Piezoelectric Biocomposites for Bone Grafting in Dentistry

Multifunctional piezoelectric hydrogels under ultrasound stimulation boost chondrogenesis by recruiting autologous stem cells and activating the Ca2+/CaM/CaN signaling pathway

Articular cartilage, owing to the lack of undifferentiated stem cells after injury, faces significant challenges in reconstruction and repair, making it a major clinical challenge. Therefore, there is an urgent need to design a multifunctional hydrogels capable of recruiting autologous stem cells to achieve in situ cartilage regeneration. Here, our study investigated the potential of a piezoelectric hydrogel (Hyd6) for enhancing cartilage regeneration through ultrasound (US) stimulation. Hyd6 has multiple properties including injectability, self-healing capabilities, and piezoelectric characteristics. These properties synergistically promote stem cell chondrogenesis. The fabrication and characterization of Hyd6 revealed its excellent biocompatibility, biodegradability, and electromechanical conversion capabilities. In vitro and in vivo experiments revealed that Hyd6, when combined with US stimulation, significantly promotes the recruitment of autologous stem cells and enhances chondrogenesis by generating electrical signals that promote the influx of Ca2+, activating downstream CaM/CaN signaling pathways and accelerating cartilage formation. An in vivo study in a rabbit model of chondral defects revealed that Hyd6 combined with US treatment significantly improved cartilage regeneration, as evidenced by better integration of the regenerated tissue with the surrounding cartilage, greater collagen type II expression, and improved mechanical properties. The results highlight the potential of Hyd6 as a novel therapeutic approach for treating cartilage injuries, offering a self-powered, noninvasive, and effective strategy for tissue engineering and regenerative medicine.

Nanomaterial-based scaffolds for bone regeneration with piezoelectric properties

For proper cellular growth, to prepare tissue scaffold mimicking the tissue properties is a significant challenge. Bone is a vital organ supporting the whole human body for its function. The efficiencies in its structure for a variety of reasons should properly be remedied. Bone tissue engineering (BTE) is an emerging field addressing to develop or repair bone tissue for its proper function. The bone is naturally a piezoelectric material and generates electrical stimuli because of mechanical stress. Thus, the use of piezoelectric materials to build bone tissue is of great interest in BTE. Both piezoelectric polymers and nanomaterials (NMs) are investigated for this goal. In this review, we give an overview of the recent advances in piezoelectric NMs to construct piezoelectric scaffolds in BTE.

Biomimetic piezoelectric hydrogel system for energy metabolism reprogramming in spinal cord injury repair

Rationale: Spinal cord injury (SCI) leads to limited regenerative capacity and severe energy deficiency in the injury microenvironment. This study aimed to develop a biomimetic piezoelectric hydrogel system that could recapitulate the native tissue microenvironment while enabling wireless physical regulation for SCI repair. Methods: A piezoelectric hydrogel was fabricated by integrating K0.5Na0.5NbO3 (KNN) nanoparticles with porous decellularized spinal cord matrix gel (pDG). The hydrogel's effects on vascular endothelial cell migration, neural stem cell differentiation, and ATP synthesis were evaluated in vitro. RNA sequencing was performed to identify key regulatory pathways. The therapeutic efficacy was assessed in a rat model of spinal cord hemisection, examining motor function and angiogenesis. Results: The piezoelectric hydrogel demonstrated excellent biocompatibility and significantly enhanced vascular endothelial cell and neural cell migration. Under ultrasonic stimulation, the hydrogel promoted neural stem cell differentiation into neurons more effectively than control hydrogels. The piezoelectric stimulation increased ATP synthesis and calcium ion flux, activating the Ca2+/Camk2b/PGC-1α signaling axis. In vivo studies showed that implantation of the piezoelectric hydrogel combined with ultrasound stimulation significantly improved motor function recovery and promoted angiogenesis. Conclusion: The piezoelectric hydrogel system presents an effective strategy for SCI repair through energy metabolism reprogramming and demonstrates promising potential in neural tissue engineering applications.

