Highly Selective Entrapment of His-Tagged Enzymes on Superparamagnetic Zirconium-Based MOFs with Robust Renewability to Enhance pH and Thermal Stability

Immobilization of aldo-keto reductase on dopamine/polyethyleneimine functionalized magnetic cellulose nanocrystals to enhance the detoxification of patulin in fresh pear juice

Patulin (PAT) is a highly toxic mycotoxin, which can contaminate fruits and their products and cause harm to human health. Cellulose nanocrystals (CNCs) were functionalized by magnetite nanoparticles, dopamine (DA) and polyethyleneimine (PEI) to form a multifunctional nanocarrier (DA/PEI@Fe3O4/CNCs) for immobilizing aldo-keto reductase (MgAKR) to degrade PAT. The MgAKR-DA/PEI@Fe3O4/CNCs were reusable and environmentally friendly due to its surface area, high magnetization value, and oxygen/amine function. The immobilization method significantly improved reusability, resistance to proteolysis, temperature stability and storage stability of MgAKR-DA/PEI@Fe3O4/CNCs. With NADPH as a coenzyme, the detoxification rate of MgAKR-DA/PEI@Fe3O4/CNCs on PAT reached 100 % in phosphate buffer and 98 % in fresh pear juice. The quality of fresh pear juice was unaffected by MgAKR-DA/PEI@Fe3O4/CNCs and could be quickly separated by magnet after detoxification, which was convenient for recycling. It has broad application prospects in the control of PAT contamination in beverage products containing fruit and vegetable ingredients.

Signal-On Detection of Caspase-3 with Methylene Blue-Loaded Metal-Organic Frameworks as Signal Reporters

In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal-organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as the nanocarriers to load electroactive MB molecules. Recombinant hexahistidine (His6)-tagged streptavidin (rSA) was attached to the MOFs through the coordination interaction between the His6 tag in rSA and the metal ions on the surface of the MOFs. The acetylated peptide substrate Ac-GDEVDGGGPPPPC was immobilized on the gold electrode. In the presence of caspase-3, the peptide was specifically cleaved, leading to the release of the Ac-GDEVD sequence. A N-terminal amine group was generated and then biotinylated in the presence of biotin-NHS. Based on the strong interaction between rSA and biotin, rSA@MOF@MB was captured by the biotinylated peptide-modified electrode, producing a significantly amplified electrochemical signal. Caspase-3 was sensitively determined with a linear range from 0.1 to 25 pg/mL and a limit of detection down to 0.04 pg/mL. Further, the active caspase-3 in apoptosis inducer-treated HeLa cells was further quantified by this method. The proposed signal-on biosensor is compatible with the complex biological samples and shows great potential for apoptosis-related diagnosis and the screening of caspase-targeting drugs.

Endogenous crude Scutellaria baicalensis polysaccharide robustly enhances one-pot extraction and deglycosylation of baicalin

With the extensive application of baicalein in the treatment of cardiovascular and cerebrovascular diseases, its clinical and market demand has gradually expanded. But the natural yield of baicalein is very low, and it is mainly prepared by the deglycosylation of baicalin. However, the insolubility of baicalin in water significantly limits the deglycosylation of it under biocatalysis. To make biocatalysis of baicalin more efficient and environmental, a strategy was designed to enhance its water solubility through the solubilization mechanism of endogenous biological macromolecules, and the effect on the activity of glucuronidase was further explored. The results showed that wrapping with Scutellaria baicalensis polysaccharide (SBP) significantly improved the solubility of baicalin in water (the water solubility of baicalin increased by 23 times, BI/SBP = 1/12, w/w). It was not only contributed to the efficient production of baicalein by one-pot method, but also effectively improved the deglycosylation rate of baicalin (increase by 47.04 % in aqueous solution). With the help of the solubilization of endogenous polysaccharide on baicalin in aqueous solution, a green, low-cost and efficient method (one-pot method) was designed to simultaneously extract and enzymatic hydrolyze baicalin to prepare baicalein. Under the same conditions, the yield of one-pot method is 87.17 %, which was much higher than that of the conventional method (29.38 %). In addition, one-pot method with the aid of endogenous polysaccharide could simply and conveniently prepare aglycone of other insoluble natural flavonoids, which has a wide range of industrial application value.

