Nanostructured Ti-Based and Polymeric Orthopedic Implant Materials with Tailored Mechanobiocidal and Osteogenic Properties

Description

The success of artificial orthopedic implants mainly depends on osseointegration andbacterial resistance in vivo. Insufficient integration between the implants and localtissues results in loosening and detachment of prostheses and post-surgery bacterialinfection can be very serious affecting the long-term success of biomedical implants.After undesirable bacteria adhesion / proliferation and subsequent biofilm formation, itis difficult to treat and a second surgery to remove the implant may be necessary.Hence, it is imperative that orthopedic implants have both antimicrobial properties andosteoconductivity.To mimic the natural bone matrix with hierarchical nanostructures, a surface withnanotopographical cues is an effective strategy to enhance the biocompatibility as wellas osseointegration. However, conventional methods used to fabricate or modify thenanostructured surfaces of biomedical implants including etching, grit blasting, andanodization may spur microbial colonization resulting in a high chance of post-operationinfection. Loading or embedding antimicrobial agents in the near-surface ofbiomaterials may suppress infection but raise the risk of resistance to commonantibiotics and possibly produce deleterious effects on cell functions and osteogenicactivity.Some natural biological structures such as cicada/dragonfly wings have been shown tohave inherent antimicrobial characteristics due to the special nanopillar arrays on thesurface. When bacteria land on the wing, the bacterial membrane is stretched andruptured by the surface nanostructures causing their death. The favorable bactericidalproperties are attributed to physico-mechanical effects rendered by the surfacenanotopography in lieu of chemical ones. Since the use of extraneous chemicals isavoided, this purely bio-mechanical strategy has less side-effects and is generally muchsafer than chemical approaches.By taking advantage of the physicochemical differences such as size and mechanicalrigidity/fluidity between prokaryotic bacteria and eukaryotic mammalian cells and theirdifferent response to nanostructured surfaces, this project will focus on the design andpreparation of special surface nanostructures on Ti and its alloy as well as polymer-basedbiomaterials. The response of bone cells and bacteria to different nanopillarstructures with different widths, heights, spacing, shape, surface energy, rigidity, as wellas wettability and their inter-dependence will be evaluated in details. The purpose ofthis project is to fabricate mechanically-modified and clinically-viable biomaterials topreferentially enhance the biological functions of bone cells while simultaneouslyinhibiting microbial colonization without relying on foreign chemicals and antibiotics.The work is expected to have important scientific and technological significance as wellas large clinical potential.