Control of innate immune response by biomaterial surface topography, energy, and stiffness

As the focus of implantable biomaterials has shifted from bioinert implants to bioactive designs, recent research has highlighted the complex interactions between cell physiologic systems and material prop-erties, particularly physical cues. From the cells known to interact with implanted biomaterials, the re-sponse of the immune system has been a critical target of study recently. Here, we review studies charac-terizing the response of innate immune cells to various material cues, particularly of those at the surface of implanted materials. The innate immune system consists of cell types with various roles in inflammation. Neutrophils and macrophages serve both phagocytic and signaling roles, especially early in the inflammatory phase of biomaterial implantation. These cell types ultimately dictate the outcome of implants as chronic inflam-mation, fibrosis, or integration. Other cell types like dendritic cells, mast cells, natural killer cells, and innate lymphoid cells may also serve an immunomodulatory role in the biomaterial context. This review highlights recent advances in our understanding of the role of innate immunity in the response to im-plantable biomaterials as well as key mechanobiological findings in innate immune cells underpinning these advances. Statement of significance This review highlights recent advances in the understanding of the role of innate immunity in the re-sponse to implantable biomaterials, especially in neutrophils and macrophages, as well as key mechanobi-ological findings in innate immune cells underpinning these advances. Here we discuss how physico-chemical properties of biomaterials control innate immune cell behavior. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The shift towards bioactive designs in implantable biomaterials has drawn attention to the complex interactions between cell physiologic systems and material properties, particularly physical cues. Recent research has focused on understanding the response of innate immune cells, such as neutrophils and macrophages, to implanted materials, as these cells play key roles in inflammation and ultimately dictate the outcome of implants. The review also highlights key mechanobiological findings in innate immune cells that underpin our understanding of their role in the response to implantable biomaterials.