Ultrasound-responsive smart composite biomaterials in tissue repair

Tissue repair is a cascade of sequential biological events initiated to repair damages inflicted by trauma, pathogenic bacteria, or other injury-causing factors, with the aim of restoring tissue integrity. Smart composite biomaterials are able to react to biological signals released after tissue damages and make adjustments that suit the dynamic and complex internal environment based on external information, thus maintaining the homeostasis of the internal environment in the human body. Ultrasound is considered as an excellent "remote control" and "trigger" for smart composite biomaterials due to its basic technical characteristic effects that primarily include cavitation, microstreaming, scattering, and acoustic radiation force. Here, we presented the first comprehensive and systematic review of the research progress of ultrasound-responsive smart composite biomaterials in tissue repair. In this review, firstly, we elaborated on the definition and mechanism of ultrasound, followed by a brief analysis of the principles of the response of biomaterials to ultrasound. Then, to systematically review the subject, we divide ultrasound-responsive smart composite biomaterials into following categories: anti-infective, skin repair, osteogenic, gene transfection, thrombolytic, neuromuscular, and imaging. Finally, there is a brief summary of ultrasound-responsive smart composite biomaterials, and an outlook based on characteristics of physiological repair of tissues in each system.