An electrochemical biosensor for PD-L1 positive exosomes based on ultra-thin two-dimensional covalent organic framework nanosheets coupled with CRISPR-Cas12a mediated signal amplification

Programmed death-ligand 1 protein positive (PD-L1+) exosome is one of the most prospective biomarkers for the diagnosis of cancer. However, the current methods for the detection of PD-L1+ exosomes are usually laborious, time-consuming and require numerous samples. Herein, we report in this paper an electrochemical biosensor for PD-L1+ exosomes detection based on ultra-thin two-dimensional covalent organic framework nanosheets (2D COF NSs) coupled with clustered regularly interspaced short palindromic repeats (CRISPR) Cas 12a for signal amplification. Firstly, COF-367 NSs functionalized with gold nanoparticles (AuNPs) have been synthesized for the modification of the working electrode, thus the proposed sensor can show highly improved electrochemical performance. Secondly, by utilizing the trans-cleavage activity of Cas12a, this sensor can achieve very high sensitivity for the detection of PD-L1+ exosomes. With such design, the biosensor can have a linear range from 1.2 × 102 to 1.2 × 107 particles/μL with a detection limit of 38 particles/μL. Moreover, this sensor can be employed to analyze non-small cell lung cancer (NSCLC) patient serum samples, and successfully identify NSCLC patients, demonstrating the great potential in clinical applications.