UC Riverside

Surface coating technology is a multidisciplinary field engaged in the application of a layer or multiple layers of material onto a substrate. The primary objectives are to improve functionality, durability, and protection against environmental factors. This dissertation presents three coating materials aimed at enhancing and optimizing the properties of magnesium (Mg) and its alloys for use in biomedical applications. Both in vitro and in vivo studies were conducted to investigate the performance of these surface-modified materials. Chapter 1 introduces a new surface coating composed of polydopamine (PDA) and graphene oxide (GO). This coating enhanced the corrosion resistance of the Mg alloy in aqueous conditions and presented potential in biodegradable implant applications. Chapter 2 presents an in vitro study of these coating materials, no significant toxicity to bone marrow-derived mesenchymal stem cells (BMSCs) under indirect contact conditions within 24 hours was found. The potential application of GO/PDA-coated materials in biosensing is discussed in this chapter. In Chapter 3, nanostructured oxide-coated Mg and Mg alloys were tested in a mouse infection model to evaluate their in vivo degradation, biocompatibility, and antimicrobial properties. The coated Mg samples exhibited less degradation compared to the non-coated Mg samples 10 weeks after implantation. Histological analysis revealed new bone formation around the implants. Additionally, a lower density of methicillin-resistant S. aureus (MRSA) bacteria was observed on the mouse stifle joint in the coated Mg sample groups compared to the Ti control group. In Chapter 4, micro-sized hydroxyapatite (mHA) supplemented with 30 wt. % gentamicin was used to coat Mg plates and screws. These coated Mg plates and screws were implanted into rat mandibles for a 24-week in vivo study. No detachment was observed 24 weeks after the implantation of the coated Mg samples, indicating that these implants remained securely attached to the mandibles. The Mg2+ ions released from the implants showed no significant toxicity to the rats. New bone formation was observed around the implant sites in all sample groups.