Label-free fluorescent sensor for sensitive detection of ctDNA based on water stabilized CsPbBr 3 nanosheet.

The detection of circulating tumor DNA (ctDNA), as a practical liquid biopsy technique, was of great significance for the study of cancer diagnosis and prognosis. However, reported methods for detection ctDNA still have some limitations, such as tedious process and high cost. In this study, CsPbBr ₃ nanosheet (CsPbBr ₃ NS) with high water stability was prepared by etching, and its fluorescence intensity could be stably stored for 1 year. The Ti ₃ C ₂ T _x possessed high quenching efficiency for CsPbBr ₃ NS and the HOMO-LUMO orbital study revealed that the PET mechanism was responsible for fluorescence quenching. And the Ti ₃ C ₂ T _x showed stronger affinity towards single-stranded DNA (ssDNA), as compared with double-stranded DNA (dsDNA). The probe ssDNA could be adsorbed on the surface of Ti ₃ C ₂ T _x through π-π stacking. After the targets were recognized by probe ssDNA to form dsDNA, its affinity with Ti ₃ C ₂ T _x decreased and the active site of Ti ₃ C ₂ T _x recovered, causing a high quenching efficiency on CsPbBr ₃ NS. Based on this, a label-free fluorescent biosensor was designed for the sensitive detection of ctDNA (EGFR 19 Dels for non-small cell lung cancer, NSCLC). Under the optimal experimental conditions, this biosensor exhibited a detection limit of 180 fM and a linear range of 50 pM-350 pM with amplification of magnetic beads through strand displacement reaction. In addition, this sensor was applied to the detection of ctDNA in serum samples and cells lysates. This method for ctDNA detection was expected to have great potential for biomarker detection in the field of liquid biopsy.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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