School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K.
School of Computing, University of Leeds, Leeds LS2 9JT, U.K.
Biomacromolecules. 2020 Oct 12;21(10):4253-4260. doi: 10.1021/acs.biomac.0c01044. Epub 2020 Sep 25.
Hydrogels constructed from folded protein domains are of increasing interest as resilient and responsive biomaterials, but their optimization for applications requires time-consuming and costly molecular design. Here, we explore a complementary approach to control their properties by examining the influence of crosslinking rate on the structure and viscoelastic response of a model hydrogel constructed from photochemically crosslinked bovine serum albumin (BSA). Gelation is observed to follow a heterogeneous nucleation pathway in which BSA monomers crosslink into compact nuclei that grow into fractal percolated networks. Both the viscoelastic response probed by shear rheology and the nanostructure probed by small-angle X-ray scattering (SAXS) are shown to depend on the photochemical crosslinking reaction rate, with increased reaction rates corresponding to higher viscoelastic moduli, lower fractal dimension, and higher fractal cluster size. Reaction rate-dependent changes are shown to be consistent with a transition between diffusion- and rate-limited assembly, and the corresponding changes to viscoelastic response are proposed to arise from the presence of nonfractal depletion regions, as confirmed by SAXS. This controllable nanostructure and viscoelasticity constitute a potential route for the precise control of hydrogel properties, without the need for molecular modification.
由折叠蛋白结构域构建的水凝胶作为有弹性和响应性的生物材料越来越受到关注，但为了应用而对其进行优化需要耗时且昂贵的分子设计。在这里，我们通过研究光化学交联牛血清白蛋白（BSA）构建的模型水凝胶的交联速率对其结构和粘弹性响应的影响，探索了一种控制其性能的互补方法。胶凝被观察到遵循非均相成核途径，其中 BSA 单体交联成紧凑的核，这些核生长成分形渗透网络。剪切流变学探测的粘弹性响应和小角 X 射线散射（SAXS）探测的纳米结构都显示出依赖于光化学反应速率，增加的反应速率对应于更高的粘弹性模量、更低的分形维数和更高的分形簇尺寸。反应速率依赖性的变化与扩散和速率限制组装之间的转变一致，并且提出粘弹性响应的相应变化源自非分形耗尽区域的存在，这通过 SAXS 得到证实。这种可控的纳米结构和粘弹性为精确控制水凝胶性能提供了一种潜在途径，而无需进行分子修饰。
