Electrochemical techniques offer great opportunities
for the capture
of chemical and biological entities from complex mixtures and their
subsequent release into clean buffers for analysis. Such methods are
clean, robust, rapid, and compatible with a wide range of biological
fluids. Here, we designed an electrochemically addressable system,
based on a conducting terpolymer [P(EDOT-co-EDOTSAc-co-EDOTEG)] coated onto a carbon cloth substrate, to selectively
capture and release biological entities using a simple electrochemical
redox process. The conducting terpolymer composition was optimized
and the terpolymer-coated carbon cloth was extensively characterized
using electrochemical analysis, Raman and Fourier transform-infrared
spectroscopy, water contact angle analysis, and scanning electron
microscopy. The conductive terpolymer possesses a derivative of EDOT
with an acetylthiomethyl moiety (EDOTSAc), which is converted into
a “free” thiol that then undergoes reversible oxidation/reduction
cycles at +1.0 V and −0.8 V (vs Ag/AgCl), respectively. That
redox process enables electrochemical capture and on-demand release.
We first demonstrated the successful electrochemical capture/release
of a fluorescently labeled IgG antibody. The same capture/release
procedure was then applied to release extracellular vesicles (EVs),
originating from both MCF7 and SKBR3 breast cancer cell line bioreactors.
EVs were captured using the substrate-conjugated HER2 antibody which
was purified from commercially available trastuzumab. Capture and
release of breast cancer EVs using a trastuzumab-derived HER2 antibody
has not been reported before (to the best of our knowledge). A rapid
(2 min) release at a low potential (−0.8 V) achieved a high
release efficiency (>70%) of the captured, HER2+ve,
SKBR3
EVs. The developed system and the electrochemical method are efficient
and straightforward and have vast potential for the isolation and
concentration of various biological targets from large volumes of
biological and other (e.g., environmental) samples.