One-Step Purification and Immobilization of Glycosyltransferase with Zn-Ni MOF for the Synthesis of Rare Ginsenoside Rh2

Uridine diphosphate (UDP)-glucosyltransferases (UGTs) have received increasing attention in the field of ginsenoside Rh2 conversion. By harnessing the metal chelation between transition metal ions and imidazole groups present on His-tagged enzymes, a specific immobilization of the enzyme within metal-organic frameworks (MOFs) is achieved. This innovative approach not only enhances the stability and reusability of the enzyme but also enables one-step purification and immobilization. Consequently, the need for purifying crude enzyme solutions is effectively circumvented, resulting in significant cost savings during experimentation. The use of immobilized enzymes in catalytic reactions has shown great potential for achieving higher conversion rates of ginsenoside Rh2. In this study, highly stable mesoporous Zn-Ni MOF materials were synthesized at 150 °C by a solvothermal method. The UGT immobilized on the Zn-Ni MOF (referred to as UGT@Zn-Ni MOF) exhibited superior pH adaptability and thermal stability, retaining approximately 76% of its initial activity even after undergoing 7 cycles. Furthermore, the relative activity of the immobilized enzyme remained at an impressive 80.22% even after 45 days of storage. The strong specific adsorption property of Zn-Ni MOF on His-tagged UGT was confirmed through analysis using polyacrylamide gel electrophoresis. UGT@Zn-Ni MOF was used to catalyze the conversion reaction, and the concentration of rare ginsenoside Rh2 was generated at 3.15 μg/mL. The results showed that Zn-Ni MOF is a material that can efficiently purify and immobilize His-tagged enzyme in one step and has great potential for industrial applications in enzyme purification and ginsenoside synthesis.

Novel biocatalysts based on enzymes in complexes with nano- and micromaterials

In today's world, there is a wide array of materials engineered at the nano- and microscale, with numerous applications attributed to these innovations. This review aims to provide a concise overview of how nano- and micromaterials are utilized for enzyme immobilization. Enzymes act as eco-friendly biocatalysts extensively used in various industries and medicine. However, their widespread adoption faces challenges due to factors such as enzyme instability under different conditions, resulting in reduced effectiveness, high costs, and limited reusability. To address these issues, researchers have explored immobilization techniques using nano- and microscale materials as a potential solution. Such techniques offer the promise of enhancing enzyme stability against varying temperatures, solvents, pH levels, pollutants, and impurities. Consequently, enzyme immobilization remains a subject of great interest within both the scientific community and the industrial sector. As of now, the primary goal of enzyme immobilization is not solely limited to enabling reusability and stability. It has been demonstrated as a powerful tool to enhance various enzyme properties and improve biocatalyst performance and characteristics. The integration of nano- and microscale materials into biomedical devices is seamless, given the similarity in size to most biological systems. Common materials employed in developing these nanotechnology products include synthetic polymers, carbon-based nanomaterials, magnetic micro- and nanoparticles, metal and metal oxide nanoparticles, metal-organic frameworks, nano-sized mesoporous hydrogen-bonded organic frameworks, protein-based nano-delivery systems, lipid-based nano- and micromaterials, and polysaccharide-based nanoparticles.

