Department of Materials Science and Engineering and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware 19716, USA.
Langmuir. 2012 Apr 10;28(14):6076-87. doi: 10.1021/la2041746. Epub 2012 Mar 27.
β-hairpin peptide-based hydrogels are a class of injectable solid hydrogels that can deliver encapsulated cells or molecular therapies to a target site via syringe or catheter injection as a carrier material. These physical hydrogels can shear-thin and consequently flow as a low-viscosity material under a sufficient shear stress but immediately recover back into a solid upon removal of the stress, allowing them to be injected as preformed gel solids. Hydrogel behavior during flow was studied in a cylindrical capillary geometry that mimicked the actual situation of injection through a syringe needle in order to quantify effects of shear-thin injection delivery on hydrogel flow behavior and encapsulated cell payloads. It was observed that all β-hairpin peptide hydrogels investigated displayed a promising flow profile for injectable cell delivery: a central wide plug flow region where gel material and cell payloads experienced little or no shear rate, and a narrow shear zone close to the capillary wall where gel and cells were subject to shear deformation. The width of the plug flow region was found to be weakly dependent on hydrogel rigidity and flow rate. Live-dead assays were performed on encapsulated MG63 cells 3 h after injection flow and revealed that shear-thin delivery through the capillary had little impact on cell viability and the spatial distribution of encapsulated cell payloads. These observations help us to fundamentally understand how the gels flow during injection through a thin catheter and how they immediately restore mechanically and morphologically relative to preflow, static gels.
β-发夹肽水凝胶是一类可注射的固体水凝胶，可作为载体材料，通过注射器或导管注射将封装的细胞或分子疗法递送到靶位。这些物理水凝胶可以在足够的剪切应力下剪切变稀，从而作为低粘度材料流动，但在去除应力后立即恢复为固体，从而允许它们作为预成型的凝胶固体进行注射。在圆柱形毛细管几何形状中研究了水凝胶在流动过程中的行为，该几何形状模拟了通过注射器针头实际注射的情况，以便量化剪切变稀注射输送对水凝胶流动行为和封装细胞载药量的影响。观察到所有研究的β-发夹肽水凝胶都显示出用于可注射细胞递送的有前途的流动特性：凝胶材料和细胞载药量经历很少或没有剪切速率的中央宽塞流区域，以及靠近毛细管壁的狭窄剪切区域，其中凝胶和细胞受到剪切变形。塞流区域的宽度发现与水凝胶的刚性和流速弱相关。在注射流动后 3 小时对封装的 MG63 细胞进行活/死检测，结果表明，通过毛细管的剪切变稀输送对细胞活力和封装细胞载药量的空间分布几乎没有影响。这些观察结果帮助我们从根本上了解凝胶在通过细导管注射过程中的流动方式，以及它们相对于预流动、静态凝胶如何立即在机械和形态上恢复。
