Exosome Biosensor Based on Quantum Dots-Modified Field Effect Transistor

The escalating demand for high-throughput and miniaturized biosensors has spurred significant advancements in biosensor chips. However, challenges remain in achieving high-sensitivity and specificity in miniaturized devices. Herein, we construct a sensitive exosome biosensor based on quantum dots (QDs)-modified field-effect transistor. PbS QDs were drop-coated onto the gate of a high-electron mobility transistor (HEMT), followed by surface modification with CD63 antibodies (anti-CD63) through a ligand exchange strategy, and subsequent bovine serum albumin (BSA) blocking treatment. Exosomes with CD63 proteins enriched in the surface were isolated from MCF-7 breast cancer cell lines to serve as target analytes. The specific binding events between the CD63 antigen and antibody capture exosomes onto the gate of HEMT, affecting the output current ( ${I}_{\text {D}}\text {)}$ . The synergy of the capacitance coupling effect of the modification layer and the intrinsic signal amplification capability of HEMT assists in significantly modulating the 2-D electron gas (2DEG), resulting in amplified ${I}_{\text {D}}$ . With constant gate voltage applied, the ${I}_{\text {D}}$ of the biosensor sensitively increases with exosome concentration within a wide range of $10^{{5}}$ – $10^{{9}}$ particles/mL at ${V}_{\text {D}} =3.5$ V, and the limit of detection (LOD) is estimated to be $9\times 10^{{4}}$ particles/mL. This exosome biosensor demonstrates its potential for clinical applicability and paves the way for the development of miniaturized exosome biosensor chips.