Enzymes immobilized in mesoporous silica: a physical-chemical perspective

Engineering a Mesoporous Silicon Nanoparticle Cage to Enhance Performance of a Phosphotriesterase Enzyme for Degradation of VX Nerve Agent

The organophosphate (OP)-hydrolyzing enzyme phosphotriesterase (PTE, variant L7ep-3a) immobilized within a partially oxidized mesoporous silicon nanoparticle cage is synthesized and the catalytic performance of the enzyme@nanoparticle construct for hydrolysis of a simulant, dimethyl p-nitrophenyl phosphate (DMNP), and the live nerve agent VX is benchmarked against the free enzyme. In a neutral aqueous buffer, the optimized construct shows a ≈2-fold increase in the rate of DMNP turnover relative to the free enzyme. Enzyme@nanoparticles with more hydrophobic surface chemistry in the interior of the pores show lower catalytic activity, suggesting the importance of hydration of the pore interior on performance. The enzyme@nanoparticle construct is readily separated from the neutralized agent; the nanoparticle is found to retain DMNP hydrolysis activity through seven decontamination/recovery cycles. The nanoparticle cage stabilizes the enzyme against thermal denaturing and enzymatic (trypsin) degradation conditions relative to free enzyme. When incorporated into a topical gel formulation, the PTE-loaded nanoparticles show high activity toward the nerve agent VX in an ex vivo rabbit skin model. In vitro acetylcholinesterase (AChE) assays in human blood show that the enzyme@nanoparticle construct decontaminates VX, preserving the biological function of AChE when exposed to an otherwise incapacitating dose.

In-situ stabilized lipase in calcium carbonate microparticles for activation in solvent-free transesterification for biodiesel production

Biodiesel serves as a crucial biofuel alternative to petroleum-based diesel fuels, achieved through enzymatic transesterification of oil substrates. This study aims to investigate stabilized lipase (LP) within calcium carbonate (CaCO3) microparticles as a catalyst for solvent-free transesterification in biodiesel synthesis. The specific hydrolysis activity of the in-situ immobilized LP was 66% of that of free LP. However, the specific transesterification activity of immobilized LP in the solvent-free phase for biodiesel production was 2.29 times higher than that of free LP. These results suggest that the interfacial activation of LP molecules is facilitated by the inorganic CaCO3 environment. The immobilized LP demonstrated higher biodiesel production levels with superior stability compared to free LP, particularly regarding methanol molar ratio and temperature. To the best of our knowledge, there are no previous reports on the in-situ immobilization of LP in a CaCO3 carrier without any crosslinker as an interfacial-activated biocatalyst for biodiesel production.

Revolutionizing protein hydrolysis in wastewater: Innovative immobilization of metagenome-derived protease in periodic mesoporous organosilica with imidazolium framework

This research focused on utilizing periodic mesoporous organosilica with imidazolium framework (PMO-IL), to immobilize a metagenome-sourced protease (PersiProtease1), thereby enhancing its functional efficiency and catalytic effectiveness in processing primary proteins found in tannery wastewater. The successful immobilization of enzyme was confirmed through the use of N2 adsorption-desorption experiment, XRD, FTIR, TEM, FESEM, EDS and elemental analytical techniques. The immobilized enzyme exhibited greater stability in the presence of various metal ions and inhibitors compared to its free form. Furthermore, enzyme binding to PMO-IL nanoparticles (NPs) reduced leaching, evidenced by only 11.41 % of enzyme leakage following a 120-min incubation at 80 °C and 6.99 % after 240 min at 25 °C. Additionally, PersiPro@PMO-IL maintained impressive operational consistency, preserving 62.24 % of its activity over 20 cycles. It also demonstrated notable stability under saline conditions, with an increase of 1.5 times compared to the free enzyme in the presence of 5 M NaCl. The rate of collagen hydrolysis by the immobilized protease was 46.82 % after a 15-minute incubation at 60 °C and marginally decreased to 39.02 % after 20 cycles indicative of sustained efficacy without significant leaching throughout the cycles. These findings underscore the effectiveness of PMO-IL NPs as a viable candidate for treating wastewater containing protein.

