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 × 10 2 to 1.2 × 10 7 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.