Rate-based approach for controlling the mechanical properties of 'thiol-ene' hydrogels formed with visible light.
Rate-based approach for controlling the mechanical properties of 'thiol-ene' hydrogels formed with visible light.
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DOI：
10.1039/c9py00447e
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发表时间：
2019-08
影响因子：
4.6
通讯作者：
Katherine L. Wiley;Elisa M. Ovadia;C. J. Calo;Rebecca E. Huber;April M. Kloxin
中科院分区：
文献类型：
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作者：
Katherine L. Wiley;Elisa M. Ovadia;C. J. Calo;Rebecca E. Huber;April M. Kloxin
合成水凝胶的机械性质传统上已经通过用于水凝胶形成的大分子结构单元的浓度、分子量或化学计量来控制。最近，由于网络异质性的差异（例如，缺陷），这些缺陷是基于凝胶化速率而产生的。在此基础上，在这项工作中，我们研究了一种基于速率的方法，用于控制水凝胶的机械性能，无论是最初还是暂时与光。具体地，合成水凝胶用可见光引发的硫醇-烯“点击”化学（PEG-8-辛烯，二硫醇连接基，具有中心在455 nm处的LED灯的光引发剂）形成，使用照射条件来控制形成速率和所得水凝胶的机械性质。此外，随后利用这些水凝胶内的缺陷，通过使用低剂量的长波长UV光（365 nm）的二次固化来对机械性能进行时间调制。如用杨氏模量和剪切模量测量的，观察到水凝胶的弹性随着用于水凝胶形成的光引发剂的光强度和浓度的增加而增加。原位测量的端基转化与魔角旋转（MAS 1H NMR）与这些机械性能的测量水凝胶形成过程中，这表明悬空的端基和循环有助于观察到的机械性能。悬挂端基提供反应性柄，用于水凝胶的时间硬化，其中观察到杨氏模量增加约2.5倍。这些研究证明了光聚合的速率可以如何通过照射波长、强度和时间来调节，以控制合成水凝胶的性质，这可能在从涂层到用于受控细胞培养和再生医学的生物材料的各种应用中证明是有用的。
The mechanical properties of synthetic hydrogels traditionally have been controlled with the concentration, molecular weight, or stoichiometry of the macromolecular building blocks used for hydrogel formation. Recently, the rate of formation has been recognized as an important and effective handle for controlling the mechanical properties of these water-swollen polymer networks, owing to differences in network heterogeneity (e.g., defects) that arise based on the rate of gelation. Building upon this, in this work, we investigate a rate-based approach for controlling mechanical properties of hydrogels both initially and temporally with light. Specifically, synthetic hydrogels are formed with visible light-initiated thiol-ene 'click' chemistry (PEG-8-norbornene, dithiol linker, LAP photoinitiator with LED lamp centered at 455 nm), using irradiation conditions to control the rate of formation and the mechanical properties of the resulting hydrogels. Further, defects within these hydrogels were subsequently exploited for temporal modulation of mechanical properties with a secondary cure using low doses of long wavelength UV light (365 nm). The elasticity of the hydrogel, as measured with Young's and shear moduli, was observed to increase with increasing light intensity and concentration of photoinitiator used for hydrogel formation. In situ measurements of end group conversion during hydrogel formation with magic angle spinning (MAS 1H NMR) correlated with these mechanical properties measurements, suggesting that both dangling end groups and looping contribute to the observed mechanical properties. Dangling end groups provide reactive handles for temporal stiffening of hydrogels with a secondary UV-initiated thiol-ene polymerization, where an increase in Young's modulus by a factor of ~ 2.5x was observed. These studies demonstrate how the rate of photopolymerization can be tuned with irradiation wavelength, intensity, and time to control the properties of synthetic hydrogels, which may prove useful in a variety of applications from coatings to biomaterials for controlled cell culture and regenerative medicine.