Abstract：
Metal-organic frameworks (MOFs) are favorable hosting materials for fixing enzymes to construct enzyme@MOF composites and to expand the applications of biocatalysts. However, the rigid structure of MOFs without tunable hollow voids and a confinement effect often limits their catalytic activities. Taking advantage of the smart soft polymers to overcome the limitation, herein, a protection protocol to encapsulate the enzyme in zeolitic imidazolate framework-8 (ZIF-8) was developed using a glutathione-sensitive liposome (L) as a soft template. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were first anchored on a light- and thermoresponsive porous poly(styrene-maleic anhydride-N,N-dimethylaminoethyl methacrylate-spiropyran) membrane (PSMDSP) to produce PSMDSP@GOx-HRP, which could provide a confinement effect by switching the UV irradiation or varying the temperature. Afterward, embedding PSMDSP@GOx-HRP in L and encapsulating PSMDSP@GOx-HRP@L into hollow ZIF-8 (HZIF-8) to form PSMDSP@GOx-HRP@HZIF-8 composites were performed, which proceeded during the crystallization of the framework following the removal of L by adding glutathione. Impressively, the biocatalytic activity of the composites was 4.45-fold higher than that of the free enzyme under UV irradiation at 47 °C, which could benefit from the confinement effect of PSMDSP and the conformational freedom of the enzyme in HZIF-8. The proposed composites contributed to the protection of the enzyme against harsh conditions and exhibited superior stability. Furthermore, a colorimetric assay based on the composites for the detection of serum glucose was established with a linearity range of 0.05-5.0 mM, and the calculated LOD value was 0.001 mM in a cascade reaction system. This work provides a universal design idea and a versatile technique to immobilize enzymes on soft polymer membranes that can be encapsulated in porous rigid MOF-hosts. It also holds potential for the development of smart polymer@enzyme@HMOFs biocatalysts with a tunable confinement effect and high catalytic performance.
摘要：
金属有机骨架（MOFs）是固定酶以构建酶@MOF复合材料并扩展生物催化剂应用的有利宿主材料。然而,MOFs的刚性结构没有可调的中空空隙和限制效应通常限制了它们的催化活性。利用智能软聚合物来克服这一限制，在这里，使用谷胱甘肽敏感的脂质体(L)作为软模板,开发了将酶包封在沸石咪唑酯骨架-8(ZIF-8)中的保护方案。首先将葡萄糖氧化酶（GOx）和辣根过氧化物酶（HRP）锚定在光响应和热响应的多孔聚（苯乙烯-马来酸酐-N，甲基丙烯酸N-二甲基氨基乙酯-螺吡喃）膜（PSMDSP）生产PSMDSP@GOx-HRP，这可以通过切换UV照射或改变温度来提供限制效果。之后,将PSMDSP@GOx-HRP嵌入L,将PSMDSP@GOx-HRP@L封装到中空ZIF-8(HZIF-8)中,形成PSMDSP@GOx-HRP@HZIF-8复合材料,在通过添加谷胱甘肽除去L后的框架结晶过程中进行。令人印象深刻的是,在47°C的紫外线照射下，复合材料的生物催化活性比游离酶的生物催化活性高4.45倍，这可能得益于PSMDSP的限制效应和HZIF-8酶的构象自由度。所提出的复合材料有助于保护酶免受苛刻条件的影响，并表现出优异的稳定性。此外，建立了基于复合物的比色测定法，用于检测血清葡萄糖，线性范围为0.05-5.0mM，在级联反应系统中计算的LOD值为0.001mM。这项工作提供了一种通用的设计思想和通用技术，可以将酶固定在可以封装在多孔刚性MOF宿主中的软聚合物膜上。它还具有开发具有可调限制效应和高催化性能的智能聚合物@酶@HMOFs生物催化剂的潜力。
