For complex cascade biocatalysis, multienzyme compartmentalization helps to optimize substrate transport channels and promote the orderly and tunable progress of step reactions. Herein, a simple and general synthesis strategy is proposed for the construction of a multienzyme biocatalyst by compartmentalizing glucose oxidase and horseradish peroxidase (GOx and HRP) within core–shell zeolite imidazole frameworks (ZIF)‐8@ZIF‐8 nanostructures. Owing to the combined effects of biomimetic mineralization and the fine regulation of the ZIF‐8 growth process, the uniform shell encloses the seed (core) surface by epitaxial growth, and the bienzyme system is accurately localized in a controlled manner. The versatility of this strategy is also reflected in ZIF‐67. Meanwhile, with the ability to covalently bind divalent metal ions, lithocholic acid (LCA) is used as a competitive ligand to improve the pore structure of the ZIF from a single micropore to a hierarchical micro/mesopore network, which greatly increases mass transfer efficiency. Furthermore, the multienzyme cascade reaction is exemplified by the oxidation of o‐phenylenediamine (OPD). The findings show that the bienzyme assembly strategy significantly affects the biocatalytic efficiency mainly by influencing the utilization efficiency of the intermediate (Hydrogen peroxide, H2O2) between the step reactions. This study sheds new light on facile synthetic routes to constructing in vitro multienzyme biocatalysts.
Conductive nanofillers usually act as nucleating agents in the semicrystalline polymer matrix, and the crystals formed on the filler surface can impede electrical percolation development. In this work, flexible poly(ether-block-amide)/carbon nanotube (PEBA/CNT) nanocomposites were fabricated for electromagnetic interference (EMI) shielding applications. It was demonstrated that CNTs can nucleate the crystallization of the polyamide (PA) block of PEBA and induce the transformation of the crystals from the γ-form to the α-form. Reducing the content of the PA block in PEBA from 50 to 20 wt % decreased the crystallinity of the nanocomposite and thus resulted in a higher electrical conductivity and an increment in EMI shielding performances. However, when ionically conductive polyethylene oxide was used as the polyether block, the hindrance effect of PA crystallization on electrical percolation was effectively mitigated, allowing for both high conductivity and enhanced amide dipole moment with a high PA content (e.g., 50 wt %), which is favorable for electromagnetic wave absorption. As a result, a high EMI shielding effectiveness with increased absorption can be achieved in PEBA/CNT nanocomposites.
Hollow-structured nanomaterials, featuring a porous crystalline structure and hollow interior, are conducive to achieving a compartmentalized architecture comprising diverse functional entities. In this study, we have constructed a novel fluorescent enzyme nanocomposite derived from the nanosized hollow ZIF-8 (H-ZIF-8) colloidosomes via a diffusion strategy. Insights into the underlying mechanisms revealed that the diffusion process was driven by mesopore properties and electrostatic interactions. It has also been demonstrated that the molecular sieving property of the colloidosome shell induced an exceptional compartmentalized structure, where nitrogendoped graphene quantum dots (N-GQDs) were anchored onto the outer surface of the nanosized H-ZIF-8 colloidosomes, whereas glucose oxidase (GOx) was homogeneously encapsulated in the entire cavity. The resultant nanocomposite inherited the mesopore properties of the colloidosome exoskeleton, catalytic ability of GOx, and fluorescence properties of N-GQDs. In particular, the porous properties of the nanosized H-ZIF-8 colloidosomes favored enrichment to target analytes, whereas the compartmentalized GOx and N-GQDs served as a "promoter" (initiate the biochemical reaction) and "signal unit" (intuitive observation) in the glucose probing system, respectively. Furthermore, anchoring N-GQDs onto the outer surface of the nanosized H-ZIF-8 resulted in tailoring of the fluorescence property of the nanocomposite. In the part of glucose sensing, the proposed fluorescence nanosensor could well quantify glucose within a range of 10 to 100 μM with a lower limit of detection of 5.4 μM. This proposed strategy presents opportunities to engineer novel metal−organic framework-based multifunctional nanocomposites and create new applications by combining their unique functions.
In vitro digestion methods that can accurately predict the estimated GI (eGI) values of complex carbohydrate foods, including biscuits, are worth exploring. In the current study, standard commercial biscuits with varied clinical GI values between 9~30 were digested using both the INFOGEST and single-enzyme digestion protocols. The digestion kinetic parameters were acquired through mathematical fitting by mathematical kinetics models. The results showed that compared with the INFOGEST protocol, the AUR180 deduced from digesting using either porcine pancreatin or α-amylase showed the best potential in predicting the eGI values. Accordingly, mathematical equations were established based on the relations between the AUR180 and the GI values. When digesting using porcine pancreatin, GI= 1.834 + 0.009 ×AUCR180 (R2= 0.952), and when digesting using only α-amylase, GI= 6.101 + 0.009 ×AUCR180 (R2=0.902). The AUR180 represents the area under the curve of the reducing-sugar content normalized to the total carbohydrates versus the digestion time in 180 min. The in vitro method presented enabled the rapid and accurate prediction of the eGI values of biscuits, and the validity of the formula was verified by another batch of biscuits with a known GI, and the error rate of most samples was less than 30%.
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