DataSheet1_Biocompatibility enhancement via post-processing of microporous scaffolds made by optical 3D printer.PDF

Providing a 3D environment that mimics the native extracellular matrix is becoming increasingly important for various applications such as cell function studies, regenerative medicine, and drug discovery. Among the most critical parameters to consider are the scaffold’s complicated micro-scale geometry and material properties. Therefore, stereolithography based on photopolymerization is an emerging technique because of its ability to selectively form volumetric structures from liquid resin through localized polymerization reactions. However, one of the most important parameters of the scaffold is biocompatibility, which depends not only on the material but also on the exposure conditions and post-processing, which is currently underestimated. To investigate this systematically, microporous scaffolds with pore sizes of 0.05 mm3 corresponding to a porosity of 16,4% were fabricated using the stereolithography printer Asiga PICO2 39 UV from the widely used resins FormLabs Clear and Flexible. The use of various polymers is usually limited for cells because, after wet chemical development, the non-negligible amount of remaining monomers intertwined in the photopolymerized structures is significantly toxic to cells. Therefore, the aim of this research was to find the best method to remove monomers from the 3D scaffold by additional UV exposure. For this purpose, a Soxhlet extractor was used for the first time, and the monomers were immersed in different alcohols. A Raman microspectroscopy was also used to investigate whether different post-processing methods affect DC (cross-linking) to find out if this specifically affects the biocompatibility of the scaffolds. Finally, mesenchymal stem cells from rat dental pulp were examined to confirm the increased biocompatibility of the scaffolds and their ability to support cell differentiation into bone tissue cells.构建能够模拟天然细胞外基质（extracellular matrix, ECM）的三维培养环境，在细胞功能研究、再生医学与药物研发等诸多领域的重要性与日俱增。该领域需重点考量的核心参数之一，是支架复杂的微观尺度几何结构与材料特性。基于光聚合（photopolymerization）原理的立体光刻（stereolithography）技术作为新兴工艺，可通过局部聚合反应从液态树脂中选择性制备三维立体结构，因此备受关注。然而，支架最为关键的性能参数之一为生物相容性（biocompatibility），其不仅取决于所用材料，还与曝光条件及后处理（post-processing）工艺密切相关，而这一点目前尚未得到足够重视。为系统探究该问题，研究团队采用市场广泛使用的FormLabs Clear与Flexible两款树脂，借助Asiga PICO2 39 UV型立体光刻打印机，制备了对应孔隙率16.4%、体积为0.05 mm³的微孔支架。但各类聚合物在细胞实验中的应用往往受限，原因在于湿化学显影（wet chemical development）后，光聚合结构中残留的不可忽略量的单体（monomers）对细胞具有显著毒性。为此，本研究旨在探索通过额外紫外曝光工艺去除三维支架中残留单体的最优方案。研究首次采用索氏提取器（Soxhlet extractor），将支架置于不同醇类溶剂中进行浸泡处理；同时借助拉曼显微光谱（Raman microspectroscopy）技术，探究不同后处理工艺对交联度（DC, cross-linking）的影响，以明确该变化是否会特异性影响支架的生物相容性。最后，通过大鼠牙髓间充质干细胞实验，研究验证了支架生物相容性的提升效果，以及其支持细胞向骨组织细胞分化的能力。