Polyphosphazenes as biomaterials

Biomaterials are generally “substances other than food or drugs contained in therapeutic or diagnostic systems that are in contact with tissue or biological ¥uids” (Langer and Peppas 2003). Synthetic or natural materials are thus designed to interface with biology and have been widely used for a number of biomedical applications including drug delivery devices, temporary prostheses, and tissue engineering scaffolds (Langer and Peppas 2003; Ratner and Bryant 2004). In controlled drug delivery, a biodegradable matrix that can be loaded with different biologically active molecules is preferred to release various therapeutic agents in an erosion-or diffusion-controlled fashion or a combination of both. For tissue engineering applications, a three-dimensional (3D) biodegradable scaffold that mimics the properties of various tissues is required to support cellular activities and promote neo-tissue formation. Even though biomaterials have already contributed greatly to the improvement of human health, the need for better biomaterial systems is still increasing (Ratner and Bryant 2004).