COMPOSITE MATRICES BY 3D PRINTING AND BIOMIMETIC PROCESS

为了结合陶瓷的导骨性能和聚合物的机械弹性，提出了含陶瓷和可吸收聚合物的复合基质作为骨再生支架材料。“仿生”矿化涉及磷灰石晶体在过饱和离子环境中的成核和生长。磷灰石涂层即使是固有的非骨导电性聚合物也大大提高了骨导电性。尽管这种磷灰石涂层技术已被广泛报道，但大多数已发表的结果涉及简单的，无孔的基底。在厚的多孔聚合物结构中形成均匀的磷灰石涂层尚未见报道。多孔支架比非多孔支架具有更高的表面体积比，并且在临床相关尺寸的厚支架（bbb10 - 1cm）中，满足大表面积的离子输送可能受到运输限制。我们假设，通过影响成核和生长必需离子的可用性，运输限制控制了磷灰石在大型复杂组织工程支架（bbb1cm）相互连接的孔隙中成核和生长的动力学和分布。这一假设将通过控制几个直接影响输运行为的相关参数（流体流速、输运长度尺度和流动阻力）进行实验验证。流体流速控制着单位时间内离子的可用性，并且很容易通过调节泵的转速来控制。输送长度尺度决定了离子输送的空间均匀性，并且可以通过在整个厚支架中加入不同尺寸的通道来控制。流动阻力可以通过改变孔径来控制。较小的孔隙导致较大的流动阻力，也产生较大的表面积。具有不同通道直径和微孔隙度的多孔多通道器件将由一种新的基于计算机的制造技术构建，该技术已成功地用于制造具有复杂宏观形状（bbb1cm），定向通道（< 1cm）和互连孔隙度（0.01 - 0.1 mm）的大型聚合物支架。样品将经受各种运输条件，在指定的战略位置切片，并表征微观结构和化学，以确定运输参数对涂层均匀性的影响。

Composite matrices containing ceramics and absorbable polymers have been proposed as scaffolding materials for bone regeneration in order to combine the osteoconductive properties of the ceramics and the mechanical resiliency of the polymers. "Biomimetic" mineralization involves the nucleation and growth of apatite crystals in a super-saturated ionic environment. Apatite coating of even inherently non-osteoconductive polymers have greatly improved osteoconductivity. Although this apatite- coating technique has been reported with a wide range or polymers, most of the published results involve simple, non-porous substrates. The creation of uniform apatite coating throughout thick (>1 cm) porous polymeric structures has not been reported. Porous scaffolds involve much higher surface-to-volume ratios than non-porous substrates, and the delivery of ions to satisfy the large surface area may be transport-limited in thick scaffolds (>1 cm) of clinically relevant dimensions. We hypothesized that by affecting the availability of essential ions for nucleation and growth, transport limitations govern the kinetics and distribution of apatite nucleation and growth within the interconnected pores of large, complex (>1 cm) tissue engineering scaffolds. This hypothesis will be tested experimentally by controlling several relevant parameters (fluid flow rate, transport length-scale, and resistance to flow) that directly affect transport behavior. Fluid flow rate controls the availability of ions per unit time, and is easily controlled by adjusting the pump speed. Transport length-scale determines the spatial uniformity of ionic delivery, and can be controlled by incorporating channels of varying dimensions throughout the thick scaffolds. Flow resistance can be controlled by varying pore size. Smaller pores result in larger flow resistance, and also produce larger surface areas. Porous multichannel devices with varying channel diameter and microporosity will be constructed by a novel computer-based manufacturing technology, which 'has been used successfully to fabricate large polymeric scaffolds possessing complex macroscopic shape (>1 cm), oriented channels (<1 cm), and interconnected porosity (0.01 - 0.1 mm). Samples will be subjected to various transport conditions, sectioned at specified strategic locations, and characterized microstructurally and chemically to determine the effects of transport parameters on coating uniformity.