Development of Biodegradable Photopolymers for Bone Tissue Engineering

Various orthopaedic methods for the fixation of fractured bone or after removal of bone tumours are currently in clinical use. Autografts, tissue obtained from another site in the same subject of the same species, are the gold standard for tissue repair and substitution. However, the use of autografts has some serious disadvantages, such as additional expense and trauma to the patient, possibility of donor site morbidity, and limited availability. In the case of allografts, in addition to limited supply and high costs, other complications such as viral transmission and immunogenicity are of serious concern. Therefore, there is a critical need to develop bone substitute materials approximating the properties of tissue, which should be replaced, but without the drawbacks of autografts or allografts. Degradable polymers that are already in clinical use usually consist of a copolymer of lactic and glycolic acid (Figure 1). These polyesters, which serve quite well for the fixation of fractured bone, cannot be used in the case of larger defects, e.g. after removal of a bone tumour, because of their hydrolytic degradation, which causes quite fast loss in mechanical strength. Moreover, the locally high concentration of free acids can result in tissue necrosis.