Surface Modification Strategies for Antimicrobial Titanium Implant Materials with Enhanced Osseointegration
The use of exogenous materials to replace or repair dysfunctional tissues and organs has seen dramatic improvements since the time of the ‘physician-hero’. The past three decades have heralded the advancement of various materials and technologies for medical implant devices to repair, replace or regenerate irreversibly damaged tissues. Improvement in health outcomes, evident in life expectancy increase, has brought in its wake the increased need to replace or repair tissues, particularly weight-bearing bone tissues. Titanium (Ti), a non-magnetic, corrosion resistant, osseo-integrating metal, with a higher strength-to-weight ratio than the traditional stainless steel, has emerged as the material of choice for replacing bone and other support tissues. However, the quest for improved performance (osseointegration) and reduction in implant related infection resulting in the need for resection surgeries, has necessitated the need to improve the titanium-tissue interface mediated osseointegration process, and confer antimicrobial properties to the implant material surface. In this work, a simple cost effective physical and chemical modification strategies have been developed, to alter the surface chemistry, increase the surface water wettability and confer a nano topographic characteristic to the Ti surface. These surface parameters have been demonstrated to enhance the osseointegration process. The chemical treatments resulted in oxides containing the following ions: Calcium (Ca), for improvement of osteogenic cell adhesion to Ti surface, Silver (Ag), and Zinc (Zn) for conferring antimicrobial properties to the novel surface, and their composites (CaAg, CaZn and CaZnAg), Scanning electron microscope (SEM) profiles of the modified surface suggest that, ions are chemically bound and not physically deposited onto the Ti surface. Further evidence of this is provided by the release profile of these elements from the modified surface over a 28-day period. We have also demonstrated that, the physically modified Ti surface is better at incorporating our elements of interest than the commercially pure titanium (cpTi) surface. xi The results from a Staphylococcus aureus biofilm formation assay, and U2OS bone cell adhesion and proliferation studies, suggest that, the physical modifications enhanced both the antimicrobial performance and the osteoblast-like cell adhesion and proliferation. The suggestion also is that, the incorporated Ca further enhances the adhesion and proliferation of bone-like cells, whereas Zn and markedly Ag improve the modified Ti surface’s antimicrobial properties. However, Ag alone has been shown to have a toxic effect on the bone cells; a promising combination treatment involving Ca, Zn and Ag appears to have beneficial response in all tests.
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