Hardystonite bioceramic-endowed multifunctions of polylactic acid-based composites favourable for developing next-generation fixation implants

Abstract

Developing multifunctional, biodegradable internal fixation implants with appreciable anti-infection properties is crucial for enhancing their applications in regenerative medicine. Polylactic acid (PLA)-based polymers are attracting considerable attention in biomedicine because of their biocompatibility and biodegradability, while these biological properties, though necessary, are suboptimal for internal fixation and tissue reconstruction. In order to address the potential of implant-associated anti-infections, this study developed PLA-based composites with low crystalline hardystonite (HAR) powders with/without 5% Na doping via a low-temperature calcining and melt-blending approach. The experimental results indicated that the addition of HAR or Na-HAR powder into PLA may weaken the tensile strength and maintain the flexural strength, but the Young's/elastic modulus is significantly enhanced upon the addition of 12% Na-HAR. It was evident that the introduction of inorganic powders could accelerate the in vitro biodegradation and provide an appreciable number of functional ions favorable for improving the osteogenic stem cell viability and antibacterial efficacy (>90%) against Staphylococcus aureus and Escherichia coli. Moreover, the preliminary histological observation from the muscle-embedding model confirmed that the methicillin-resistant Staphylococcus aureus-loaded implants could readily prevent local osmotic shock, alleviate acidosis, stimulate angiogenesis and overcome the infection in the soft tissue microenvironment. These findings demonstrate that the PLA/HAR composites address the many shortcomings of the PLA substrate and exhibit multifunctional potential beneficial for diverse clinical needs, especially for treating bone-injury infections.