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Enzyme-polymer hybrids for highly stable functional materials and self-cleaning coatings.

机译：酶-聚合物杂化物，用于高度稳定的功能材料和自清洁涂料。

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摘要

Being deployed originally for biosynthesis or biodegradation, enzymes have also shown great potentials for development of functional materials. One particular challenge in deriving enzyme-based functional materials is the control of protein-material interactions for best compatibility, activity and stability.;One major effort was dedicated to the development of enzyme-functionalized polyurethane coatings to afford a self-cleaning functionality with a reasonable lifetime. To act effectively against surface gluing organic stains, the applicability and suitability of hydrolytic enzymes like amylase, protease and lipase have been evaluated. Enzymes were incorporated into polymeric coatings in a manner to ensure high activity and stability. In the final cured coatings, a small portion of enzyme molecules is partially exposed to the outer surface, enabling the desired self-cleaning functionality; whereas the majority of the enzyme is entrapped in the interior, forming a reservoir for the gradual replenishment. This special way of enzyme immobilization enabled a high surface activity that is concomitantly accompanied by longevity as needed in practical applications.;The enzyme was entrapped into coatings through direct dispersion of an aqueous enzyme solution into a hydrophobic prepolymer mixture. Enzyme loadings of up to 5% wt (dry mass) have been tested. The polymer-enzyme mixture was applied as a coating solution and subsequently cured for 30 min at 83°C, resulting in bioactive coatings with high surface enzyme activity (∼2.0 unit/cm2 for alpha-amylase and ∼0.18 unit/cm2 for protease). In the fully cured coatings the enzymes were entrapped uniformly in form of microspherical particles. Such coatings also demonstrated very good activities against real-life stains in absence of bulk water, including food stains, smashed insects and fingerprints. In comparison to enzyme-free coatings, the rate of stain removal of was accelerated by a factor up to five orders of magnitude. It was further demonstrated that self-cleaning coatings can be reused for more than 50 times.;Practical applications of such bioactive coatings also require outstanding durability against weathering and other detrimental effects. Strategies for improved enzyme retention were developed by alternating the enzyme distribution and improving crosslinking between enzyme and polymer. Several preparation parameters including pH of the enzyme solution, the post-addition of surfactant and NCO/OH ratio were found effective in manipulating the degree of enzyme-polymer crosslinking, enzyme activity, enzyme particle size and distribution.;A parallel study was performed to explore the advantages and limitations of enzyme entrapment into hydrophilic films. A hydrophilic matrix allows monophasic enzyme entrapment as in contrast to the two-phase PU coating system. Hydrogels made of polyacrylamide are known for being fully compatible with enzymes. The polymeric network is swollen in the water and becomes a rigid glass upon drying. It was assumed that final dry glassy PAG matrix had been in geometrical congruence with the structure of enzyme molecules entrapped inside, providing effective spatial confinement for the enzyme molecules. PAG with enzyme loadings of up to 2%, were prepared and examined in this study. Scanning electron microscope (SEM) characterization confirmed the dimensions of the pores of the annealed gels in the range tens of nanometers, comparable to the dimension of single protein molecules. PAG-enzyme composite showed tremendously improved enzyme stabilities, against thermal or solvent inactivation. The most dramatic stabilization was observed for PAG-glucose oxidase (GOx) composite. The half-life time for PAG-entrapped GOx at 75°C in pure ethanol was about half year, more than 6 orders of magnitude higher than that of it native counterpart, a result not achieved by another types of enzyme stabilization measures. Marked stability was further observed on the PAG-entrapped alpha-chymotrypsin implying such a spatial confinement method could be general to all the proteins. (Abstract shortened by UMI.).
机译：酶最初用于生物合成或生物降解，也显示出开发功能材料的巨大潜力。为了获得最佳的相容性，活性和稳定性，控制基于酶的功能性材料的一个特殊挑战是控制蛋白质与材料之间的相互作用。合理的寿命。为了有效地对抗表面胶粘的有机污渍，已经评估了水解酶如淀粉酶，蛋白酶和脂肪酶的适用性和适用性。将酶以确保高活性和稳定性的方式掺入聚合物涂层中。在最终的固化涂层中，一小部分酶分子部分暴露于外表面，从而实现了所需的自清洁功能；而大部分酶则被困在内部，形成了逐渐补充的储存空间。这种特殊的酶固定方法实现了高表面活性，并伴随着实际应用中的长寿命。通过将酶水溶液直接分散到疏水性预聚物混合物中，酶被包埋在涂层中。已测试了高达5％wt（干重）的酶负载量。聚合物酶混合物作为包衣溶液施用，随后在83°C下固化30分钟，形成具有高表面酶活性的生物活性涂层（α-淀粉酶约2.0单位/ cm2，蛋白酶约0.18单位/ cm2） 。在完全固化的涂层中，酶以微球形颗粒的形式均匀地包埋。在没有大量水（包括食物污渍，昆虫捣烂和指纹）的情况下，此类涂料还表现出了很好的抗现实污渍的活性。与不含酶的涂料相比，污渍的去除速率提高了五个数量级。进一步证明，自清洁涂料可以重复使用50次以上；此类生物活性涂料的实际应用还需要出色的耐候性和其他不利影响。通过改变酶的分布并改善酶与聚合物之间的交联，开发了改善酶保留的策略。发现了一些制备参数，包括酶溶液的pH，表面活性剂的后添加和NCO / OH的比例，可有效地控制酶与聚合物的交联度，酶活性，酶的粒径和分布。探索酶截留在亲水膜中的优点和局限性。与两相PU涂层系统相比，亲水性基质允许单相酶截留。由聚丙烯酰胺制成的水凝胶与酶完全相容。聚合物网络在水中溶胀，干燥后变成刚性玻璃。假定最终的干燥玻璃状PAG基质在几何结构上与内部截留的酶分子结构一致，从而为酶分子提供了有效的空间限制。制备并检验了酶含量高达2％的PAG。扫描电子显微镜（SEM）表征证实了退火凝胶的孔尺寸在数十纳米范围内，与单个蛋白质分子的尺寸相当。 PAG-酶复合物在抵抗热或溶剂失活方面显示出极大的酶稳定性。对于PAG-葡萄糖氧化酶（GOx）复合材料，观察到最显着的稳定性。含PAG的GOx在75°C的纯乙醇中的半衰期约为半年，比其天然对应物高出6个数量级，这是另一种酶稳定措施无法实现的结果。在包埋有PAG的α-胰凝乳蛋白酶上进一步观察到明显的稳定性，这表明这种空间限制方法可能对所有蛋白质都是通用的。 （摘要由UMI缩短。）。

著录项

  • 作者

    Wu, Songtao.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Engineering Chemical.;Engineering General.;Chemistry Biochemistry.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 225 p.
  • 总页数 225
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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