Immobilization of fatty acid photodecarboxylase in magnetic nickel ferrite nanoparticle

Fatty acid photodecarboxylase in Chlorella variabilis NC64A (CvFAP) performed excellent ability to exclusively decarboxylate renewable fatty acids for C1-shortened hydrocarbons fuel production under visible light. However, the large-scale application by such an approach is limited by the free state of CvFAP catalyst, which is unstable for efficient biofuel production. In this study, CvFAP was immobilized in magnetic nickel ferrite (NiFe₂O₄) nanoparticles for facile recovery by a simple procedure. The shift of Ni 2p in electron binding energy was detected to clarify the interaction between Ni²⁺ and histidine of CvFAP. The coordination of NiFe₂O₄ and CvFAP contributed to an efficient affinity binding with an immobilization capacity of 98 mg/g carrier. Hydrocarbon fuel concentration of 3.7 mM was obtained by NiFe₂O₄@CvFAP-induced photoenzymatic decarboxylation. The high stability of CvFAP in terms of residual enzyme activity of 79.7% and 68% at pH 9 and organic solvent ratio of 60%, respectively, were observed.

Multipoint Immobilization at Inert Center of Papain on Homo-Functional Diazo-Activated Silica Support: A Way of Restoring "Above Room-Temperature" Bio-Catalytic Sustainability

Although enzymes play a significant role in industrial applications, their potential usage at high-level efficiency, particularly above room temperature, has not yet been fully harnessed. It brings above room-temperature catalytic sustainability of an immobilized (imm.) bio-catalyst as a long pending issue to improve enzyme stability, activity, specificity, or selectivity, particularly the enantio-selectivity over the native-enzymes. At this juncture, in a robust methodology, a heterogeneous solid phase bio-catalyst, {Si(OSi)₄(H₂O)_1.03}_n=328{OSi(CH₃)₂-NH-C₆H₄-N═N}₄{papain}(H₂O)₂₅₁, has efficiently been prepared by immobilizing papain on homo-functionalized SG (silica-gel) via multipoint covalent attachment. The bio-catalyst is easy to be recovered and reused multiple times. The homo-functional -N═N⁺, which appears on the SG-surface, makes the multipoint diazo-links with the inert center of the tyrosine-moiety to couple the enzyme where all the amino, thiol, phenol, and so forth, groups of the protein, including those that belong to the active-site, remain intact. The immobilized enzyme (13.9 μmol g^-1) swims in pore-water within the pore-channel, remains stable up to 70 ± 5 °C, and exhibits wider temperature adaptability in performing its hydrolyzing activities. The relative activity, 78 ± 2% at 27 °C, remains quantitative for 60 days and can be reused for 60 cycles with 53% activity at room-temperature. The thermal (relative activity: 87%; incubated at 70 ± 5 °C for 24 h) and mechanical (relative activity: 92%; incubated at 2500 rpm for 2 h at 27 °C) stability was outstanding.

Magnetic metal-organic frameworks immobilized enzyme-based nano-biocatalytic systems for sustainable biotechnology

Nanobiocatalysts, in which enzyme molecules are integrated into/onto multifunctional materials, such as metal-organic frameworks (MOFs), have been fascinating and appeared as a new interface of nanobiocatalysis with multi-oriented applications. Among various nano-support matrices, functionalized MOFs with magnetic attributes have gained supreme interest as versatile nano-biocatalytic systems for organic bio-transformations. From the design (fabrication) to deployment (application), magnetic MOFs have manifested notable efficacy in manipulating the enzyme microenvironment for robust biocatalysis and thus assure requisite applications in several areas of enzyme engineering at large and nano-biocatalytic transformations, in particular. Magnetic MOFs-linked enzyme-based nano-biocatalytic systems offer chemo-regio- and stereo-selectivities, specificities, and resistivities under fine-tuned enzyme microenvironments. Considering the current sustainable bioprocesses demands and green chemistry needs, we reviewed synthesis chemistry and application prospects of magnetic MOFs-immobilized enzyme-based nano-biocatalytic systems for exploitability in different industrial and biotechnological sectors. More specifically, following a thorough introductory background, the first half of the review discusses various approaches to effectively developed magnetic MOFs. The second half mainly focuses on MOFs-assisted biocatalytic transformation applications, including biodegradation of phenolic compounds, removal of endocrine disrupting compounds, dye decolorization, green biosynthesis of sweeteners, biodiesel production, detection of herbicides and screening of ligands and inhibitors.

