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Entrapment of enzymes in silica aerogels
Materials Today ( IF 24.2 ) Pub Date : 2020-03-01 , DOI: 10.1016/j.mattod.2019.09.021
Nir Ganonyan , Noam Benmelech , Galit Bar , Raz Gvishi , David Avnir

Abstract Aerogels, the world's lightest solids, possess extraordinary traits such as very low density, very high surface area, very high porosity and ultra-low heat conductivity. These traits made aerogels favorable in various applications, including high-performance thermal insulators, catalyst supports, electrode materials, random laser matrices, cosmic dust collectors and more. Of the many potential applications of aerogels, one of the most challenging has been the development of a general procedure for bioactive aerogels by the entrapment of enzymes within these air-light materials. The difficulty in reaching this “holy-grail” was dual: The special procedures for obtaining the unique structure of aerogel are destructive to enzymes; and the aerogels are extremely sensitive to any procedural modification. Thus, the use of pure silica aerogel for the entrapment of enzymes was not known. Here we present a generalized, bio-friendly procedure for the entrapment of enzymes in silica aerogel, retaining both the enzymatic activity and the air-light structure of the aerogel. All of the aerogel synthesis steps were modified and optimized for reducing the risk of enzyme denaturation, while preserving the aerogel characteristic structure of the composite. The entrapment of three enzymes of different types was demonstrated: glucose oxidase, acid phosphatase and xylanase. All aerogel-entrapped enzymes showed superior activity over the common method of sol–gel entrapment in xerogels, due to the much wider and open pore network of the former. Michaelis-Menten kinetics was observed for the entrapped enzymes, indicating that the enzymes are highly accessible and diffusional limitations are negligible. The Michaelis-Menten constant, Km, has remained at the same level, indicating that enzyme-substrate affinity was not affected. Thermal stabilization was observed for entrapped acid phosphatase reaching peak activity at 70 °C. Large molecular weight substrates such as xylan for xylanase, are no obstacle for the aerogel matrix, while completely inapplicable for the xerogel. All of these properties are highly relevant for biotechnological applications.

中文翻译:

二氧化硅气凝胶中酶的截留

摘要 气凝胶是世界上最轻的固体,具有极低的密度、极高的表面积、极高的孔隙率和超低的热导率等非凡特性。这些特性使气凝胶在各种应用中受到青睐,包括高性能绝热体、催化剂载体、电极材料、随机激光矩阵、宇宙集尘器等。在气凝胶的许多潜在应用中,最具挑战性的一个是通过在这些空气轻材料中捕获酶来开发生物活性气凝胶的一般程序。达到这个“圣杯”的困难是双重的:获得气凝胶独特结构的特殊程序对酶具有破坏性;气凝胶对任何程序修改都非常敏感。因此,使用纯二氧化硅气凝胶包埋酶是未知的。在这里,我们提出了一种通用的、生物友好的方法,用于在二氧化硅气凝胶中捕获酶,同时保留了气凝胶的酶活性和空气光结构。所有气凝胶合成步骤都经过修改和优化,以降低酶变性的风险,同时保留复合材料的气凝胶特征结构。证明了三种不同类型酶的截留:葡萄糖氧化酶、酸性磷酸酶和木聚糖酶。所有气凝胶包埋的酶都显示出优于干凝胶中溶胶-凝胶包埋的常用方法的活性,因为前者具有更宽和开放的孔隙网络。观察到包埋酶的 Michaelis-Menten 动力学,表明酶是高度可及的,并且扩散限制可以忽略不计。Michaelis-Menten 常数 Km 保持在同一水平,表明酶-底物亲和力不受影响。观察到夹带的酸性磷酸酶在 70°C 时达到峰值活性的热稳定性。大分子量底物,如木聚糖酶的木聚糖,对气凝胶基质没有障碍,而完全不适用于干凝胶。所有这些特性都与生物技术应用高度相关。大分子量底物,如木聚糖酶的木聚糖,对气凝胶基质没有障碍,而完全不适用于干凝胶。所有这些特性都与生物技术应用高度相关。大分子量底物,如木聚糖酶的木聚糖,对气凝胶基质没有障碍,而完全不适用于干凝胶。所有这些特性都与生物技术应用高度相关。
更新日期:2020-03-01
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