Carbonic anhydrase encapsulation using bamboo cellulose scaffolds for efficient CO2 capture and conversion

Utilizing carbonic anhydrase (CA) to catalyze CO2 hydration offers a sustainable and potent approach for carbon capture and utilization. To enhance CA's reusability and stability for successful industrial applications, enzyme immobilization is essential. In this study, delignified bamboo cellulose served as a renewable porous scaffold for immobilizing CA through oxidation-induced cellulose aldehydation followed by Schiff base linkage. The catalytic performance of the resulting immobilized CA was evaluated using both p-NPA hydrolysis and CO2 hydration models. Compared to free CA, immobilization onto the bamboo scaffold increased CA's optimal temperature and pH to approximately 45 °C and 9.0, respectively. Post-immobilization, CA activity demonstrated effective retention (>60 %), with larger scaffold sizes (i.e., 8 mm diameter and 5 mm height) positively impacting this aspect, even surpassing the activity of free CA. Furthermore, immobilized CA exhibited sustained reusability and high stability under thermal treatment and pH fluctuation, retaining >80 % activity even after 5 catalytic cycles. When introduced to microalgae culture, the immobilized CA improved biomass production by ∼16 %, accompanied by enhanced synthesis of essential biomolecules in microalgae. Collectively, the facile and green construction of immobilized CA onto bamboo cellulose block demonstrates great potential for the development of various CA-catalyzed CO2 conversion and utilization technologies.

Adsorption of β-Lactoglobulin on Thiol-Functionalized Mesoporous Silica

SBA-15 mesoporous materials were synthesized with different pore sizes (5 and 10 nm) and thiol-functionalized groups and then characterized to describe their ability to differentially adsorb β-lactoglobulin (BLG), a globular protein with an ellipsoid shape measuring 6.9 nm in length and 3.6 nm in width. All adsorption experiments showed that the adsorption capacities of mesoporous materials for BLG were dependent on the duration of contact between the two materials (mesoporous material and BLG) and the initial BLG concentration. It was also shown that the pore sizes and thiol groups of SBA-15-based adsorbents are important factors for the BLG adsorption capacities. Among the tested adsorbents, thiol-functionalized SBA-15 with a 10 nm pore size (SBA-15-SH-10) showed the highest adsorption capacity (0.560 g·g-1) under optimal experimental conditions. Kinetics studies demonstrated that the adsorption occurs predominantly inside the pores, with interactions occurring on heterogeneous surfaces. In addition, the thermodynamic parameters indicate a spontaneous and exothermic behavior of the BLG adsorption process onto the thiol-functionalized SBA-15 mesoporous adsorbent. Finally, the characterization of the SBA-15-SH-10 adsorbent at 308 K showed the occurrence of an oxidation reaction of the thiol groups to sulfonate groups during the adsorption process as confirmed by Raman spectroscopy. The spectra recorded after adsorption of the protein showed that this adsorption did not affect the secondary structure of the protein.

Preparation of a heterogeneous biocatalyst through Thermomyces lanuginosus lipase immobilization on pore-expanded SBA-15

Heterogeneous biocatalysts were prepared by adsorbing T. lanuginosus lipase (TLL) onto uncalcined (SBAUC-TLL) and calcined (SBAC-TLL) SBA-15, using ammonium fluoride as a pore expander to facilitate TLL immobilization. At an enzyme load of 1 mg/g, high immobilization yields (>90 %) and recovered activities (>80 % for SBAUC-TLL and 70 % for SBAC-TLL) were achieved. When increasing the enzyme load to 5 mg/g, the immobilization yield of SBAUC-TLL was 80 %, and the recovered activity was 50 %, while SBAC-TLL had a yield of 100 % and a recovered activity of 36 %. Crosslinking with glutaraldehyde (GA) was conducted to improve stability (SBAUC-TLL-GA and SBAC-TLL-GA). Although SBAC-TLL-GA lost 25 % of initial activity after GA modifications, it exhibited the highest thermal (t1/2 = 5.7 h at 65 °C), when compared to SBAC-TLL (t1/2 = 12 min) and the soluble enzyme (t1/2 = 36 min), and operational stability (retained 100 % activity after 5 cycles). Both biocatalysts presented high storage stability since they retained 100 % of initial activity for 30 days. These results highlight SBA-15's potential as an enzyme support and the protocol's efficacy in enhancing stability, with implications for industrial applications in the food, chemical, and pharmaceutical sectors.