Rhodium-Based MOF-on-MOF Difunctional Core-Shell Nanoreactor for NAD(P)H Regeneration and Enzyme Directed Immobilization

An organometallic complex-catalyzed artificial coenzyme regeneration system has attracted widespread attention. However, the combined use of organometallic complex catalysts and natural enzymes easily results in mutual inactivation. Herein, we establish a rhodium-based metal-organic framework (MOF)-on-MOF difunctional core-shell nanoreactor as an artificial enzymatic NAD(P)H regeneration system. UiO67 as the core is used to capture rhodium molecules for catalyzing NAD(P)H regeneration. UiO66 as the shell is used to specifically immobilize His-tagged lactate dehydrogenase (LDH) and serve as a protection shield for LDH and [Cp*Rh(bpy)Cl]⁺ to prevent mutual inactivation. A variety of results indicate that UiO67@Rh@UiO66 has good activity in realizing NAD(P)H regeneration. Noteworthily, UiO67@Rh@UiO66@LDH maintains a high activity level even after 10 cycles. This work reports a novel NAD(P)H regeneration platform to open up a new avenue for constructing chemoenzyme coupling systems.

One-pot encapsulation of lactate dehydrogenase and Fe3O4 nanoparticles into a metal-organic framework: A novel magnetic recyclable biocatalyst for the synthesis of D-phenyllactic acid

The main challenges in bio-catalysis of d-phenyllactic acid (D-PLA) are poor tolerance of lactate dehydrogenase (LDH) to harsh environmental conditions and inability to recycle the catalyst. A novel magnetic framework composite was prepared as solid support for the immobilization of enzymes via one-pot encapsulation in this study. LDH/MNPs@MAF-7 was synthesized by the one-pot encapsulation of both LDH and magnetic nanoparticles (MNPs) in MAF-7. The LDH/MNPs@MAF-7 showed stable biological activity for the efficient biosynthesis of D-PLA. The structure and morphology of LDH/MNPs@MAF-7 were systematically characterized by SEM, FT-IR, XRD, VSM, XPS, TGA and N₂ sorption. These indicated that LDH/MNPs@MAF-7 was successfully synthesized, exhibiting enhanced resistance to acid and alkali, temperature and organic solvents. Furthermore, the bio-catalyst could be separated easily using a magnet, and the reusability was once considerably expanded with 80% of enzyme activity last after eight rounds of recycling. Therefore, LDH/MNPs@MAF-7 could be used as a potential biocatalyst for the biosynthesis of D-PLA due to its good stability and recovery properties.

Chitosan-regulated biomimetic hybrid nanoflower for efficiently immobilizing enzymes to enhance stability and by-product tolerance

Organic-inorganic hybrid nano-materials have been considered to be promising immobilization matrixes for enzymes due to their significantly enhanced reusability and stability of enzymes. Herein, we constructed a novel organic-inorganic hybrid nanoflower via biomacromolecule-regulated biomimetic mineralization to immobilize sucrose phosphorylase (SPase). It was found that chitosan (CS) effectively regulated the biomimetic mineralization of calcium phosphate (CaP), leading to the formation of flower-like hybrid materials for the entrapment of SPase via self-assembly to establish a nano-biocatalyst (CS-CaP@SPase). Upon immobilization, the obtained CS-CaP@SPase exhibited excellent pH, by-product and organic solvents tolerance, and storage stability. Specifically, at acidic condition (pH 4), CS-CaP@SPase performed over 80 % of initial activity, which was 2.42-folds higher than that of free SPase. The catalytic activity of free SPase was severely inhibited about 30 % in the presence of fructose (1.2 M), but CS-CaP@SPase only lost 5 % relative activity. The CS-CaP@SPase retained over 80 % of its relative activity, while the free SPase maintained <20 % of its relative activity in acetonitrile. The relative activity of CS-CaP@SPase was still retained about 80 % after 10 cycles and maintained 75 % after 15 days. Based on Raman spectra analysis, it was also found that the increased β-folding component of SPase in the secondary structure after immobilization was the main factor for its enhanced stability. It is reasonable to believe that biomacromolecule-regulated biomimetic mineralization could be potentially used as a promising method to immobilize enzymes with excellent stability and recyclability, thereby facilitating the preparation of highly efficient catalysts for industrial biocatalysts, biosensing, and biomedicine.

