The effects of poly(3,4-ethylenedioxythiophene) coating on magnesium degradation and cytocompatibility with human embryonic stem cells for potential neural applications

Magnesium (Mg) is a promising conductive metallic biomaterial due to its desirable mechanical properties for load bearing and biodegradability in human body. Controlling the rapid degradation of Mg in physiological environment continues to be the key challenge toward clinical translation. In this study, we investigated the effects of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) coating on the degradation behavior of Mg substrates and their cytocompatibility. Human embryonic stem cells (hESCs) were used as the in vitro model system to study cellular responses to Mg degradation because they are sensitive and can potentially differentiate into many cell types of interest (e.g., neurons) for regenerative medicine. The PEDOT was deposited on Mg substrates using electrochemical deposition. The greater number of cyclic voltammetry (CV) cycles yielded thicker PEDOT coatings on Mg substrates. Specifically, the coatings produced by 2, 5, and 10 CV cycles (denoted as 2×-PEDOT-Mg, 5×-PEDOT-Mg, and 10×-PEDOT-Mg) had an average thickness of 31, 63, and 78 µm, respectively. Compared with non-coated Mg samples, all PEDOT coated Mg samples showed slower degradation rates, as indicated by Tafel test results and Mg ion concentrations in the post-culture media. The 5×-PEDOT-Mg showed the best coating adhesion and slowest Mg degradation among the tested samples. Moreover, hESCs survived for the longest period when cultured with the 5×-PEDOT-Mg samples compared with the non-coated Mg and 2×-PEDOT-Mg. Overall, the results of this study showed promise in using PEDOT coating on biodegradable Mg-based implants for potential neural recording, stimulation and tissue engineering applications, thus encouraging further research.