多元介孔MOFs:通过调节表面亲水/疏水性实现酶固定化的多功能平台

Multivariate mesoporous MOFs with regulatable hydrophilic/hydrophobic surfaces as a versatile platform for enzyme immobilization

作为高效的生物催化剂,酶在食品加工、医药制造、化学工业和能源开发等众多领域发挥着重要作用.然而,游离状态的酶由于存在稳定性差、易失活、难以回收利用及不适用于连续化生产等问题,限制了其广泛应用.为了解决上述难题,人们探索发展了固定化酶技术.固定化酶不仅保留了原有的催化活性,而且在稳定性方面有了显著提升,从而极大地提高了酶的利用效率.随着固定化酶材料和酶工程领域的不断发展,固定化酶技术为酶的应用开辟了更广阔的前景.沸石-咪唑骨架材料-8(ZIF-8)作为一种金属-有机骨架(MOFs)材料,因其独特的结构特性而被广泛用作酶固定化载体.然而,ZIF-8的微孔结构和固有的疏水性,以及前体物2-甲基咪唑(2-MeIm)的质子化现象,常常影响固定化酶的活性.为克服这些限制,本文采用多元配体竞争和孔隙工程相结合的策略,设计并制备了一种具有可调节亲水/疏水表面的新型多元介孔MOFs(mMOFs),并用作酶固定化载体.在mMOFs的制备过程中,采用亲水性和配位能力更强的3-甲基-1H-1,2,4-三唑(3-MTZ)和5-甲基四唑(5-MTA)配体,以部分替代传统的2-MeIm配体.随后,这些多元配体(包括2-MeIm,3-MTZ和5-MTA)与七水硫酸锌结合,在甲醇溶液中通过自凝聚作用形成透明的胶体溶液,进而完全溶解在水中.在此过程中,七水硫酸锌发挥了软模板的作用,引导介孔的形成,从而成功制备出新型多元介孔mMOFs.接着,利用这些mMOFs作为酶固定化的载体,固定了辣根过氧化物酶(HRP)和葡萄糖氧化酶(GOx),并详细研究了其催化性能.结果表明,与传统的ZIF-8载体相比,以mMOFs为载体的固定化酶展现出了更高的酶活性和稳定性.催化性能提升主要归因于mMOFs的亲水性和介孔结构改善了酶和底物间的传质,同时2-MeIm的质子化效应减弱也为酶提供了优良的微环境,稳定了酶的构象.综上,本文采用多元配体竞争与孔隙工程相结合的策略,成功构建了一种具有可调节亲水/疏水表面的新型多元介孔mMOFs,并用于酶固定化,所得固定化酶表现出较好的催化性能.通过深入的研究,揭示了该固定化酶表现出良好催化性能的作用机制,为可控设计制备性能优越的、以MOFs为载体的固定化酶提供了新思路,并为进一步拓宽MOFs材料的应用范围提供了参考.

Zeolitic imidazole frameworks materials-8(ZIF-8),a member of the metal-organic framework(MOFs)series,have been extensively used as a host matrix for enzyme immobilization.However,the microporous structure and hydrophobicity,as well as the protonation of the precursor 2-methylimidazole(2-MeIm)of ZIF-8,remain considerable challenges in maintaining the activity of immobilized enzymes.Here,novel multivariate mesoporous MOFs(mMOFs)with regulatable hydrophilic/hydrophobic surfaces were designed by the multivariate competitive strategy and pore modification engineering.3-Methyl-1H-1,2,4-triazole(3-MTZ)and 5-methyltetrazole(5-MTA)were employed to partially replace 2-MeIm.These were then combined with zinc sulfate heptahydrate(soft templates)to yield mMOFs in a methanol solution.As a proof-of-concept application,we used mMOFs as carriers for enzyme immobilization and investigated the properties of the immobilized enzymes.Benefiting from their mesoporous structure,hydrophilic surface,and improved microenvironment,multivariate mMOFs exhibit a strong ability to stabilize enzyme conformation and increase enzyme activity compared with traditional ZIF-8.Our study offers an avenue for the controllable preparation of well-designed MOF structures,which will further broaden the application opportunities of MOF materials for enzyme immobilization.