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

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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 µM with a detection limit of 0.006 µM, 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.