Glucuronides: From biological waste to bio-nanomedical applications

Long considered as no more than biological waste meant to be eliminated in urine, glucuronides have recently contributed to tremendous developments in the biomedical field, particularly against cancer. While glucuronide prodrugs monotherapy and antibody-directed enzyme prodrug therapy have been around for some time, new facets have emerged that combine the unique properties of glucuronides notably in the fields of antibody-drug conjugates and nanomedicine. In both cases, glucuronides are utilized as a vector to improve pharmacokinetics and confer localized activation of potent drugs at tumor sites while also decreasing systemic toxicity. Here we will discuss some of the most promising strategies using glucuronides to promote successful anti-tumor therapeutic treatments.

Lactate dehydrogenase encapsulated in a metal-organic framework: A novel stable and reusable biocatalyst for the synthesis of D-phenyllactic acid

In this study, we synthesized a novel biocatalyst by encapsulating lactate dehydrogenase (LDH) in the metal-organic framework ZIF-90 by one-pot embedding. It showed strong biological activity for efficient synthesis of D-phenyllactic acid (D-PLA). The morphology and structure of LDH@ZIF-90 was systematically characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, confocal laser scanning microscopy (CLSM) and gas sorption. According to thermogravimetric analysis (TGA), the enzyme loading of the biocatalyst was 3 %. The Michaelis-Menten constant (K_m) and maximal reaction rate (V_max) of LDH@ZIF-90 were similar to those of free LDH, which proved that ZIF-90 had good biocompatibility to encapsulate LDH. At the same time, LDH@ZIF-90 exhibited enhanced tolerance to temperature, pH and organic solvents, and its reusability was greatly improved with 68 % of initial enzyme activity remaining after 7 rounds of recylcing. Overall, LDH encapsulated in ZIF-90 may be an economically competitive and environmentally friendly novel biocatalyst for the synthesis of D-PLA.

Enhancing stability and by-product tolerance of β-glucuronidase based on magnetic cross-linked enzyme aggregates

β-glucuronidase is an important catalyst which is highly specific for β-glucuronides. Here, we constructed magnetic cross-linking β-glucuronidase aggregates (MCLEAs) to for the production of glycyrrhetinic acid (GA). Before crosslinking via glutaraldehyde, we used carbodiimide to enhance the interaction between enzymes and carboxyl-functionalized Fe₃O₄, efficiently improving the activity recovery. Compared to free enzymes, both k_cat and k_cat/K_m enhanced, indicating that crosslinking and aggregation brought higher catalytic efficiency to enzymes. MCLEAs enhanced pH and thermal stabilities and retained 63.3% of catalytic activity after 6 cycles. More importantly, it was first found that the glucuronic acid tolerance of β-glucuronidase after the formation of MCLEAs enhanced 221.5% in 10 mM of glucuronic acid. According to the Raman spectroscopy, the ordered structure of β-glucuronidase increased from 43.9% to 50.6% after immobilization, which explained the increased stability and tolerance. To sum up, MCLEAs provided an efficient strategy for immobilization of enzymes, which enhanced stability and glucuronic acid tolerance of enzymes. It might be an effective solution to the serious inhibition caused by by-products during the preparation of aglycone from natural glycosides, having a significant applied prospect in industry.