COMPOSITE MATRICES BY 3D PRINTING AND BIOMIMETIC PROCESS

为了结合陶瓷的骨传导性能和聚合物的机械弹性，人们提出了将陶瓷和可吸收聚合物组成的复合基质作为骨再生的支架材料。“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。即使是非骨传导聚合物的磷灰石涂层也极大地提高了骨的传导性。虽然这种磷灰石涂层技术已被广泛报道或聚合物，但大多数已发表的结果涉及简单的，无孔衬底。在厚(&gt；1厘米)多孔聚合物结构中形成均匀的磷灰石涂层尚未见报道。与非多孔基质相比，多孔支架的表面积与体积比要高得多，而满足较大表面积的离子在临床相关尺寸的厚支架(&gt；1厘米)中的传输可能是受限的。我们假设，通过影响基本离子的成核和生长的可用性，运输限制控制着磷灰石成核和生长在大型、复杂(&gt；1厘米)组织工程支架的相互连接的孔隙中的动力学和分布。这一假设将通过控制几个直接影响传输行为的相关参数(流体流量、传输长度-尺度和流动阻力)来进行实验验证。流体流量控制每单位时间内离子的可获得性，并可通过调节泵速轻松控制。传输长度-尺度决定了离子传输的空间均匀性，并且可以通过在厚支架上结合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。较小的气孔导致较大的流动阻力，并产生较大的表面积。具有不同通道直径和微孔率的多孔多通道器件将通过一种新的基于计算机的制造技术来构建，该技术已成功地用于制造具有复杂宏观形状(&gt；1 cm)、定向通道(&lt；1 cm)和相互连接的孔隙率(0.01-0.1 mm)的大型聚合物支架。样品将经受不同的传输条件，在特定的关键位置进行切片，并对其进行微观结构和化学表征，以确定传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.