Self-healing biomaterials: from molecular concepts to clinical applications

Biomaterials are being applied in increasingly complex areas such as tissue engineering, bioprinting, and regenerative medicine. For these applications, challenging-or even contradictory-combinations of biomaterial properties are often required which cannot be met by conventional biomaterials. During the past decade, several new concepts have been developed to render biomaterials self-healing, thereby offering new opportunities to improve the functionality of traditional biomaterials in terms of their mechanical, handling, and biological properties. Consequently, various types of self-healing polymeric, ceramic, or composite biomaterials have been developed. Nevertheless, despite the rapid emergence of the field of self-healing biomaterials, this field of research has not been reviewed during the recent years. Therefore, this article provides a critical overview of recent progress in the field of self-healing biomaterials research by discussing both extrinsic and intrinsic self-healing systems. While the extrinsic self-healing section focuses on self-healing dental materials and orthopedic bone cements that rely on release of healing liquids from embedded microcapsules, the section on intrinsic self-healing materials mainly discusses concepts for self-healing of polymeric biomaterials that are either hydrated (hydrogels) or nonhydrated (e.g., films and coatings). Finally, benefits of the self-healing feature for biomaterials are discussed, and directions for future research and developments are outlined.