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Accurate monitoring of bleomycin (BLM) levels in clinical samples is essential for enhancing therapeutic outcomes while minimizing potential toxicity. In this study, we present a label-free fluorescent sensor for the sensitive detection of BLM, based on a cavity hairpin nucleic acid switch that activates thioflavin T (ThT) fluorescence. The engineered switch features two CGG-AAA cavities that facilitate ThT binding and fluorescence enhancement, along with a BLM-specific cleavage site (5’-GT-3’). Upon exposure to BLM, the BLM·Fe(Ⅱ)-induced DNA cleavage disrupts the hairpin structure, resulting in ThT release and a marked reduction in fluorescence intensity. Under optimized conditions, the sensor exhibits a strong linear correlation between fluorescence intensity and the logarithmic BLM concentration within the range of 10–1000 nM, achieving a detection limit of 1.26 nM. Furthermore, successful application of the sensor in human serum samples demonstrates its potential for clinical diagnostics and biomedical research.
Luo et al. (Sun,) studied this question.