Electroactive biomaterials that are easily processed as scaffolds with good biocompatibility for tissue regeneration are difficult to design. Herein, the synthesis and characterization of a variety of novel electroactive, biodegradable biomaterials based on poly(3,4-ethylenedioxythiphene) copolymerized with poly(d,l lactic acid) (PEDOT-co-PDLLA) are presented. These copolymers were obtained using (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (EDOT-OH) as an initiator in a lactide ring-opening polymerization reaction, resulting in EDOT–PDLLA macromonomer. Conducting PEDOT-co-PDLLA copolymers (in three different proportions) were achieved by chemical copolymerization with 3,4-ethylenedioxythiophene (EDOT) monomers and persulfate oxidant. The PEDOT-co-PDLLA copolymers were structurally characterized by 1H NMR and Fourier transform infrared spectroscopy. Cyclic voltammetry confirmed the electroactive character of the materials, and conductivity measurements were performed via electrochemical impedance spectroscopy. In vitro biodegradability was evaluated using proteinase K over 35 days, showing 29–46% (w/w) biodegradation. Noncytotoxicity was assessed by adhesion, migration, and proliferation assays using embryonic stem cells (E14.tg2a); excellent neuronal differentiation was observed. These novel electroactive and biodegradable PEDOT-co-PDLLA copolymers present surface chemistry and charge density properties that make them potentially useful as scaffold materials in different fields of applications, especially for neuronal tissue engineering.

Electroactive biomaterials are a new generation of "smart" biomaterials based on intrinsically conducting polymers (ICP). Among them, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPy) and polyaniline (PANI) are well known conducting polymers that present excellent electrical and optical properties emerging as main candidates for potential biomedical applications. Additionally, the biodegradability of biomaterials is very useful and desirable. In this context, biodegradable polymers based on polyesters, such as poly(D,L-lactic acid) (PDLLA), polycaprolactone (PCL), and poly(glycolic acid) (PGA) appear to be promising candidates because of their good biocompatibility and, as a consequence, they have been attracting attention as sustainable alternatives for applications in medicine. Weak molecular interaction with cells, biocompatibility, biodegradability, mechanics and topography are some of the main challenges for the use of conducting polymers as biomaterials. In order to improve their own biocompatibility, the main strategies are whether by doping with specific counter ions (biodopants) or chemically modifying the monomers with different molecules. Although conventional ICPs still present low or none biodegradability, there are relatively few examples of biodegradable electroactive polymers in the literature. Recently, novel approaches have been applied to solve the problem of lack of biodegradability of conducting polymers, mainly through (1) synthesis of a modified electroactive oligomers connected via degradable ester linkages creating block copolymers and (2) synthesis of modified electroactive and biodegradable macromonomers based on polyesters used in a second step copolymerization with conductive monomers. This mini-review focuses on developing trends, challenges and summarizes the recent advances on synthesis of conducting, biodegradable and biocompatible copolymers in terms of optimizing the chemical properties to improved response toward different cells, aiming biomedical applications.

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Hydrogels underpin many applications in tissue engineering, cell encapsulation, drug delivery and bioelectronics. Methods improving control over gelation mechanisms and patterning are still needed. Here we explore a less-known gelation approach relying on sequential electrochemical–chemical–chemical (ECC) reactions. An ionic species and/or molecule in solution is oxidised over a conductive surface at a specific electric potential. The oxidation generates an intermediate species that reacts with a macromolecule, forming a hydrogel at the electrode–electrolyte interface. We introduce potentiostatic control over this process, allowing the selection of gelation reactions and control of hydrogel growth rate. In chitosan and alginate systems, we demonstrate precipitation, covalent and ionic gelation mechanisms. The method can be applied in the polymerisation of hybrid systems consisting of more than one polymer. We demonstrate concomitant deposition of the conductive polymer Poly(3,4-ethylenedioxythiophene) (PEDOT) and alginate. Deposition of the hydrogels occurs in small droplets held between a conductive plate (working electrode, WE), a printing nozzle (counter electrode, CE) and a pseudoreference electrode (reference electrode, RE). We install this setup on a commercial 3D printer to demonstrate patterning of adherent hydrogels on gold and flexible ITO foils. Electro-assisted printing may contribute to the integration of well-defined hydrogels on hybrid electronic-hydrogel devices for bioelectronics applications.

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