Bionic Self-Stimulated Cartilage

每年有数百万美国人因骨关节炎接受全膝关节置换术。手术 这种疾病的治疗是植入替代自体或同种异体移植物。尽管有许多优点，这些移植物 造成了几个限制，包括供应限制、供体部位发病率（对于自体移植物）和免疫反应 (in同种异体移植物）。因此，工程移植物-通过培养自体 软骨细胞的合成生物材料支架-已受到关注。然而，他们也表现出问题，其中之一， 这是这些移植物中的种子软骨细胞在植入后产生透明软骨的效率低下， 防止其广泛使用。因此，我们认为有必要寻求一种新的办法， 刺激和加速常用软骨细胞接种移植物的软骨生长， 愈合和再生能力。 电刺激（ES）已被证明对软骨和骨具有深远的影响 修复/再生。然而，当前的ES设备存在许多缺点，包括生成的能量的低效率。 电场（用于外部ES器械）、电刺激器中使用的体积庞大和有毒材料，以及非 植入ES器械的降解性。 压电材料可以通过变形产生电信号，反之亦然， 用来制造自供电的电刺激器有趣的是，聚-L-乳酸（PLLA），一种可生物降解的 聚合物已被用于许多医疗植入物，当被加工时可以表现出压电性 正常虽然不具有高压电常数，但PLLA由于其低介电参数而表现出 与普通聚偏二氟乙烯（PVDF）聚合物相同的能量转换效率。 在这个项目中，我们研究的科学和技术，以创造一个可生物降解，高效 压电PLLA刺激器并将该刺激器与生物软骨细胞接种的软骨移植物整合， 形成仿生软骨组织。假设，这种仿生软骨将创造一个反馈回路， 施加在软骨上的破坏性关节力将产生更多有用的电力，这反过来又增强了 软骨生长一旦在植入物上施加较小的力，移植物将受到较小的电刺激， 避免电流对软骨细胞的有害的过量效应。所产生的电输出-输入 对关节力的响应-可以通过改变PLLA膜的性质（例如厚度， 分子量、压电效率和PLLA层数等）。因此，这种“智能”仿生软骨 将提供一种创新的方法，优化电刺激软骨修复和再生， 自体软骨细胞移植物。

Millions of American go through total knee replacement every year due to osteoarthritis. Surgical treatment of this disease is to implant replacement auto or allografts. Despite many advantages, these grafts poses several limitations including limit of supplies, donor site morbidity (for autografts) and immune response (in case of allografts). Consequently, engineered grafts - constructed in vitro by culturing autologous chondrocytes on synthetic biomaterial scaffolds – have received attentions. Yet, they also exhibit issues, one of which is the inefficiency of seeded-chondrocytes in these grafts to generate hyaline cartilages after implantation, preventing their widespread use. As such, we believe it is necessary to seek for a new approach to effectively stimulate and accelerate cartilage growth from commonly-used chondrocyte-seeded grafts, enhancing the grafts’ healing and regeneration capability. Electrical stimulation (ES) have been shown to exhibit profound effects on cartilage and bone repair/regeneration. However, current ES devices present many drawbacks including inefficiency of generated electrical field (for external ES devices), bulky size and toxic materials used in electrical stimulators, and non- degradability of implanted ES devices. Piezoelectric materials, which can generate electrical signals from deformation and vice versa, can be employed to create self-powered electrical stimulators. Interestingly, Poly-L-Lactid acid (PLLA), a biodegradable polymer which has been used in many medical implants, can exhibit piezoelectricity when being processed properly. Although not having a high piezoelectric constant, PLLA, owing to its low dielectric parameter, exhibits the same efficiency for energy conversion as the common Polyvinylidene fluoride (PVDF) polymer. In this project, we study the science and technology to create a biodegradable, highly efficient piezoelectric PLLA stimulator and integrate the stimulator with a biological chondrocyte-seeded cartilage graft, forming a bionic cartilage tissue. Hypothetically, this bionic cartilage will create a feedback loop in which more damaging joint-forces imparted on the cartilage would generate more useful electricity, which in turn enhances cartilage growth. Once less force is exerted on the implant, the graft will be subject to less electrical stimulation, avoiding harmful overdosing effect of electrical current on cartilage cells. The generated electrical outputs – in response to joint force - can be tailored and optimized by altering PLLA film’s properties (e.g. thickness, molecular weight, piezoelectric efficiency and number of PLLA layers etc.). As such, this “smart” bionic cartilage will offer an innovative approach, optimizing electric stimulation for cartilage repair and regeneration from autologous chondrocyte-seeded grafts.