Magnetic Multienzyme@Metal-Organic Material for Sustainable Biodegradation of Insoluble Biomass

Biodegradation of insoluble biomass such as cellulose via carbohydrase enzymes is an effective approach to break down plant cell walls and extract valuable materials therein. Yet, the high cost and poor reusability of enzymes are practical concerns. We recently proved that immobilizing multiple digestive enzymes on metal-organic materials (MOMs) allows enzymes to be reused via gravimetric separation, improving the cost efficiency of cereal biomass degradation [ACS Appl. Mater. Interfaces 2021, 13, 36, 43085-43093]. However, this strategy cannot be adapted for enzymes whose substrates or products are insoluble (e.g., cellulose crystals). Recently, we described an alternative approach based on magnetic metal-organic frameworks (MOFs) using model enzymes/substrates [ACS Appl. Mater. Interfaces 2020, 12, 37, 41794-41801]. Here, we aim to prove the effectiveness of combining these two strategies in cellulose degradation. We immobilized multiple carbohydrase enzymes that cooperate in cellulose degradation via cocrystallization with Ca2+, a carboxylate ligand (BDC) in the absence and presence of magnetic nanoparticles (MNPs). We then compared the separation efficiency and enzyme reusability of the resultant multienzyme@Ca-BDC and multienzyme@MNP-Ca-BDC composites via gravimetric and magnetic separation, respectively, and found that, although both composites were effective in cellulose degradation in the first round, the multienzyme@MNP-Ca-BDC composites displayed significantly enhanced reusability. This work provides the first experimental demonstration of using magnetic solid supports to immobilize multiple carbohydrase enzymes simultaneously and degrade cellulose and promotes green/sustainable chemistry in three ways: (1) reusing the enzymes saves energy/sources to prepare them, (2) the synthetic conditions are "green" without generating unwanted wastes, and (3) using our composites to degrade cellulose is the first step of extracting valuable materials from sustainable biomasses such as plants whose growth does not rely on nonregeneratable resources.

Tuning Electrostatic Interactions To Control Orientation of GFP Protein Adsorption on Silica Surface

The adsorption of green fluorescent protein (GFP) on silica surfaces has been the subject of growing interest due to its potential applications in various fields, including biotechnology and biomedicine. In this study, we used all-atom molecular dynamics simulations to investigate the charge-driven adsorption of wild type GFP and its supercharged variants on silica surfaces. The results showed that the positively charged variant of GFP adsorbed on the negatively charged silica surface with minimal loss in its secondary structure. Further studies were conducted to understand the role of surface charge distribution on two other positively charged variants of GFP, and the results showed that the orientation of GFP on silica can be easily tuned by careful mutations of the charged amino acid residues on the GFP. This study provides valuable molecular insights into the role of electrostatic-driven adsorption of GFP and highlights the importance of charge interactions in the adsorption process.

Organismal Function Enhancement through Biomaterial Intervention

Living organisms in nature, such as magnetotactic bacteria and eggs, generate various organic-inorganic hybrid materials, providing unique functionalities. Inspired by such natural hybrid materials, researchers can reasonably integrate biomaterials with living organisms either internally or externally to enhance their inherent capabilities and generate new functionalities. Currently, the approaches to enhancing organismal function through biomaterial intervention have undergone rapid development, progressing from the cellular level to the subcellular or multicellular level. In this review, we will concentrate on three key strategies related to biomaterial-guided bioenhancement, including biointerface engineering, artificial organelles, and 3D multicellular immune niches. For biointerface engineering, excess of amino acid residues on the surfaces of cells or viruses enables the assembly of materials to form versatile artificial shells, facilitating vaccine engineering and biological camouflage. Artificial organelles refer to artificial subcellular reactors made of biomaterials that persist in the cytoplasm, which imparts cells with on-demand regulatory ability. Moreover, macroscale biomaterials with spatiotemporal regulation characters enable the local recruitment and aggregation of cells, denoting multicellular niche to enhance crosstalk between cells and antigens. Collectively, harnessing the programmable chemical and biological attributes of biomaterials for organismal function enhancement shows significant potential in forthcoming biomedical applications.

