Conductive modification of silk fibroin coating on ZE21C magnesium alloys: A physiochemical characterization with improved corrosion resistance and biocompatibility

In this study, conductive silk fibroin (SF) and poly (3, 4-vinyldioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) coating (SF-PEDOT: PSS) was successfully prepared on the ZE21C magnesium alloy via the chemical grafting process so as to improve corrosion resistance and achieve osteoimmunity. The microstructure, composition, surface wettability and corrosion behaviors of the coatings were investigated by SEM, EDS, FTIR, XPS, water contact angle and potentiodynamic polarization test. Results revealed that the chemical grafting of SF-PEDOT: PSS coating occurred, wherein, SF reacted with polydopamine to form –CO–NH- bond, and PEDOT: PSS reacted with polydopamine to form NH3+ bond. In addition, one order of magnitude reduction of corrosion density (icorr) as well as the positively shifted corrosion potential (Ecorr) by 107 mV as compared with that of the substrate was observed. Cytocompatibility results demonstrated that this coating could highly facilitate the adhesion, spreading, and proliferation of bone healing related cells (MC3T3-E1 and RAW264.7 cells). Moreover, it promoted the release of M2 phenotype factors (IL-4, IL-10 and TGF-β1), but inhibited the release of M1 phenotype factors (IL-6 and TNF-α), achieving the regulation of macrophage phenotype transformation. Furthermore, higher release of ALP, COL I and OCN revealed the acceleration of bone mineralization. In summary, the obtained SF-PEDOT: PSS coatings possessed the remarkably improvement of anticorrosion ability and good bioactivity which can serve as a promising strategy for surface design of magnesium alloys in the orthopedic applications.