Ultrasensitive electrochemical detection of parvovirus B19 DNA by combining CRISPR-Cas12a and multivalent framework nucleic acids

The rapid and ultrasensitive detection of parvovirus B19 (B19V) DNA is critical for preventing severe complications in high-risk populations, such as fetal hydrops in pregnant women and aplastic crisis in immunocompromised patients. The absence of clinically approved vaccines or antivirals against B19V thus mandates the urgent development of accessible <i>in vitro</i> diagnostics to enable time-critical interventions and contain community transmission. Herein, we developed an electrochemical biosensor as a proof-of-concept for B19V by integrating CRISPR-Cas12a with multivalent framework nucleic acids (FNAs), namely, 12 nm tetrahedral DNA nanostructures (TDNs). Target B19V DNA activates Cas12a to indiscriminately cleave the biotin-modified ssDNA protruding from the four vertices of the TDNs, while the TDNs precisely orient ssDNA probes on electrodes, minimizing nonspecific adsorption. This method takes advantage of the target-specific cleavage ability of CRISPR-Cas12a (Cas12a-crRNA complex, 10-12 nm) and the unique structural and functional features of 12 nm TDNs. The comparable dimensions of the Cas12a-crRNA complex and the TDN suggest a potential synergistic effect, which contributes to the observed signal amplification and high detection sensitivity. The developed platform is user-friendly, has a low detection limit (2.19 fM), and shows high selectivity. This work establishes a foundational biosensing platform, demonstrating potential for ultrasensitive nucleic acid detection. By combining the accuracy of CRISPR-Cas12a and the benefits of FNAs, this method provides a more efficient, amplification-free, and reliable approach that holds promise for future development in point-of-care diagnostics and other applications.