Natural Silicates Encapsulated Enzymes as Green Biocatalysts for Degradation of Pharmaceuticals

Biocatalytic degradation with the use of enzymes has gained great attention in the past few years due to its advantages of high efficiency and environmental friendliness. Novel, cost-effective, and green nanoadsorbents were produced in this study, using natural silicates as an enzyme host matrix for core-shell immobilization technique. With the natural silicate as a core and silica layer as a shell, it was possible to encapsulate two different enzymes: horseradish peroxidase (HRP) and laccase, for removal and degradation of three pharmaceuticals: diclofenac (DFC), carbamazepine (CBZ), and paracetamol (PC). The biocatalysts demonstrated high oxidation rates for the selected pollutants. In particular HRP immobilized fly ash and perlite degraded DFC and PC completely during 3 days of interaction and also showed high degradation rates for CBZ. Immobilized laccase was successful in PC degradation, where up to 70-80% degradation of the compounds with aromatic rings was reported by NMR measurements for a high drug concentration of 10 μg/mL. The immobilization method played a significant role in this process by providing stability and protection for the enzymes over 3 weeks. Furthermore, the enzymes acted differently in the three chosen supports due to their complex chemical composition, which could have an effect on the overall enzyme activity.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Preparation of a Mesoporous Biosensor for Human Lactate Dehydrogenase for Potential Anticancer Inhibitor Screening

Cancer is the second leading cause of death worldwide, with a dramatic impact due to the acquired resistance of cancers to used chemotherapeutic drugs and treatments. The enzyme lactate dehydrogenase (LDH-A) is responsible for cancer cell proliferation. Recently the development of selective LDH-A inhibitors as drugs for cancer treatment has been reported to be an efficient strategy aiming to decrease cancer cell proliferation and increase the sensitivity to traditional chemotherapeutics. This study aims to obtain a stable and active biocatalyst that can be utilized for such drug screening purposes. It is conceived by adopting human LDH-A enzyme (hLDH-A) and investigating different immobilization techniques on porous supports to achieve a stable and reproducible biosensor for anticancer drugs. The hLDH-A enzyme is covalently immobilized on mesoporous silica (MCM-41) functionalized with amino and aldehyde groups following two different methods. The mesoporous support is characterized by complementary techniques to evaluate the surface chemistry and the porous structure. Fluorescence microscopy analysis confirms the presence of the enzyme on the support surface. The tested immobilizations achieve yields of ≥80%, and the best retained activity of the enzyme is as high as 24.2%. The optimal pH and temperature of the best immobilized hLDH-A are pH 5 and 45 °C for the reduction of pyruvate into lactate, while those for the free enzyme are pH 8 and 45 °C. The stability test carried out at 45 °C on the immobilized enzyme shows a residual activity close to 40% for an extended time. The inhibition caused by NHI-2 is similar for free and immobilized hLDH-A, 48% and 47%, respectively. These findings are significant for those interested in immobilizing enzymes through covalent attachment on inorganic porous supports and pave the way to develop stable and active biocatalyst-based sensors for drug screenings that are useful to propose drug-based cancer treatments.

