Functionalized PEDOT polymeric coatings for neuroelectrodes: topographical and biological strategies

Abstract

Event Abstract Back to Event Functionalized PEDOT polymeric coatings for neuroelectrodes: topographical and biological strategies Catalina Vallejo-Giraldo1, Eilís Dowd2, Dulcé Papy-Garcia3, Abhay Pandit1 and Manus J. Biggs1 1 National University of Ireland, Centre for Research in Medical Devices (CÚRAM), Ireland 2 National University of Ireland, Pharmacology & Therapeutics, Ireland 3 UFR Sciences et Technologie, Université Paris Est Créteil, France Introduction: Studies with conducting polymers (CPs) as functional electrode coatings have shown that they enhance tissue/electrode integration and electrode performance in situ[1]. Current strategies in this field focus on reducing impedance and the presentation of neurotropic moieties to enhance the integration with brain milieu and to help with cell attachment properties[2]. The use of biochemical functionalization of CPs surfaces is being increasingly utilized to present biologically active dopants to promote or inhibit specific biological interaction with brain cells. This study investigates a range of physical, electrical and biological properties of a conventional conducting polymer PEDOT with topographical functionalization by means of micro and nanotopographical modification, and with biological modification by entrapping the heparan sulphate mimetic F6 to support the electrode stability and electrical properties via sustained neural integration within the PEDOT electrode coating film. Experimental Methods: Topographical modification: PEDOT films were polymerized galvanostatically on platinum coated glass, and characterized by Raman spectroscopy, XPS, EIS, AFM and SEM. PEDOT films were then imprinted using photolithography fabricated Ni masters. Biological modification: PEDOT/mimetic molecule films were polymerized galvanostatically on platinum coated glass. The cytocompatibility of the functionalized PEDOT films was evaluated by culturing isolated E14 rat ventral mesencephalic (VM) cells on the polymeric films and performing quantitative immunostaining of relevant neural biomarkers such as ß tubulin for neural outgrowth and GFAP for astrocytes. Results and Discussion: The results depicted in Fig1.a and b show the topographical modification of PEDOT polymeric films after imprinting an ordered array of 1µm wide/deep pits, as a proof of concept of surface modification with topographical features. Importantly, PEDOT microimprinted films led to adhesion of primary VM cells (Fig1.c) with significant difference in neurite outgrowth compared to pristine PEDOT films depicted in Fig1.d. Also, the heparan sulphate mimetic F6 was successfully entrapped during electrodeposition and it preserved biofunctionality as assessed by the promotion of VM cells neurite outgrowth on PEDOT coating films for up to ten days in culture (Fig2.a-b). A slight decrease in percentage of astrocytes was also observed compared to pristine films (Fig2.c). Conclusion: The topographical and biological modification presented here, provide an enhancement of the PEDOT polymeric films with a promotion of healthy primary VM cells population over a period of ten days in culture. In addition, the films functionalized with the heparan sulphate mimetic F6 showed a slight but significant decrease in astrocyte population. However, this only goes part of the way to solving biological interface interaction as the physico-electrical material properties were significantly disrupted by the entrapment of the mimetic. In contrast, the topographical modified films resulted in an increase of conductive properties compared to pristine films. Functionalized conducting polymers involves creating polymers with multiple functionalities, which allow preservation of physico-electrical film’s properties, while addressing the cell interaction, selection and attachment. This work was funded through Science Foundation Ireland 11/SIRG/B2135.; MB is a funded investigator through the Science Foundation Ireland Centre for Research in Medical Devices (CÚRAM) (Grant agreement no. 13/RC/2073).