A novel biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) for tetracycline detection

The specificity of antibodies and efficient amplification of nucleic acid molecules play an important role in developing biosensors for monitoring human and environmental health. Herein, integrating their capabilities by site-selective modification of small molecules on DNA, a biosensor based on antibody-controlled strand displacement amplification (SDA) and hybridization chain reaction (HCR) was developed. The SDA-HCR reaction was activated by the competitive binding of antibodies to free small molecules and small molecule-conjugated DNA. As a proof-to-concept, we developed a biosensor capable of detecting tetracycline (TC) with high sensitivity and specificity. First, TC was labeled with azide group through chemical modification, and TC-DNA was prepared by copper-free click chemistry. Further, the antibody-controlled SDA-HCR reaction was developed through serial optimization. By this method, TC could be detected in a linear range of 0.01-100 mu M with a detection limit of 0.006 mu M, and the recovery of actual samples was 96.62-100.31 % with 1.70-4.00 % RSD, suggesting satisfactory performance by the biosensor. Using this method, TC or any other small molecules can be detected without washing, immobilization, and multiple additional steps, which would simplify detection to a great degree. Consequently, the distinctive strategy proposed in this work may find more applications in the detection of other small molecules.