Biodegradation of Aflatoxin B1 in Peanut Oil by an Amphipathic Laccase-Inorganic Hybrid Nanoflower

Aflatoxin B₁ (AFB₁) contamination is an important issue for the safety of edible oils. Enzymatic degradation is a promising approach for removing mycotoxins in a specific, efficient, and green manner. However, enzymatic degradation of mycotoxins in edible oil is challenging as a result of the low activity and stability of the enzyme. Herein, a novel strategy was proposed to degrade AFB₁ in peanut oil using an amphipathic laccase-inorganic hybrid nanoflower (Lac NF-P) as a biocatalyst. Owing to the improved microenvironment of the enzymatic reaction and the enhanced stability of the enzyme structure, the proposed amphipathic Lac NF-P showed 134- and 3.2-fold increases in the degradation efficiency of AFB₁ in comparison to laccase and Lac NF, respectively. AFB₁ was removed to less than 0.96 μg/kg within 3 h when using Lac NF-P as a catalyst in the peanut oil, with the AFB₁ concentration ranging from 50 to 150 μg/kg. Moreover, the quality of the peanut oil had no obvious change, and no leakage of catalyst was observed after the treatment of Lac NF-P. In other words, our study may open an avenue for the development of a novel biocatalyst for the detoxification of mycotoxins in edible oils.

Unveiling the orientation and dynamics of enzymes in unstructured artificial compartments of metal-organic frameworks (MOFs)

Confining enzymes in well-shaped MOF compartments is a promising approach to mimic the cellular environment of enzymes and determine enzyme structure-function relationship therein. Under the cellular crowding, however, enzymes can also be confined in unstructured spaces that are close to the shapes/outlines of the enzyme. Therefore, for a better understanding of enzymes in their physiological environments, it is necessary to study enzymes in these unstructured spaces. However, practically it is challenging to create compartments that are close to the outline of an enzyme and probe enzyme structural information therein. Here, for proof-of-principle, we confined a model enzyme, lysozyme, in the crystal defects of a MOF via co-crystallization, where lysozyme served as the nuclei for MOF crystal scaffolds to grow on so that unstructured spaces close to the outline of lysozyme are created, and determined enzyme relative orientation and dynamics. This effort is important for understanding enzymes in near-native environments and guiding the rational design of biocatalysts that mimic how nature confines enzymes.

Silica-Based Nanomaterials for Diabetes Mellitus Treatment

Diabetes mellitus, a chronic metabolic disease with an alarming global prevalence, is associated with several serious health threats, including cardiovascular diseases. Current diabetes treatments have several limitations and disadvantages, creating the need for new effective formulations to combat this disease and its associated complications. This motivated the development of therapeutic strategies to overcome some of these limitations, such as low therapeutic drug bioavailability or poor compliance of patients with current therapeutic methodologies. Taking advantage of silica nanoparticle characteristics such as tuneable particle and pore size, surface chemistry and biocompatibility, silica-based nanocarriers have been developed with the potential to treat diabetes and regulate blood glucose concentration. This review discusses the main topics in the field, such as oral administration of insulin, glucose-responsive devices and innovative administration routes.

Immobilization of Kluyveromyces lactis β-Galactosidase on Meso-macroporous Silica: Use of Infrared Spectroscopy to Rationalize the Catalytic Efficiency

Enzyme immobilization on adequate carriers is a challenging strategy. Understanding the enzyme-carrier interactions and their effects on enzyme conformation and bioactivity is critical. In this study, a meso-macropores silica (MMS) was used to immobilize β-galactosidase from the yeast Kluyveromyces lactis (β-gal-KL) by physical adsorption. The bioactivity of the immobilized β-gal-KL was altered, evidenced by the increased K_m , decreased V_max and k_cat , and increased activity at alkaline values. By performing infrared spectroscopy analysis and subsequent secondary structure assessment from the amide I band, the immobilized β-gal-KL suffered a β-sheet (∼31-35 %) to α-helix (∼15-19 %) transition with increased turns (∼21-22 %) with respect to the free β-gal-KL having ∼12 % α-helix, ∼42 % β-sheet, and ∼17 % turns. These findings led us to correlate the observed bioactivity performance to structural alterations to a non-native conformation. The presented line of thought can lead to a better understanding of the reasons causing bioactivity alterations upon enzyme immobilization.

