Angiogenesis with biomaterial-based drug- and cell-delivery systems

Angiogenesis, the formation of new blood vessels from existing ones, is an important event in several biological processes, including wound healing. It plays a key role in determining the final functionality and integration of any implanted medical device. In addition, angiogenesis is a required event for organ development and has been accepted as a rate-limiting step in engineering tissue replacements. Besides these regenerative processes, uncontrolled angiogenesis is also involved in a number of pathologies, including tumor growth and metastases. Like angiogenesis, biomaterials also play a role in wound healing after medical device implantation and in tissue engineering. Interactions between the device biomaterials and host tissue will factor into the final device integration. Additionally, tissue-engineering strategies utilize biomaterials to a great extent because the paradigm of tissue engineering involves the use of cells, growth factors and scaffolding matrices in order to regenerate or replace tissue. Since almost all tissues are three-dimensional, the biomaterial scaffold plays an integral role in the paradigm. This review will emphasize the influence of biomaterials on angiogenesis as it applies to medical device implantation, tissue engineering and therapies for pathological angiogenesis.