Project Summary Magnesium (Mg) and its alloys have attracted increasing interest for use as biodegradable implants, such as fixation devices for orthopedic and cranio-maxillofacial surgeries, due to their promising mechanical and biological properties, as well as their ability to degrade and resorb in the body. The overall aim of the Phase II program is to extend encouraging Phase I results in which biodegradable magnesium beads, coated with hydroxyapatite (HA) with an incorporated antibiotic, showed significant reduction of bacterial growth-rate and retained their mechanical properties during extended immersion in simulated body fluid. Uncoated controls lost much of their mechanical strength during the immersion tests. Phase II will extend the promising results by optimizing the hydroxyapatite coating, which is applied by N2 Biomedical's proprietary process to produce a thin, durable layer at low temperature, thereby retaining the properties of the HA source material and viability of temperature-sensitive material, such as an antibiotic. We will continue to develop a coating in which the HA will not only help initiate bone growth but also regulate the dissolution rate of the magnesium substrate and the release of the antibiotic, thus preventing infection. In vivo studies will use optimized HA-coated Mg implants in a rat model to study initiation of bone-growth, implant dissolution, and antibacterial efficacy of the antibiotic that is incorporated in the coating. Success of this program could lead to reduction or elimination of the present need for a subsequent operation to remove an implant or beads from the patient. Overall success through Phase III commercialization could start a revolution in the implant industry and a significant shift of the clinical paradigm in craniofacial and orthopedic surgery by reducing cost and pain associated with revision surgeries for implant removal.

Project Narrative Millions of screws, pins, plates, beads and suture anchors are used for fixation in orthopedic and cranio- /maxilla-facial surgeries annually. Despite their widespread use, the choice of materials for these surgical fixation devices has been limited to non-degradable metals, like stainless steel and titanium (Ti) alloys, or bioabsorbable polymers, like poly-L-lactic acid (PLLA), poly-glycolic acid (PGA) and their copolymers, or polyester/ceramic composites. If successful, HA-coated Mg beads, plates, and screws could be used for craniofacial, maxillofacial, orthopedic and many other applications, especially in pediatric surgery. Considering the pain caused in young patients, surgical complication, and healthcare cost, there is a critical need in pediatric surgeries to have degradable beads, plates, and screws to eliminate the necessity of a second surgery.