Recent progress of 3D printed responsive scaffolds for bone repair: A review

Bone defects are complex in etiology, extensive in scope, and associated with local microenvironmental disruption, leading to issues such as donor site complications, poor biocompatibility, and inadequate functional recovery with traditional treatment methods (e.g., autologous bone transplantation, metal implants). Bone repair scaffolds have garnered widespread attention due to their excellent biomimetic properties and high repair efficiency. With the advantages of personalization, high-precision manufacturing and complex structure forming, 3D printing technology has shown great potential for application in the field of bone restoration. In contrast to conventional bone scaffolds, responsive scaffolds emulate the dynamic environment of the natural extracellular matrix, which can produce controlled effects in responding to stimuli, hence promoting cell multiplication and differentiation and bone regeneration. This review introduces the study of human bone structure and defects, summarizes the 3D printing technologies of preparing bone scaffolds, concludes the characteristics and applicability of different 3D printing technologies, then the applications of light, piezoelectric, temperature, immune, magnetic, and enzyme-responsive scaffolds in the field of bone repair are summarized according to the types of responses of bone scaffolds to various types of stimuli in the human body, and finally the problems faced by responsive scaffolds in the process of clinical translation are pointed out.