Oxygen-Mediated Enzymatic Polymerization of Thiol-Ene Hydrogels.
Oxygen-Mediated Enzymatic Polymerization of Thiol-Ene Hydrogels.
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DOI：
10.1039/c3tb21794a
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发表时间：
2014-05-07
期刊：
影响因子：
--
通讯作者：
Scott TF
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文献类型：
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作者：
Zavada SR;McHardy NR;Scott TF
响应于引发刺激而固化的材料目前用于几种生物医学和外科应用;然而，它们的临床应用将随着物理性质和生物相容性的改善而更加广泛。一种特别有前途的化学反应是基于硫醇-烯加成反应，这是一种自由基介导的逐步增长聚合反应，它对氧抑制具有抗性，因此是暴露于需氧条件下时降解的材料的极好候选物。在此，通过将多官能硫醇和烯丙基醚PEG单体的水溶液与酶自由基引发体系组合暴露于空气来聚合硫醇-烯基水凝胶。基于葡萄糖氧化酶、葡萄糖和Fe 2+的引发体系最初被研究，其中，在葡萄糖的存在下，葡萄糖氧化酶将氧还原成过氧化氢，过氧化氢然后被Fe 2+进一步还原以产生能够引发硫醇-烯聚合的羟基自由基。虽然该系统显示出在暴露于氧气后有效地引发聚合，但聚合速率并不随着Fe 2+浓度的升高而单调增加，这是由于在较高Fe 2+浓度下阻碍聚合的抑制反应。相反，用辣根过氧化物酶代替Fe 2+提供了一种引发体系，该体系不受铁介导的抑制反应的影响，并且能够获得增加的聚合速率。
Materials that solidify in response to an initiation stimulus are currently utilized in several biomedical and surgical applications; however, their clinical adoption would be more widespread with improved physical properties and biocompatibility. One chemistry that is particularly promising is based on the thiol–ene addition reaction, a radical-mediated step-growth polymerization that is resistant to oxygen inhibition and thus is an excellent candidate for materials that polymerize upon exposure to aerobic conditions. Here, thiol–ene-based hydrogels are polymerized by exposing aqueous solutions of multi-functional thiol and allyl ether PEG monomers, in combination with enzymatic radical initiating systems, to air. An initiating system based on glucose oxidase, glucose, and Fe2+ is initially investigated where, in the presence of glucose, the glucose oxidase reduces oxygen to hydrogen peroxide which is then further reduced by Fe2+ to yield hydroxyl radicals capable of initiating thiol–ene polymerization. While this system is shown to effectively initiate polymerization after exposure to oxygen, the polymerization rate does not monotonically increase with raised Fe2+ concentration owing to inhibitory reactions that retard polymerization at higher Fe2+ concentrations. Conversely, replacing the Fe2+ with horseradish peroxidase affords an initiating system is that is not subject to the iron-mediated inhibitory reactions and enables increased polymerization rates to be attained.