Piezoelectric scaffold for tissue engineering: material, structure, fabrication and function

The scaffold for tissue engineering not only requires good biocompatibility, mechanical properties, and appropriate structure, but also should actively participate in biophysical and biochemical processes to accelerate tissue repair. A piezoelectric scaffold can generate electrical activity when deformed, which constructs an electrochemical microenvironment for inducing cell signaling pathways and facilitating tissue regeneration, attracting extensive attention in tissue engineering. Herein, piezoelectric materials used in tissue engineering, including piezoelectric ceramics, synthetic piezoelectric polymers, and natural biological piezoelectric materials are systematically summarized, and their advantages and limitations are analyzed. As for the piezoelectric scaffold, the piezoelectric properties mainly stem from the asymmetric crystal structure of materials and the directional arrangement of internal dipoles, which is highly dependent on the fabrication and post-treatment strategies. Therefore, the fabrication techniques of piezoelectric scaffold are detailly introduced, covering both traditional fabrication techniques and additive manufacturing techniques. Besides, rational structural design of the piezoelectric scaffold can alter strain transmission pathways and charge distribution, or add new operational modes to regulate piezoelectric properties. Thereby, the piezoelectric metamaterials, micro/nanostructures, porous structures, heterogeneous structures, and biomimetic structures are comprehensively summarized. Additionally, the functions of piezoelectric scaffold for tissue engineering application in terms of bone regeneration, neural regeneration, antibacterial activity, and intelligent sensing are reviewed. Finally, the challenges and future research directions of the piezoelectric scaffold are discussed.