Effective immobilization of lactate dehydrogenase onto mesoporous silica

This study presents that covalent immobilization technique has been utilized for the immobilization of l-lactate dehydrogenase (l-LDH) from porcine on mesoporous silica. To develop mesoporous silica as support material for use in l-LDH immobilization, the particle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. The effect of some parameters such as glutaraldehyde concentration, immobilization pH, initial enzyme concentration, and immobilization time was investigated and the optimum conditions for these parameters were determined as 1% (w/v), pH 8.0, 1 mg/ml, and 120 min, respectively. The maximum working pH and temperature for the oxidation of lactate to pyruvate reaction were determined as 10.0 and 35°C for free and 9.0 and 40°C for immobilized l-LDH, respectively. The kinetic parameters (K_m and V_max ) of l-LDH for the oxidation of lactate to pyruvate reaction were examined as 1.02 mM and 7.58 U/mg protein for free and 0.635 mM and 1.7 U/mg protein for immobilized l-LDH, respectively. Moreover, the immobilized l-LDH was 1.3-fold more stable than free l-LDH at 25°C according to calculated t_1/2 values. The immobilized l-LDH retained 80% of its initial activity in a batch reactor after 14 reuses.

Switch off/switch on of a cysteinyl protease as a way to preserve the active catalytic group by modification with a reversible covalent thiol modifier: Immobilization of ficin on vinyl-sulfone activated supports

The immobilization of ficin (a cysteinyl proteases) on vinyl sulfone agarose produced its almost full inactivation. It was observed that the incubation of the free and immobilized enzyme in β-mercaptoethanol produced a 20 % of enzyme activity recovery, suggesting that the inactivation due to the immobilization could be a consequence of the modification of the catalytic Cys. To prevent the enzyme inactivation during the immobilization, switching off of ficin via Cys reaction with dipyridyl-disulfide was implemented, giving a reversible disulfide bond that produced a fully inactive enzyme. The switch on of ficin activity was implemented by incubation in 1 M β-mercaptoethanol. Using this strategy to immobilize the enzyme on vinyl sulfone agarose beads, the expressed activity of the immobilized ficin could be boosted up to 80 %. The immobilized enzyme presented a thermal stabilization similar to that obtained using ficin-glyoxyl-agarose beads. This procedure may be extended to many enzymes containing critical Cys, to permit their immobilization or chemical modification.

Controllable Enzyme Immobilization via Simple and Quantitative Adsorption of Dendronized Polymer-Enzyme Conjugates Inside a Silica Monolith for Enzymatic Flow-Through Reactor Applications

Although many different methods are known for the immobilization of enzymes on solid supports for use in flow-through applications as enzyme reactors, the reproducible immobilization of predetermined amounts of catalytically active enzyme molecules remains challenging. This challenge was tackled using a macro- and mesoporous silica monolith as a support and dendronized polymer-enzyme conjugates. The conjugates were first prepared in an aqueous solution by covalently linking enzyme molecules and either horseradish peroxidase (HRP) or bovine carbonic anhydrase (BCA) along the chains of a water-soluble second-generation dendronized polymer using an established procedure. The obtained conjugates are stable biohybrid structures in which the linking unit between the dendronized polymer and each enzyme molecule is a bisaryl hydrazone (BAH) bond. Quantitative and reproducible enzyme immobilization inside the monolith is possible by simply adding a defined volume of a conjugate solution of a defined enzyme concentration to a dry monolith piece of the desired size. In that way, (i) the entire volume of the conjugate solution is taken up by the monolith piece due to capillary forces and (ii) all conjugates of the added conjugate solution remain stably adsorbed (immobilized) noncovalently without detectable leakage from the monolith piece. The observed flow-through activity of the resulting enzyme reactors was directly proportional to the amount of conjugate used for the reactor preparation. With conjugate solutions consisting of defined amounts of both types of conjugates, the controlled coimmobilization of the two enzymes, namely, BCA and HRP, was shown to be possible in a simple way. Different stability tests of the enzyme reactors were carried out. Finally, the enzyme reactors were applied to the catalysis of a two-enzyme cascade reaction in two types of enzymatic flow-through reactor systems with either coimmobilized or sequentially immobilized BCA and HRP. Depending on the composition of the substrate solution that was pumped through the two types of enzyme reactor systems, the coimmobilized enzymes performed significantly better than the sequentially immobilized ones. This difference, however, is not due to a molecular proximity effect with regard to the enzymes but rather originates from the kinetic features of the cascade reaction used. Overall, the method developed for the controllable and reproducible immobilization of enzymes in the macro- and mesoporous silica monolith offers many possibilities for systematic investigations of immobilized enzymes in enzymatic flow-through reactors, potentially for any type of enzyme.