Piezoelectric Biomaterial with Advanced Design for Tissue Infection Repair

Bacterial infection has become the most dangerous factor in tissue repair, which strongly affects the tissue regeneration efficiency and wellness of patients. Piezoelectric materials exhibit the outstanding advantage of producing electrons without external power supply. The ability of electron enrichment and reactive oxygen species generation through noninvasive stimulations enables piezoelectric materials the potential applications of antibacterial. Many studies have proved the feasibility of piezoelectric materials as a functional addition in antibacterial biomaterial. In fact, numerous piezoelectric materials with ingenious designs are reported to be effective in antibacterial processes. This review summarizes the antibacterial mechanisms of piezoelectric, illuminating their potential in combating bacteria. Recent advancement in the design and construction of piezoelectric biomaterial including defect engineering, heterojunction, synergy with metal and the composite scaffold configuration are thoroughly reviewed. Moreover, the applications and therapeutic effects of piezoelectric materials in common tissues with antibacterial requirements are introduced, such as orthopedics, dental, and wound healing. Finally, the development prospects and points deserving further exploration are listed. This review is expected to provide valuable insight into the relationship between antibacterial processes and piezoelectric materials, further inspiring constructive development in this emerging scientific discipline.

Advanced Piezoelectric Materials, Devices, and Systems for Orthopedic Medicine

Harnessing the robust electromechanical couplings, piezoelectric materials not only enable efficient bio-energy harvesting, physiological sensing and actuating but also open enormous opportunities for therapeutic treatments through surface polarization directly interacting with electroactive cells, tissues, and organs. Known for its highly oriented and hierarchical structure, collagen in natural bones produces local electrical signals to stimulate osteoblasts and promote bone formation, inspiring the application of piezoelectric materials in orthopedic medicine. Recent studies showed that piezoelectricity can impact microenvironments by regulating molecular sensors including ion channels, cytoskeletal elements, cell adhesion proteins, and other signaling pathways. This review thus focuses on discussing the pioneering applications of piezoelectricity in the diagnosis and treatment of orthopedic diseases, aiming to offer valuable insights for advancing next-generation medical technologies. Beginning with an introduction to the principles of piezoelectricity and various piezoelectric materials, this review paper delves into the mechanisms through which piezoelectric materials accelerated osteogenesis. A comprehensive overview of piezoelectric materials, devices, and systems enhancing bone tissue repair, alleviating inflammation at infection sites, and monitoring bone health is then provided, respectively. Finally, the major challenges faced by applications of piezoelectricity in orthopedic conditions are thoroughly discussed, along with a critical outlook on future development trends.

Piezoelectric Hydrogels: Hybrid Material Design, Properties, and Biomedical Applications

Hydrogels show great potential in biomedical applications due to their inherent biocompatibility, high water content, and resemblance to the extracellular matrix. However, they lack self-powering capabilities and often necessitate external stimulation to initiate cell regenerative processes. In contrast, piezoelectric materials offer self-powering potential but tend to compromise flexibility. To address this, creating a novel hybrid biomaterial of piezoelectric hydrogels (PHs), which combines the advantageous properties of both materials, offers a systematic solution to the challenges faced by these materials when employed separately. Such innovative material system is expected to broaden the horizons of biomedical applications, such as piezocatalytic medicinal and health monitoring applications, showcasing its adaptability by endowing hydrogels with piezoelectric properties. Unique functionalities, like enabling self-powered capabilities and inducing electrical stimulation that mimics endogenous bioelectricity, can be achieved while retaining hydrogel matrix advantages. Given the limited reported literature on PHs, here recent strategies concerning material design and fabrication, essential properties, and distinctive applications are systematically discussed. The review is concluded by providing perspectives on the remaining challenges and the future outlook for PHs in the biomedical field. As PHs emerge as a rising star, a comprehensive exploration of their potential offers insights into the new hybrid biomaterials.