Geometry-controlled rigidity in non-spherical hydrogel capsules

非技术总结该项目的目标是创造具有几何控制刚度的中空微尺寸水凝胶颗粒（微胶囊），并提供对它们在压力下形状转变的基本理解。 颗粒的刚性和形状是决定特定生物功能的关键参数，控制它们可以全面优化胶囊的药物输送。 迄今为止，由于形状限定的水凝胶结构缺乏机械稳定性，通过改变其形状来调节水凝胶颗粒的刚性（刚度）已经提出了主要挑战。 本研究的关键任务是了解微胶囊的刚度如何通过结构特征（包括非球形曲率、边缘和小面的数量以及整体形状）来控制。 拟议的研究将影响复杂形状的微米级水凝胶的开发，这些水凝胶可以提供一种强大的手段来模拟生物系统的关键特性，并具有作为细胞模拟颗粒的潜力，可以开发成人工细胞和多功能递送载体。 这些胶囊的设计还提供了开发具有独特的致动特性的材料的前景，其在聚合物和材料科学、生物医学工程和化学生物学中具有应用。 该项目的教育目标是加强UAB的发现驱动的多学科聚合物科学计划，促进学生从高中到研究生阶段在化学，聚合物科学和材料科学的现代方面的培训，并扩大历史上代表性不足的人口的招聘。 这些努力还将有助于提高公众对纳米级聚合物材料的认识，并在东南部培训下一代STEM劳动力。 技术总结：本研究的目的是测试中空水凝胶微胶囊中几何形状控制刚度的假设，并在分子水平上获得对压力诱导的胶囊形状转变（屈曲）的基本理解。 目前的方法旨在主要通过选择聚合物、流体含量和交联密度来控制水凝胶颗粒的刚度。 拟议研究的目的是：（i）确定无垂直非球形胶囊中胶囊壁（壳）的物理化学性质如何影响压力诱导的形状转变;（ii）了解垂直增强胶囊中胶囊壳的物理化学性质如何影响压力诱导的形状转变;和（iii）发现如何通过多层水凝胶壳的内部结构控制胶囊壳的刚性。 将使用渗透压差法研究渗透压增加时由负体积变化（收缩和屈曲不稳定性）定义的尺寸和形状变化。 将研究交联密度、链持续长度、壳水合和结构对水凝胶稳定性的影响，以对抗渗透压诱导的屈曲（形状损失）和应力去除后的形状恢复。 几何控制的刚性和压力诱导的形状转变之间的基本关系将使用原位技术，包括原子力和共聚焦显微镜，椭圆偏振，纳米压痕，中子散射和ATR-FTIR的组合进行探索。 与UAB医学界的预期合作努力将为基础材料性能研究和生物医学应用测试材料性能之间的双向反馈提供宝贵的机会。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYThe goal of this project is to create hollow micro-sized hydrogel particles (microcapsules) with geometrically controlled rigidity and to provide fundamental understanding of their shape transformations under pressure. Particle rigidity and shape are crucial parameters that dictate specific biological functions, and controlling them could allow comprehensive optimization of capsules for delivery of medications. To date, regulating rigidity (stiffness) of hydrogel particles by varying their shapes has presented a major challenge due to the lack of mechanical stability of shape-defined hydrogel structures. The key task of this research is to understand how stiffness of microcapsules can be controlled by structural characteristics including non-spherical curvature, edge and facet number, and overall shape. The proposed research will impact the development of micro-sized hydrogels of complex shapes that can provide a powerful means to mimic key properties of biological systems and hold potential as cell-mimicking particles to be developed into artificial cells and multifunctional delivery carriers. The design of these capsules also offers prospects for developing materials with unique actuation characteristics having applications in polymer and materials science, biomedical engineering, and chemical biology. The educational objective of the project is to enhance a discovery-driven multidisciplinary polymer science program at UAB, to promote student training from the high school through graduate-level in modern aspects of chemistry, polymer science, and materials science, and to broaden recruitment of historically underrepresented populations. These efforts will also help to increase public awareness of nanoscale polymeric materials and to train the next generation of the STEM workforce in the southeast. TECHNICAL SUMMARY:The goal of this research is to test the hypothesis of geometry-controlled rigidity in hollow hydrogel microcapsules and to gain fundamental understanding of pressure-induced capsule shape transitions (buckling) at a molecular-level. Current approaches aim to control the stiffness of hydrogel particles mainly by choice of polymer, fluid content, and crosslink density. The objectives of the proposed study are: (i) to determine how pressure-induced shape transformations are affected by physicochemical properties of the capsule wall (shell) in vertices-free non-spherical capsules; (ii) to understand how pressure-induced shape transitions are influenced by the physicochemical properties of the capsule shell in vertices-reinforced capsules; and (iii) to discover how capsule shell rigidity can be controlled via the internal structure of the multilayer hydrogel shell. Dimensional and shape changes defined by negative volume changes (shrinkage and buckling instability) in response to increasing osmotic pressure will be investigated using an osmotic pressure difference method. The impacts of crosslink density, chain persistence length, shell hydration and architecture on the hydrogel stability against osmotic pressure-induced buckling (shape loss) and shape recovery after stress removal will be studied. The fundamental relationships between the geometry-controlled rigidity and pressure-induced shape transitions will be explored using a combination of in-situ techniques including atomic force and confocal microscopy, ellipsometry, nanoindentation, neutron scattering, and ATR-FTIR. The expected collaborative effort with the UAB medical community will provide valuable opportunities for two-way feedback between the research on fundamental material properties and testing materials performance for biomedical applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.