Conducting Polymer-Infused Electrospun Fibre Mat Modified by POEGMA Brushes as Antifouling Biointerface.

Biofouling on surfaces, caused by the assimilation of proteins, peptides, lipids and microorganisms, leads to contamination, deterioration and failure of biomedical devices and causes implants rejection. To address these issues, various antifouling strategies have been extensively studied, including polyethylene glycol-based polymer brushes. Conducting polymers-based biointerfaces have emerged as advanced surfaces for interfacing biological tissues and organs with electronics. Antifouling of such biointerfaces is a challenge. In this study, we fabricated electrospun fibre mats from sulphonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (sSEBS), infused with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) (sSEBS-PEDOT), to produce a conductive (2.06 ± 0.1 S/cm), highly porous, fibre mat that can be used as a biointerface in bioelectronic applications. To afford antifouling, here the poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes were grafted onto the sSEBS-PEDOT conducting fibre mats via surface-initiated atom transfer radical polymerization technique (SI-ATRP). For that, a copolymer of EDOT and an EDOT derivative with SI-ATRP initiating sites, 3,4-ethylenedioxythiophene) methyl 2-bromopropanoate (EDOTBr), was firstly electropolymerized on the sSEBS-PEDOT fibre mat to provide sSEBS-PEDOT/P(EDOT-co-EDOTBr). The POEGMA brushes were grafted from the sSEBS-PEDOT/P(EDOT-co-EDOTBr) and the polymerization kinetics confirmed the successful growth of the brushes. Fibre mats with 10-mers and 30-mers POEGMA brushes were studied for antifouling using a BCA protein assay. The mats with 30-mers grafted brushes exhibited excellent antifouling efficiency, ~82% of proteins repelled, compared to the pristine sSEBS-PEDOT fibre mat. The grafted fibre mats exhibited cell viability >80%, comparable to the standard cell culture plate controls. Such conducting, porous biointerfaces with POEGMA grafted brushes are suitable for applications in various biomedical devices, including biosensors, liquid biopsy, wound healing substrates and drug delivery systems.

Conducting Polymer-Coated Carbon Cloth Captures and Releases Extracellular Vesicles by a Rapid and Controlled Redox Process.

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.

Novel Electrochemically Switchable, Flexible, Microporous Cloth that Selectively Captures, Releases, and Concentrates Intact Extracellular Vesicles.

There is a significant and growing research interest in the isolation of extracellular vesicles (EVs) from large volumes of biological samples and their subsequent concentration into clean and small volumes of buffers, especially for applications in medical diagnostics. Materials that are easily incorporated into simple sampling devices and which allow the release of EVs without the need for auxiliary and hence contaminating reagents are particularly in demand. Herein, we report on the design and fabrication of a flexible, microporous, electrochemically switchable cloth that addresses the key challenges in diagnostic applications of EVs. We demonstrate the utility of our electrochemically switchable substrate for the fast, selective, nondestructive, and efficient capture and subsequent release of EVs. The substrate consists of an electrospun cloth, infused with a conducting polymer and decorated with gold particles. Utilizing gold-sulfur covalent bonding, the electrospun substrates may be functionalized with SH-terminated aptamer probes selective to EV surface proteins. We demonstrate that EVs derived from primary human dermal fibroblast (HDFa) and breast cancer (MCF-7) cell lines are selectively captured with low nonspecific adsorption using an aptamer specific to the CD63 protein expressed on the EV membranes. The specific aptamer-EV interactions enable easy removal of the nonspecifically bound material through washing steps. The conducting polymer component of the cloth provides a means for efficient (>92%) and fast (<5 min) electrochemical release of clean and intact captured EVs by cathodic cleavage of the Au-S bond. We demonstrate successful capture of diluted EVs from a large volume sample and their release into a small volume of clean phosphate-buffered saline buffer. The developed cloth can easily be incorporated into different designs for separation systems and would be adaptable to other biological entities including cells and other EVs. Furthermore, the capture/release capability holds great promise for liquid biopsies if used to targeted disease-specific markers.