Self‐Healing Biomaterials: From Molecular Concepts to Clinical Applications

Abstract

were selected "off-the-shelf" based on the ingenuity of the surgeons. [1] During the last century, significant medical and technological progress has paved the way for the field of biomaterials research and the emergence of a biomaterials industry. Various synthetic or natural biomaterials have been developed which have enabled treatment of a wide range of medical conditions. Nevertheless, biomaterials are being considered for increasingly complex indications, which has increased the requirements for biomaterials considerably during the past decades. [2] Consequently, challenging-or even contradictorycombinations of biomaterial properties are often required which cannot be met by conventional biomaterials. For instance, biomaterials are desired which combine injectability, mechanical strength, and degradability with toughness to avoid mechanical damage following crack propagation. To meet these strict requirements, biomaterials are needed which can adapt to the implantation site and are able to heal themselves upon mechanical damage. While the majority of synthetic biomaterials does not recover from mechanical damage, natural tissues display a remarkable capacity for self-healing such as the spontaneous self-repair of bone fractures or ruptured skin. This self-healing ability is the ultimate solution of nature for continued survival based 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.

Dynamic cell–cell adhesion mediated by pericellular matrix interaction – a hypothesis

“…4A). This implies that self-adhesion and/or self-healing processes of polymer gels (Campanella et al, 2018;Diba et al, 2018) can serve as models for PCM adhesion.…”

“…Chain interdiffusion also allows to re-establish electrostatic, hydrophobic, hydrogen bond or metal coordination interactions that dynamically cross-link chains in the various gels (Fig. 4B) (Phadke et al, 2012;Stukalin et al, 2013;Campanella et al, 2018;Diba et al, 2018;Hinton et al, 2019;Cao and Forest, 2019). When left separated, free binding sites on fracture surfaces gradually recombine until an equilibrium is reached.…”

Self‐Healing Phenomena in Metals

“…Autonomous intrinsic healing in metals does not require the assistance of external (mechanical, thermal, electrical, or other energetic) input or triggers, but may require the lowering or complete removal of the forces responsible for the damage creation. These conditions are not different from those for other autonomous intrinsic healing materials such as polymers and natural bone . Also in these cases healing can take place at ambient temperatures, but the external mechanical load has to be removed temporarily to allow reformation of chemical and physical bonds across the damage site.…”

Self‐Healing Materials are Coming of Age

“…Collage of self‐healing materials addressed in the current Special Issue. Reproduced with permission …”