A label-free fluorescent magnetic dual-aptasensor based on aptamer allosteric regulation of β-lactoglobulin

We presented a label-free fluorescent biosensor based on magnetic dual-aptamer allosteric regulation of β-lactoglobulin (β-LG) detection. The bovine serum albumin (BSA) acted as the bridge to connect amino-modified magnetic beads and aptamer, which synthesized pyramid-type probes (MBAP) with high capture and reduced nonspecific adsorption. Moreover, the original aptamer was tailored and then designed as a bivalent aptamer to fabricate allosteric signal probes (ASP). The ASP can both specifically capture β-LG and output the fluorescence signal. The detection mechanism is as follows. The combination of the dual-aptamer and β-LG triggered the allosteric change, resulting in the release of SYBR Green (SG I) from the allosteric signal probe and change signals. This method exhibits a broad linear detection range from 10 ng/mL to 1 mg/mL and the limit of detection reaches as low as 8.06 ng/mL. This study provides a highly generalizable strategy for protein biomolecular detection via replacing different target aptamers.