Development and use of a polylactic acid electret to stimulate bone growth

Bone remodeling and regeneration has perplexed the scientific community for ages. This project explores the possibility of stimulating bone regeneration at the sight of a circular femoral defect in rabbits through the implantation of a polylactic acid electret. Polylactic acid (PLA), a biodegradable polymer that resorbs into the body in the form of naturally occurring substances, is ideal for biomedical applications. An electret is a dielectric material that holds a semi-permanent static electrical charge. The electret is prepared via production of a polylactic acid thin film through compression molding, and then electrostatically charged using the process of corona charging. Upon completion of preparation, the electret was surgically implanted between the femur and periosteum of twelve New Zealand White rabbits. The animals were divided into four categories: Group A - four rabbits that had negatively charged films placed in contact with the defect; Group B - four animals in which a positive electret was applied to the defect; Group C - another four rabbits that served as a control group with an uncharged implant; and Group D - two animals that served as the non-surgical baseline control group to provide a guideline for comparison of the effects of surgery on the daily behavior of the animals. The animals were monitored over a period of 30 days, the time for necessary for a complete osteon, or bone cycle. Each rabbit was administered doses of tetracycline and calcein on days 21 and 27, respectively in order to calculate bone apposition rates. Final analysis of the harvested bone demonstrated that negative electrets contributed to osteoblastic activity, whereas positive electrets contributed minimally or not at all. This pilot study showed promise of future use in biomedical applications.