Bioactive glasses (BGs) have been widely used as osteogenic and antibacterial components in polymer-based coatings on metallic implants to simultaneously combat bacterial infections and stimulate bone integration [1]. Recent investigations show that bioactive glasses with compositions based on SiO2, CaO and P2O5 exhibit osteoinductive properties and promote the gene expression of osteoblastic cells, while the incorporation of fluoride or/and copper ions in the BG structure further endows antibacterial efficacy [2]. Zein is a natural polymer with valuable film-forming property, which can be used as biocompatible and biodegradable matrix for BG fillers [3]. Among different coating techniques, electrophoretic deposition (EPD) benefits from simple processing equipment, versatility to coat complex shapes and the possibility to control the properties of the deposit by varying the process parameters [4]. Thus, the present work aims to develop coatings based the natural polymer zein and SiO2-CaO-P2O5 BG particles doped with fluoride (BG-F) and copper (BG-F-Cu) on titanium by EPD. Morphological observations demonstrated that the glass particles were homogeneously embedded in the polymeric coating matrix, while pull-off and tape tests indicated that the addition of BG particles improved the coating adhesion to the substrate. Nanoindentation measurements and scratch tests showed that zein/BG coatings possessed higher hardness and improved scratch resistance in comparison to zein/BG-F and zein/BG-F-Cu coatings. The ion substitution in the BG structure did not affect the bioactivity of the coatings as apatite formations could be detected on all composite coatings after 3 days of immersion in simulated body fluid (SBF), according to FTIR, XRD, SEM and EDX analyses. All composite coatings showed decreased wettability, higher susceptibility to collagenase degradation and lower swelling capability than pure zein coatings. Both direct and indirect cytocompatibility assays revealed significantly improved viability of osteoblast-like MG-63 cells on all composite coatings after 1 and 3 days of incubation. Moreover, the presence of ion-doped bioactive glass endowed antibacterial activity of the coatings against Gram-positive S. aureus and Gram-negative E. coli as confirmed by Alamar blue assay and SEM observations. The obtained results prove that the prepared coatings can be promising candidates to facilitate bone tissue integration and to prevent infections around orthopaedic and dental implants.
 
[1] S. Spriano et al., Acta Biomaterialia, 79, 2018, 1-22.
[2] A. Moorthi, et al., Materials Science and Engineering C, 43, 2014, 458–464
[3] N. Meyer et al., Coatings, 8, 2018, 27.
[4] E. Avcu et al., Progress in Materials Science, 103, 2019, 69-108.
 
Acknowledgement: The authors acknowledge the German Research Foundation (Deutsche Forschungsgemeinschaft DFG, project BO1191/25-1) and the European Virtual Institute on Knowledge-based Multifunctional Materials (KMM-VIN) research fellowship program for funding.