Biocompatibility of Injectable Materials

Biomaterials considered for use in regenerative medicine must possess certain basic requirements, including biocompatibility, biodegradation at a controlled rate to non-toxic breakdown products, support of cellular infiltration and tissue ingrowth, mechanical properties consistent with the requirements of the host tissue, and handling properties that facilitate ease of use in a clinical environment. Injectable biomaterials present significant advantages relative to implants, such as the ability to conform to complex anatomical defects and to be administered using minimally invasive techniques. For example, in the field of orthopedics, injectable biomaterials are of interest for a number of clinical indications, including filling of defects in trabecular bone at sites that are not weight-bearing and in contained defects where the structural bone is intact. However, injectable biomaterials also present additional challenges beyond the basic requirements for biomedical implants described above. A primary concern is the toxicity and ultimate fate of reactive intermediates that are not incorporated in the final cured product. Additionally, the injected material may have adverse effects on surrounding host tissue due to the reactivity of specific components or to the release of heat through a reaction exotherm. In some cases, the viscosity of the injected material may be too low, resulting in extravasation of the material into surrounding tissues where it has an adverse effect. Injectable biomaterials that are currently being investigated and developed as therapies for tissue engineering and regenerative medicine.