Enhanced CRISPR-Cas12a Fluorescent Assay for Detecting Trace Levels of Procalcitonin

Rapid and accurate detection of procalcitonin (PCT), a major biomarker for bacterial infections and sepsis, remains a pressing need in clinical diagnostics because sepsis progresses rapidly and may initially present with nonspecific or even subtle symptoms. Herein, we report a CRISPR-Cas12a-based fluorescence biosensing platform for ultrasensitive detection of PCT. The platform employs antibody-functionalized magnetic beads (MBs) for specific protein enrichment and antibody- and oligonucleotide- dual-functionalized gold nanoparticles (AuNPs) for high-density DNA payload. After sandwich complex formation with the target PCT, a programmed ssDNA strand is released by thermal denaturation, which then activates Cas12a collateral cleavage, thereby generating a fluorescence signal. Thorough physicochemical characterizations, including zeta potential, dynamic light scattering, UV-vis spectroscopy, and TEM, were carried out to confirm the successful functionalization of MBs and AuNPs. The developed PCT sensor was highly sensitive with a limit of detection (LOD) reaching 3 pg/mL. Moreover, the biosensor exhibited an excellent specificity toward PCT against clinically relevant interferents such as C-reactive protein (CRP), interleukin-2β (IL-2β), interleukin-6 (IL-6), human serum albumin (HSA), and bovine serum albumin (BSA), and simulated serum sample analysis was successfully carried out with the recoveries ranging from 108 to 122%. The PCT sensing technique developed in this work offers the potential to be expanded to construct a multiplexing platform for simultaneous detection of multiple biomarker species for early and accurate disease diagnosis.