Optical and electrochemical characterization of electropolymerized PEDOT:PSS on biocompatible SPR chips in view of advanced, wearable and implantable biosensors development

Abstract

This thesis describes the electropolymerization of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) on the gold layer of chips employed in surface plasmon resonance (SPR) applications, and their electrochemical and optical characterization. The main objective was to explore a novel technique for coating both conventional glass-based SPR chips and cellulose diacetate (CDA), a biopolymer, with conductive polymer films. The focus was on leveraging biodegradable and biocompatible materials in SPR applications without compromising electrical or optical performance. To characterize the modified surfaces, electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and surface plasmon resonance imaging (SPRi) were employed. EIS provided a detailed assessment of the electrical properties, particularly focusing on the charge transfer and capacitance capabilities of the PEDOT:PSS modified chips. Simultaneously, SPRi monitored the uniformity of polymer film and its growth over time on both glass and CDA substrates. These characterization methods validated the successful electropolymerization of PEDOT:PSS, indicating that the process effectively produces these films both on conventional and biopolymeric chips. A significant aspect of this study involved the use of stereolithographic (STL) 3D printing technology to create custom electrochemical cells for EIS, optimizing the measurements for precise control and reproducibility. The experimental results, supported by CA and EIS, showed that CDA-based SPR chips performed similarly to the glass chips. Moreover, PEDOT:PSS films on CDA offer electrochemical stability, indispensable for further applications in biosensing. Therefore, CDA can indeed serve as a suitable substrate in SPR technologies, particularly for applications where biocompatibility is vital, such as wearable or implantable devices. CDA was successfully integrated into SPR technology, providing the foundation to further develop highly performant optical and electrochemical sensing platforms that prioritize biocompatibility and biodegradability.