Self-Regulation of Resonance Energy Transfer to Electrochemiluminescence Response Tendency Conversion for Ultrasensitive Immunoassay.

The single-signal multistate conversion sensing mode not only improves detection sensitivity but also features a simple construction process and can effectively eliminate nonspecific signal interferences. The change of molecular structure and generation of new molecules are able to regulate the activation and inhibition of the resonance energy transfer (RET) mechanism more easily through the conversion of energy levels, thus realizing the on-off-on mode. In this work, a controlled release strategy was used to trigger the self-assembly of Bi2S3/BiOI heterojunctions via the release of Na2S, resulting from the specific recognition between carbohydrate antigen 242 (CA242) and its antibody. The formation of the Bi2S3/BiOI heterojunction changed the energy level of BiOI, thereby inhibiting the RET mechanism between the [Ru(dcbpy)3]Cl2 hydrogel (Ru-Hydrogel) and BiOI, and restoring the signal, achieving the on-off-on mode of the sensor. It was an effective method to directly relate the concentration of the target CA242 (10-4-103 U/mL) to the multistate conversion of the signal. The limit of detection of this sensor for CA242 reached 1.57 × 10-4 U/mL (S/N = 3), demonstrating high sensitivity. This study provided an innovative sensing strategy for fabricating electrochemiluminescence sensors in the on-off-on mode and offered a feasible method for the high-sensitivity detection of biomarkers in the analysis field.