (87.6-103.4%, CVs < 10%), and accurate detection in 45 blind samples confirmed its feasibility in the real-word application. This work hybridizes the specific, swellable CS-Ab MNs with a miniaturized homemade analyzer, providing a unique, convenient, and point-of-need analytical technique for MC-LR within 30 min.