Magnetic Fe3O4-Au@UIO-66-NH2@toehold probe mediated fluorescent sensor for detecting ovarian cancer-specific circRNA coupled with hybridization chain reaction and the CRISPR-Cas12a system

Circular RNAs (circRNAs) represent an emerging family of noncoding transcripts defined by closed-loop architecture, which are now established as key participants in the etiology of tumorigenesis and malignant progression. While circRNAs show potential as therapeutic targets and biomarkers, the accurate detection of circRNAs remains challenging due to interference from homologous linear RNAs. In this study, an ultrasensitive method for detecting circ_0051240 based on the sulfhydrated toehold capture probe-initiator assembly-mediated hybridization chain reaction (HCR) and the CRISPR-Cas12a system was developed. The capture probe (with a toehold domain)-initiator strand duplex was ingeniously fabricated to identify the back-splice junction (BSJ) of circRNA. After magnetic enrichment and separation by the Fe 3 O 4 -Au@UIO-66-NH 2 nanocomposite, the initiator strand (H0) was delivered to trigger HCR. The HCR product dsDNA concatemers contained multiply repeated CRISPR-targetable DNA sites that were readily recognized by the CRISPR RNA (crRNA). This specific recognition and binding activated the CRISPR-Cas12a system's collateral endonuclease activity, leading to cleavage of the fluorophore-quencher (FQ) reporters and fluorescence emission at a characteristic wavelength. This design eliminated linear RNA-related interference and enhanced the detection of fluorescence intensity (FI). Under optimal conditions, the proposed HCR/CRISPR-Cas12a method exhibited a wide quantitative measurement range spanning from 45 pM up to 180 nM, achieving a notable limit of detection (LOD) of 0.03 pM. In this study, a novel circRNA sensing strategy capable of accurate and highly sensitive quantification of ovarian cancer-specific circRNA was reported. The proposed method exhibits acceptable performance when compared to present approaches.