Ultrasensitive miRNA-let-7a detection based on AgInS2 quantum dots co-sensitization and CRISPR/Cas12a induced strand displacement reaction for signal amplification

Abstract

The evolution of breast cancer is usually accompanied by abnormal expression of miRNA-let-7a. Sensitive gauging of miRNA-let-7a is crucial for breast cancer monitoring and prognosis. Herein, a novel photoelectrochemical (PEC) biosensor was served as miRNA-let-7a detection on the basis of the coupling of co-sensitization and CRISPR/Cas12a-mediated strand displacement amplification (SDA). In short, AgInS2 quantum dots (QDs), characterized by a wide visible light absorption range and a stable photocurrent response, have an obvious sensitizing effect on TiO2/Bi2MoO6. Under the condition of without miRNA-let-7a, the AgInS2 fixed DNA probe was located near the surface of the TiO2/Bi2MoO6 electrode, forming a co-sensitive structure. During the detection process, hairpin DNA2 (HP2) specifically recognized miRNA-let-7a through base complementary pairing, triggering the SDA reaction to convert massive double-stranded DNA (dsDNA). The dsDNA product then triggered CRISPR/Cas12a lateral cleavage activity, causing AgInS2-sensitized DNA to leave the electrode surface and the co-sensitization effect to disappear, further reducing the photocurrent. Using a dual effect for signal amplification, the biosensor platform had linear detection capability within the scope of 0.01–10 nM, and the detection limit was 3.35 pM. The biosensor which was fabricated effectively provided an excellent platform for the effective monitoring of various tumor biomarkers in clinical detection.