Department of Bioengineering, University of California Los Angeles, 410 Westwood Plaza, 5121 Engineering V, Los Angeles, California 90095, United States.
ACS Appl Mater Interfaces. 2021 Feb 10;13(5):5929-5944. doi: 10.1021/acsami.0c19627. Epub 2021 Jan 27.
Cross-linked polyacrylamide hydrogels are commonly used in biotechnology and cell culture applications due to advantageous properties, such as the precise control of material stiffness and the attachment of cell adhesive ligands. However, the chemical and physical properties of polyacrylamide gels cannot be altered once fabricated. Here, we develop a photodegradable polyacrylamide gel system that allows for a dynamic control of polyacrylamide gel stiffness with exposure to light. Photodegradable polyacrylamide hydrogel networks are produced by copolymerizing acrylamide and a photocleavable -nitrobenzyl (-NB) bis-acrylate cross-linker. When the hydrogels are exposed to light, the -NB cross-links cleave and the stiffness of the photodegradable polyacrylamide gels decreases. Further examination of the effect of dynamic stiffness changes on cell behavior reveals that softening of the culture substrate leads to changes in cell behavior that are not observed when cells are cultured on presoftened gels, indicating that both dynamic and static mechanical environments influence cell fate. Notably, we observe significant changes in nuclear localization of YAP and cytoskeletal organization after softening; these changes further depend on the type and concentration of cell adhesive proteins attached to the gel surface. By incorporating the simplicity and well-established protocols of standard polyacrylamide gel fabrication with the dynamic control of photodegradable systems, we can enhance the capability of polyacrylamide gels, thereby enabling cell biologists and engineers to study more complex cellular behaviors that were previously inaccessible using regular polyacrylamide gels.
交联聚丙烯酰胺水凝胶由于具有有利的性质，例如对材料硬度的精确控制和细胞黏附配体的附着，因此常用于生物技术和细胞培养应用中。然而，一旦制造完成，聚丙烯酰胺凝胶的化学和物理性质就无法改变。在这里，我们开发了一种光降解的聚丙烯酰胺凝胶系统，该系统可以通过暴露于光来动态控制聚丙烯酰胺凝胶的硬度。光降解的聚丙烯酰胺水凝胶网络是通过丙烯酰胺和光可裂解的 -硝基苄基（-NB）双丙烯酰胺交联剂共聚而产生的。当水凝胶暴露于光时，-NB 交联会断裂，光降解的聚丙烯酰胺凝胶的硬度会降低。进一步研究动态硬度变化对细胞行为的影响表明，培养基质的软化会导致细胞行为发生变化，而这些变化在细胞培养于预先软化的凝胶上时不会观察到，这表明动态和静态机械环境都会影响细胞命运。值得注意的是，我们观察到在软化后 YAP 的核定位和细胞骨架组织发生了显著变化；这些变化进一步取决于附着在凝胶表面的细胞黏附蛋白的类型和浓度。通过将标准聚丙烯酰胺凝胶制造的简单性和成熟的方案与光降解系统的动态控制相结合，我们可以增强聚丙烯酰胺凝胶的能力，从而使细胞生物学家和工程师能够研究以前使用常规聚丙烯酰胺凝胶无法研究的更复杂的细胞行为。
