磷酸钙相组成对类骨单位复合骨支架的影响

从组成上看, 自然骨是一种无机与有机的复合材料; 从结构上看, 致密骨的基本结构单位为内壁血管化的骨单位。本研究基于组成与结构仿生的原理制备组织工程化支架, 模拟具有复杂结构的密质骨的基本单位——骨单位。为此, 通过静电纺丝和双螺杆挤出相结合的两步制造法, 制备一种具有双层结构的聚己内酯/磷酸钙(PCL/CaP)复合骨支架, 其内层是由电纺纳米纤维组成的空心管, 可贴附内皮细胞层形成与哈佛氏管相类似的结构; 其外层是具有高孔隙率的螺旋状PCL/CaP微丝, 可复合前成骨细胞以模拟骨单位结构中的外层骨样组织。为进一步探索材料组成对于支架生物功能的影响, 分别设计了外层为PCL, PCL/双相磷酸钙(PCL/BCP)和PCL/β-磷酸三钙(PCL/β-TCP)的复合支架, 比较了材料组分变化对外层微丝结构及前成骨细胞(MC3T3-E1)活性的影响。相比于PCL和PCL/β-TCP, PCL/BCP微丝更能显著增强细胞的生长和钙的沉积, 并成功获得可精确调控不同细胞的空间分布的双层复合支架, 实现对复杂结构骨单位的模拟构建, 显示出很好的应用前景。

Effect of Phase Composition of Calcium Phosphate (CaP) on Bioactivity of Osteon-like Composite Scaffolds

From compositional perspective, natural bone is a kind of inorganic and organic composite material; while from structural perspective, the basic structural unit of cortical bone is vascularized osteon. In this study, based on the biomimetic principle, a tissue-engineered construct was created to stimulate the basic building block of cortical bone-osteon with complex structure. To achieve this goal, a bi-layered polycaprolactone (PCL)/CaP composite scaffold was produced via a novel two-step fabrication process in the combination of electrospinning and twin screw extrusion. Its inner hollow tube was made of electrospun nanofibers, allowing the formation of a confluent layer of endothelial cells (MS-1) to resemble the Haversian canal, and its outer layer consisted of spiral PCL/CaP microfilament with high porosity, facilitating the proliferation and differentiation of pre-osteoblasts (MC3T3-E1) to form bone-like tissues. To explore the effect of material composition on scaffold bioactivity, three composite scaffolds with different outer layers were fabricated, including PCL, PCL/biphasic calcium phosphate (BCP) and PCL/β-tricaclium phosphate (β-TCP). And then the influences of scaffold composition on the behaviors of pre-osteoblasts were further investigated. Compared to PCL and PCL/β-TCP, significantly more cell growth and higher calcium deposition are found on PCL/BCP scaffolds, precisely controlling the spatial distribution of different cells. Taken together, this bi-layered PCL/BCP scaffold partially mimics the complex structure of osteon, showing a promising potential in the orthopedic application.