Expanded applications, shifting paradigms and an improved understanding of host–biomaterial interactions

The conventional approach to biomaterial design and development typically focuses upon the mechanical and material properties with long-term objectives that include an inert host immune response and long-lasting mechanical and structural support. The emergence of and interest in tissue engineering and regenerative medicine have driven the development of novel cell-friendly biomaterials, materials with tailored degradation rates, materials with highly specific architectures and surfaces, and vehicles for delivery of bioactive molecules, among numerous other advancements. Each of these biomaterial developments supports specific strategies for tissue repair and reconstruction. These advancements in biomaterial form and function, combined with new knowledge of innate and acquired immune system biology, provide an impetus for re-examination of host–biomaterial interactions, including host–biomaterial interface events, spatial and temporal patterns of in vivo biomaterial remodeling, and related downstream functional outcomes. An examination of such issues is provided herein with a particular focus on macrophage polarization and its implications in tissue engineering and regenerative medicine.