Ultrasensitive determination of insulin by an unlabelled fluorescent aptasensor based on FeO@SiO and an oxadiazole compound with AIEE activity.

A novel fluorescent organic compound, OBEI, exhibiting aggregation-induced emission enhancement (AIEE) characteristics was successfully synthesized. Leveraging its unique photophysical properties, a label-free fluorescent aptasensor was developed using OBEI as the fluorescent reporter and FeO@SiO magnetic beads as the adsorption substrate. The sensing mechanism relies on the formation of an INS-Apt/OBEI complex through electrostatic and hydrophobic interactions between OBEI and the insulin-specific aptamer (INS-Apt). This complex becomes immobilized on the magnetic bead surface via hydrogen bonding. Upon insulin introduction, the strong target-aptamer affinity triggers complex dissociation from the magnetic substrate, leaving the fluorescent INS-Apt/OBEI complex in solution after magnetic separation. The fluorescent intensity of the supernatant exhibited a linear response to insulin concentrations ranging from 0.033 pM to 10 nM, achieving a remarkable detection limit of 0.01 pM (S/N = 3). The biosensor demonstrates remarkable specificity for insulin against potential interferents and has been successfully implemented for insulin determination in human serum samples.