Neural stem cell differentiation by electrical stimulation using a cross-linked PEDOT substrate: Expanding the use of biocompatible conjugated conductive polymers for neural tissue engineering.

BACKGROUND The use of conjugated polymers allows versatile interactions between cells and flexible processable materials, while providing a platform for electrical stimulation, which is particularly relevant when targeting differentiation of neural stem cells and further application for therapy or drug screening. METHODS Materials were tested for cytotoxicity following the ISO10993-5. PEDOT PSS was cross-linked. ReNcellVM neural stem cells (NSC) were seeded in laminin coated surfaces, cultured for 4 days in the presence of EGF (20 ng/mL), FGF-2 (20 ng/mL) and B27 (20 μg/mL) and differentiated over eight additional days in the absence of those factors under 100Hz pulsed DC electrical stimulation, 1V with 10 ms pulses. NSC and neuron elongation aspect ratio as well as neurite length were assessed using ImageJ. Cells were immune-stained for Tuj1 and GFAP. RESULTS F8T2, MEH-PPV, P3HT and cross-linked PEDOT PSS (x PEDOT PSS) were assessed as non-cytotoxic. L929 fibroblast population was 1.3 higher for x PEDOT PSS than for glass control, while F8T2 presents moderate proliferation. The population of neurons (Tuj1) was 1.6 times higher with longer neurites (73 vs 108 μm) for cells cultured under electrical stimulus, with cultured NSC. Such stimulus led also to longer neurons. CONCLUSIONS x PEDOT PSS was, for the first time, used to elongate human NSC through the application of pulsed current, impacting on their differentiation towards neurons and contributing to longer neurites. GENERAL SIGNIFICANCE The range of conductive conjugated polymers known as non-cytotoxic was expanded. x PEDOT PSS was introduced as a stable material, easily processed from solution, to interface with biological systems, in particular NSC, without the need of in-situ polymerization.