Gold Nanoparticle-Assisted CRISPR-Cas12a-Based Activity Assay for Highly Sensitive Detection of Trypsin

Proteases play important roles in diverse physiological processes, and their malfunction has been implicated in various conditions and diseases. Therefore, development of sensitive methods for protease detection in clinical samples is highly desired for disease diagnosis. Herein, we report an ultrasensitive and selective CRISPR-Cas12a based fluorescent assay for trypsin activity measurement. By taking advantage of the signal amplification brought by a unique magnetic bead-gold nanoparticle assembly, which carries the peptide substrate and tens to hundreds of DNA molecules per peptide molecule, trypsin can be detected with a limit of detection reaching as low as 0.13 ng/mL. Furthermore, the sensor selectivity study was performed by examining several biomolecules commonly present in biological samples, including bovine serum albumin (BSA), human serum albumin (HSA), DNase, RNase, chymotrypsin, elastase, and thrombin. Moreover, trypsin inhibition and serum sample analysis were successfully carried out. Given the ultrahigh sensitivity, the CRISPR-based trypsin activity assay developed in this work can be used as a generic platform for developing sensors for other proteases, offering the potential as a noninvasive/minimally invasive tool for clinical diagnosis.