PITA Fiscal Year 2007 Projects

Biomedical and Health Engineering

Novel Surface Functionalized Patterned Titanium Implants for Improved Osseointegration
Titanium implants are the most ubiquitous implant materials used for orthopedic and dental applications. Titanium is well known for its corrosion resistance and the formation of the innate oxide on the surface due to its reactive nature results in the formation of a hydrous oxide when implanted. The biocompatibility of this hydrous oxide and the formation of an apatite structure contribute to the biocompatibility of these implants. The ability of these implants to induce bone formation and the ensuing mechanisms of osseo-integration is still not very well known. Osseointegration is the process in which clinically asymptomatic rigid fixation of alloplastic materials such as titanium is achieved and maintained in bone during functional loading. This definition does not make clear the biologic processes controlling bone formation and bone maintenance at the bone to implant interface. Cellular and molecular cascades are triggered by site preparation followed by placement of the implant. The result is primary bone healing, and bone deposition around the implant. This process is both time related and dynamic. The maximum bone deposition is achieved by 3-4 months. After this time the interface is maintained by a constant resorption and apposition remodeling cycle which continues throughout life. There is therefore a need to enhance this process and reduce the time involved in osseo-integration process.

The hypothesis of this proposal is to functionalize the surface of the Ti-implant by providing a coating of a gene delivery system or growth factor to form a pattern that will help improve and expedite the osseo-integration process. This will be done by coating nanostructured calcium phosphates on the surface of the Ti implants that will be used to deliver plasmid DNA (pDNA) to the cells migrating to the surface of the implant during the healing process. The cells will therefore be transfected with the pDNA which will result in expression of the proteins to enable ossification and better tissue integration. Novel sol-gel coatings of porous hydroxyapatite (HA) on the Ti implants will be first generated onto which the nano-carriers of HA-pDNA complexes will be deposited using solution and spin coating techniques. The functionalized surfaces will then be plated with cells to study the transfection of the plasmid DNA from the surface into the plated cells. Attempts will also be made to deposit the porous HA on the Ti implants by atomic layer deposition (ALD) at Nanodynamics in addition to the sol-gel coatings.