Photo-controlled cascade DNA hybridization for amplified electrochemical biosensor with tunable sensing performance

Precise control of the biorecognition process in DNA biosensors, especially for those with signal amplification, remains a challenge. It is of great significance to introduce external stimuli into the DNA system for a controllable trigger of nucleic acid cascade amplification and further for excellent biosensors.

In this study, a photo-initiated hybridization chain reaction (HCR) was designed for controllable and sensitive electrochemical biosensor via the incorporation of azobenzene moiety into the assembly unit. Under the coexistence of UV light and target DNA, a number of HCR products with biotin tags were generated and fixed on the electrode surface. Subsequently, the bound streptavidin-labeled horseradish peroxidase (SA-HRP) effectively catalyzed H₂O₂-mediated oxidation of tetramethylbenzidine (TMB), producing significant electrochemical current signals. A tunable sensing performance with different dynamic response ranges and sensitivity was achieved by adjusting the number of the inserted azobenzene moieties and the control of UV light. A limit of detection as low as 2.5 fM (S/N = 3) could be obtained in the case of one azobenzene and under UV exposure. Moreover, the photo-controlled DNA biosensor exhibited good discrimination ability even against single-base mismatch and was able to be applied in serum samples.

The proposed electrochemical DNA biosensor based on dual-triggered HCR amplification may represent a promising path to achieve sensitive and accurate bioanalysis. Also, the tunable dynamic range of the developed biosensor will provide the possibility of clinical applications.