Capture-SELEX-based screening and mechanism analysis for the dual-colorimetric aptasening of microcystin in water

Microcystins (MCs), a class of cyclic heptapeptides prevalent in aquatic ecosystems, pose significant hepatotoxic, nephrotoxic, neurotoxic, and reproductive risks to both human and environmental health. Current detection methods often lack cost-effectiveness or operational simplicity, highlighting the urgent need for innovative strategies to enhance the monitoring of MCs in water and food sources. This study proposes an aptamer-based approach to address these limitations by targeting three predominant MC variants: MC-LR, MC-RR, and MC-YR. A five-segment oligonucleotide library underwent 12 rounds of Capture-SELEX to identify aptamers with pan-specificity for MCs. The lead aptamer, designated as MCs-12, exhibited high-affinity binding (Kd = 19.47 ± 5.35 nM) to all three conformers of MCs, as confirmed through colloidal gold spectrophotometry. Circular dichroism analysis, molecular docking studies, and dynamics simulations revealed potential binding interactions characterized by hydrogen bonding and hydrophobic effects. A dual-colorimetric biosensor utilizing the MCs-12 aptamer achieved dual-range linearity (0.25-10.00 ng/mL and 10.00-3000.00 ng/mL), with limits of detection (LOD) at 0.08 ng/mL and 0.14 ng/mL respectively. Application of this biosensor to lake water samples resulted in recoveries ranging from 94.24 % to 114.20 %, demonstrating robustness within complex matrices. The MCs-12 aptamer represents a promising biorecognition element for the surveillance of microcystins due to its stability and specificity advantages over traditional antibodies. Furthermore, the dual-colorimetric platform effectively bridges the gap between laboratory-grade sensitivity and field-deployable simplicity-facilitating cost-effective monitoring of microcystin contamination in environmental and food samples. This work advances the field of aptamer-based biosensing for detecting aquatic toxins.