Electrochemical conjugation of surface proteins for sensitive detection of breast cancer extracellular vesicles

Abstract

Breast cancer extracellular vesicles (EVs) are rich in molecular information related to breast tumors and are thus considered valuable diagnostic biomarkers. Herein, we develop a new electrochemical method for the detection of breast cancer EVs. This method employs an aptamer to achieve specific capture of target EVs and then adopts a signal generation strategy that does not depend on the expression of specific EV surface proteins, thereby ensuring an efficient and reliable signal output. Specifically, this signal generation strategy, namely, the electrochemical conjugation of surface proteins, utilizes an electric potential to facilitate the conjugation of redox-active small molecules to the tyrosine residues of EV surface proteins, introducing a large number of reaction sites within minutes. Following this, methylene blue-loaded DNA nanospheres are integrated onto the surface of target EVs through click chemistry, producing a remarkable electrochemical response. Taking HER-2 positive breast cancer EVs as models, this method exhibits a wide linear range from 100 to 1 × 10⁸ particles/mL, as well as good sensitivity with a detection limit of 65 particles/mL. Further validation using clinical samples from 5 healthy donors and 19 breast cancer patients reveals the practicality of this method in the diagnosis of HER-2 positive breast cancer. Therefore, we hope that this method can provide a valuable tool for detecting breast cancer EVs, and will have a broad application prospect based on the ubiquitous presence of tyrosine residues.