Modular injectable scaffolds for cell therapy and 3D bioprinting

目前的研究计划旨在开发生物材料支架作为工程工具，以提高细胞治疗的疗效。细胞疗法包括将细胞移植到患者体内，可用于治疗许多疾病或修复组织。然而，注射的细胞迅速染色或从组织中冲洗出来。水凝胶支架中的细胞包封具有通过提高细胞活力和在递送部位的保留来改善细胞治疗结果的潜力，但理想的支架仍然缺失。此外，影响细胞存活和向靶组织迁移的能力的支架参数仍然知之甚少。 近年来，候选人一直在开发可生物降解的原位凝胶化水凝胶，具有增强的机械性能和优异的细胞相容性。当在室温下仍为液体时，可以将细胞混合到预水凝胶溶液中，并通过针或导管注射。在体内迅速形成粘性凝胶。本项目旨在进一步改善这些可注射的细胞载体，即通过改善细胞微环境，促进氧气扩散到细胞并增加其对靶组织的粘附。 主要方法包括：1）将细胞外基质化合物掺入水凝胶中，以更好地再现正常的细胞-组织相互作用; 2）使用可快速生物降解的微球开发空隙形成（大孔）支架;以及3）以可在体内自组装的微球形式制造细胞载体。我们假设，与大体积水凝胶中的包封相比，微球中的包封将改善氧向细胞的扩散，促进细胞逃逸，并最终促进血管网络的形成，从而为细胞提供氧和营养。我们还将优化微囊化过程，使内皮细胞粘附在表面上，从而加速可灌注血管网络的形成。 此外，我们将优化这些可注射水凝胶作为3D生物打印的生物墨水。这种增材制造工艺允许形成具有受控异质性和个性化几何形状的组织样结构，其可用作3D体外模型或可植入支架。然而，只有少数生物墨水是可用的，其中大多数是基于不可生物降解的藻酸盐。在这个项目中，我们将提出基于壳聚糖-甲基丙烯酸明胶互穿网络的新型生物墨水。 这些新的可注射模块化细胞载体将为细胞治疗和3D模型的形成提供许多机会，并将为影响细胞治疗细胞载体成功的因素带来重要知识。最后一个好处是在生物材料科学，流变学，机械工程和生物学之间的前沿这一重要领域培养高质量，高素质的人才（HQP）。

The present research program aims to develop biomaterials scaffolds as engineering tools to improve the efficacy of cell therapy. Cell therapy consists in the transplantation of cells into patients and can be used to treat many diseases or repair tissues. However injected cells dye rapidly or are flushed from the tissue. Cell encapsulation in hydrogel scaffolds has the potential to improve cell therapy outcomes by enhancing cell viability and retention at the delivery site, but ideal scaffold are still missing. Moreover, the scaffold parameters that influence the survival and ability of cells to migrate towards the targeted tissue are still poorly understood. In the recent years, the candidate has been developing biodegradable in situ gelling hydrogels with enhanced mechanical properties and excellent cytocompatibility. Cells can be mixed to the pre-hydrogel solution when still liquid at room temperature and injected by needle or catheter. A cohesive gel rapidly form in vivo. The present project aims to further improve these injectable cell carriers, namely by improving cell microenvironment, facilitating oxygen diffusion to the cells and increasing their adhesion to the target tissues. The main approaches will consist in 1) the incorporation of extracellular matrix compounds into hydrogels to better reproduce normal cell-tissue interactions 2) the development of void-forming (macroporous) scaffolds using rapidly biodegradable microspheres, and 3) the fabrication of cell-carriers in the form of microspheres that can self-assemble in vivo. We hypothesize that compared to encapsulation in large hydrogel volumes, encapsulation in microspheres will improve oxygen diffusion to the cells, facilitate cell escape and eventually promote formation of blood vessel network that will provide oxygen and nutrients to the cells. We will also optimize the microencapsulation process to allow endothelial cells adhesion on the surface and thus accelerate the formation of a perfusable vascular network. In addition, we will optimize these injectable hydrogels as bioinks for 3D bioprinting. This additive manufacturing process allows to form tissue-like structures with controlled heterogeneity and personalized geometry, which can be used as 3D in vitro models, or as implantable scaffolds. However only a few bioinks are available and most of them are based on the non-biodegradable alginate. In this project, we will propose new bioinks based on chitosan- methacrylated gelatin interpenetrating networks. These new injectable modular cell carriers will offer many opportunities as tools for cell therapy and formation of 3D models and will bring significant knowledge on the factors influencing the success of cell carrier for cell therapy. A final benefit is the training of high-quality, highly qualified personnel (HQP) in this important field at the frontier between biomaterials science, rheology, mechanical engineering and biology.