Modulating the biofunctionality of enzyme-MOF nanobiocatalyst through structure-switching aptamer for continuous degradation of BPA.

Encapsulating enzyme within MOF (enzyme-MOF) gives rise to new opportunity to improve the fragility of enzyme, but practical application of enzyme-MOF composite is far from being realized. The development of a novel enzyme-MOF composite system should simultaneously guarantee the enhanced activity and controllably complete recycling, and only in this way can we efficiently and economically utilize the enzyme-MOF composite. Herein, we addressed all these fundamental limitations of current enzyme-MOF composite by establishing aptamer-functionalized enzyme-MOF composite (HRP-ZIF-8@P1). HRP-ZIF-8@P1 relied on automatic structure switch of aptamer-target binding and aptamer-cDNA (complementary DNA) hybridization, achieving effectiveness in self-enriching substrate around HRP-ZIF-8@P1 to boost enzymatic activity first, subsequently hybridizing spontaneously with magnetically controllable cDNA sequence (Fe3O4@P3) to completely recover the HRP-ZIF-8@P1, where preferentially capturing substrate could further induce the release of the hybridized HRP-ZIF-8@P1 for automatically starting the cyclic enzyme catalysis. A 5.6-fold enhancement in the catalytic efficiency for BPA degradation was endowed, and 94.7% catalytic activity was retained for 8 consecutive degradations of BPA, both of which were even more significant than HRP-ZIF-8. Additionally, remarkable stability of HRP-ZIF-8@P1 was afforded by dual-layer protection of ZIF-8 and P1 in denaturing conditions. Taking the possibility of discovering an aptamer for any target into account, the aptamer-functionalized enzyme-MOF composites provide a generic and simple guide for simultaneously boosting enzymatic activity and controllably full recycling the enzyme-MOF systems, accelerating their commercial utilizations.

Green separation of bromelain in food sample with high retention of enzyme activity using recyclable aqueous two-phase system containing a new synthesized thermo-responsive copolymer and salt.

High cost and enzyme deactivation in purification process are the two main obstacles for the use of enzyme as green catalyst. The objective of this work was to overcome these limitations by developing a cost-effective aqueous two-phase system (ATPS) for efficient purification of enzymes with remarkable separation efficiency and high retention of enzyme activity. The ATPS was formed by thermo-responsive block copolymer PEG113-b-PNIPAM149 and salt as phase-forming components combining economy, recovery and sustainability. This strategy fabricated block copolymer with specified molecular weight and low LCST, which not only achieved better phase splitting but also ensured easy recycling for block copolymer. The developed ATPS demonstrated excellent extraction and biocompatibility for bromelain in real sample with 94.87% separation efficiency and 77.06% activity, which were remarkably higher than those obtained in EOPOEO-based ATPS. The recycling of copolymer was introduced to minimize cost, with recovery efficiency of 90% in the five cycles.