An efficient electrochemical aptamer biosensor based on target-induced strand displacement amplification for the determination of doxorubicin in human serum

Doxorubicin (DOX) is a frequently prescribed chemotherapy medication for a range of cancers. It is essential to monitor the levels of doxorubicin in human biological fluids to ensure effective treatment. An efficient electrochemical sensor for amplified detection of DOX is developed in this work. The strand displacement reaction is initiated when the blocking probe, which attaches to the terminal toehold sequence of the immobilization probe, is released due to the selective recognition of DOX with the aptamer probe. The secondary toehold region is then available for hybridization with the methylene blue (MB)-labeled signal probe, causing the blocking probe to be displaced and activating the molecular machine. Consequently, the blocking probe is reused in a cyclical manner, with numerous signal probes being attached to the sensor surface, resulting in a significant increase in current for quantitative analysis. This technique successfully detected DOX in human serum samples with high selectivity and sensitivity, reaching a detection limit of 670 fM. The proposed research offers a novel approach to identifying various biomarkers, with the potential to significantly advance clinical diagnosis and drug research.