Abstract
Due to the trade-off between their electrical/electrochemical performance and underwater stability, realizing polymer-based, high-performance direct cellular interfaces for electrical stimulation and recording has been very challenging. Herein, we developed transparent and conductive direct cellular interfaces based on a water-stable, high-performance poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film via solvent-assisted crystallization. The crystallized PEDOT:PSS on a polyethylene terephthalate (PET) substrate exhibited excellent electrical/electrochemical/optical characteristics, long-term underwater stability without film dissolution/delamination, and good viability for primarily cultured cardiomyocytes and neurons over several weeks. Furthermore, the highly crystallized, nanofibrillar PEDOT:PSS networks enabled dramatically enlarged surface areas and electrochemical activities, which were successfully employed to modulate cardiomyocyte beating via direct electrical stimulation. Finally, the high-performance PEDOT:PSS layer was seamlessly incorporated into transparent microelectrode arrays for efficient, real-time recording of cardiomyocyte action potentials with a high signal fidelity. All these results demonstrate the strong potential of crystallized PEDOT:PSS as a crucial component for a variety of versatile bioelectronic interfaces.
Highlights
Bioelectronic interfaces that employ diverse conductive matter to electrically interface with biological organs and tissues have been widely utilized to record various bioelectric signals, e.g., brainwaves[1,2], heart beats[3,4] and neuronal spikes[5]
To evaluate the long-term stability in an aqueous environment, the crystallized PEDOT:PSS (c-PEDOT):PSS-polyethylene terephthalate (PET) substrates were submerged into deionized water (DI) water or phosphate-buffered saline (PBS) during a designated time period, and their thicknesses, optical transmittances, and electrical conductivities were directly compared with those of the pristine PEDOT:PSS-PET substrates; i.e., a PEDOT:PSS solution was directly spin-coated on PET films without chemical cross-linkers
Unlike pristine PEDOT: PSS, which immediately dissolved after immersion in DI water (Fig. S2), c-PEDOT:PSS showed excellent adhesion on the flexible PET substrates without film dissolution or delamination (Fig. 1a)
Summary
Bioelectronic interfaces that employ diverse conductive matter to electrically interface with biological organs and tissues have been widely utilized to record various bioelectric signals, e.g., brainwaves[1,2], heart beats[3,4] and neuronal spikes[5]. In the case of cellular-level bioelectronic interfaces, direct electrical stimulation has already shown the feasibility of effectively modulating cell body migration[6,7] and neuronal outgrowth[8,9,10]. Among a variety of conductive materials, conjugated polymers have attracted researchers owing to their unique properties in conjunction with their decent electrical conductivity, electrochemical activity, optical transparency, and mechanical flexibility, which are highly beneficial for electrically monitoring and stimulating cellular activities in physiological relevant conditions, i.e., aqueous solutions with many ions and biomolecules[14]. Polypyrrole[15,16], polyaniline[17,18] and polythiophene[19,20,21] have been successfully utilized
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