Extrusion-based 3D printing of poly(propylene fumarate) scaffolds with hydroxyapatite gradients.

The primary focus of this work is to present the current challenges of printing scaffolds with concentration gradients of nanoparticles with an aim to improve the processing of these scaffolds. Furthermore, we address how print fidelity is related to material composition and emphasize the importance of considering this relationship when developing complex scaffolds for bone implants. The ability to create complex tissues is becoming increasingly relevant in the tissue engineering community. For bone tissue engineering applications, this work demonstrates the ability to use extrusion-based printing techniques to control the spatial deposition of hydroxyapatite (HA) nanoparticles in a 3D composite scaffold. In doing so, we combined the benefits of synthetic, degradable polymers, such as poly(propylene fumarate) (PPF), with osteoconductive HA nanoparticles that provide robust compressive mechanical properties. Furthermore, the final 3D printed scaffolds consisted of well-defined layers with interconnected pores, two critical features for a successful bone implant. To demonstrate a controlled gradient of HA, thermogravimetric analysis was carried out to quantify HA on a per-layer basis. Moreover, we non-destructively evaluated the tendency of HA particles to aggregate within PPF using micro-computed tomography (µCT). This work provides insight for proper fabrication and characterization of composite scaffolds containing particle gradients and has broad applicability for future efforts in fabricating complex scaffolds for tissue engineering applications.

这项工作的主要重点是呈现纳米粒子浓度梯度打印支架目前面临的挑战，目的是改进这些支架的加工工艺。此外，我们阐述了打印保真度如何与材料成分相关，并强调在开发用于骨植入物的复杂支架时考虑这种关系的重要性。在组织工程领域，制造复杂组织的能力变得越来越重要。对于骨组织工程应用，这项工作展示了利用基于挤出的打印技术来控制羟基磷灰石（HA）纳米粒子在三维复合支架中的空间沉积的能力。在此过程中，我们将合成的可降解聚合物（如聚富马酸丙二醇酯（PPF））的优点与提供强大压缩力学性能的骨传导性HA纳米粒子相结合。此外，最终的3D打印支架由具有相互连通孔隙的明确分层组成，这是成功的骨植入物的两个关键特征。为了展示HA的可控梯度，进行了热重分析，以逐层量化HA。此外，我们使用微计算机断层扫描（µCT）无损地评估了HA粒子在PPF内聚集的趋势。这项工作为正确制造和表征含有粒子梯度的复合支架提供了见解，并对未来制造用于组织工程应用的复杂支架的工作具有广泛的适用性。