Electrochemical Approach for Specific Capture and Rapid Release of Nanoscale Placental Extracellular Vesicles Using Aptamer-Modified Conducting Terpolymer-Coated Carbon Cloth

Nano-sized placental extracellular vesicles (nano-pEVs) are membrane-bound vesicles released into the maternal circulation during pregnancy by the syncytiotrophoblast, which covers the surface of the placenta. The nano-pEV cargo consists of proteins, lipids, and nucleic acids, which reflect the dynamic placental function during gestation. The ability to biopsy circulating nano-pEVs would aid investigations in placental functions, allowing substantial progress in obstetric care. We developed a simple and clean electrochemical methodology for the specific capture and fast release of nano-pEVs using an electrochemically switchable conducting terpolymer-functionalized carbon cloth. The conducting terpolymer was first reduced (at −0.8 V vs Ag/AgCl, 30 s in PBS) to form active thiols, which could then interact with a thiolated CD63 aptamer via oxidation (+1.0 V vs Ag/AgCl, 60 s) in PBS. Conjugation of the aptamer to the conducting terpolymer-coated carbon cloth was confirmed using SEM-EDS, FTIR, and Raman spectroscopy. As a proof of principle, thiolated fluorescently labeled CD63 aptamers were captured and released electrochemically using this technique. Thereafter, the CD63 aptamer-modified carbon cloth showed the specific capture of nano-pEVs and their subsequent release (−0.8 V vs Ag/AgCl, 120 s) following cleavage of the disulfide bond between the aptamer and the reduced terpolymer. This aptamer-modified conducting terpolymer-coated carbon cloth demonstrated good capture and release efficiencies of (2.09 ± 0.26) × 10⁸ and (1.35 ± 0.14) × 10⁸ particles, respectively, per 70 mm² of the projected area of the terpolymer-coated carbon cloth. Confocal microscopy images clearly differentiated the carbon cloth fibers with captured nano-pEVs from those after the release. To the best of our knowledge, this work has developed for the first time an efficient, rapid, and straightforward methodology for the capture and release of nano-pEVs. This effective methodology could help to quickly determine fetal abnormalities, to diagnose obstetric disease and pathogenesis throughout pregnancy.