Silica-based Nanoparticles for Enzyme Immobilization and Delivery

Enzymes play an indispensable role in biosystems, catalyzing a variety of chemical and biochemical reactions with exceptionally high efficiency and selectivity. These features render them uniquely positioned in developing novel catalytic systems and therapeutics. However, their practical application is largely hindered by the vulnerability, low reusability and the inability to overcome the biological barriers of enzymes. Silica-based nanoparticles (SNPs) are a classic family of nanomaterials with tunable physicochemical properties, making them ideal candidates to address the intrinsic shortcomings of natural enzymes. SNPs not only improve the activity and durability of enzymes, but also provide precise spatiotemporal control over their intracellular as well as systemic biodistributions for boosting the catalytic outcome. Herein, the recent progress in SNPs for enzyme immobilization and delivery is summarized. The therapeutic applications, including cancer therapy and bacterial inhibition, are particularly highlighted. Our perspectives in this field, including current challenges and possible future research directions are also provided.

Highly Precise and Sensitive Polymerase Chain Reaction Using Mesoporous Silica-Immobilized Enzymes

A highly precise and sensitive technology that enables DNA amplification/detection from minimal amounts of nucleic acid is expected to find applicability in genetic testing involving small amounts of samples. The use of a free enzyme in conventional DNA amplification techniques, such as the polymerase chain reaction (PCR), frequently causes side reactions (i.e., nonspecific DNA amplification) when ≤10³ substrate DNA molecules are present, thereby preventing selective amplification of the target DNA. To address this issue, we have developed a novel DNA amplification system, mesoporous silica-enhanced PCR (MSE-PCR), which involves the immobilization of a thermostable DNA polymerase from Thermococcus kodakaraensis (KOD DNA polymerase) into highly ordered nanopores of the mesoporous silica to control the reaction environment around the enzyme. In the MSE-PCR system using immobilized KOD DNA polymerase, such nonspecific DNA amplification was remarkably inhibited under the same conditions. Furthermore, the optimization of mesoporous silica pore sizes enabled selective and efficient DNA amplification from DNA substrates at the single-molecule level, i.e., one ten-thousandth of the amount of substrate DNA required for a DNA amplification reaction using a free enzyme. The results obtained in this study have shown that the nanopores of mesoporous silica can inhibit nonspecific reactions in DNA amplification, thereby considerably improving the specificity and sensitivity of the DNA polymerase reaction.

Combining a Genetically Engineered Oxidase with Hydrogen-Bonded Organic Frameworks (HOFs) for Highly Efficient Biocomposites

Enzymes incorporated into hydrogen-bonded organic frameworks (HOFs) via bottom-up synthesis are promising biocomposites for applications in catalysis and sensing. Here, we explored synthetic incorporation of d-amino acid oxidase (DAAO) with the metal-free tetraamidine/tetracarboxylate-based BioHOF-1 in water. N-terminal enzyme fusion with the positively charged module Zbasic2 strongly boosted the loading (2.5-fold; ≈500 mg enzyme gmaterial-1 ) and the specific activity (6.5-fold; 23 U mg-1 ). The DAAO@BioHOF-1 composites showed superior activity with respect to every reported carrier for the same enzyme and excellent stability during catalyst recycling. Further, extension to other enzymes, including cytochrome P450 BM3 (used in the production of high-value oxyfunctionalized compounds), points to the versatility of genetic engineering as a strategy for the preparation of biohybrid systems with unprecedented properties.

Roles of Surfactants in Oriented Immobilization of Cellulase on Nanocarriers and Multiphase Hydrolysis System

Surfactants, especially non-ionic surfactants, play an important role in the preparation of nanocarriers and can also promote the enzymatic hydrolysis of lignocellulose. A broad overview of the current status of surfactants on the immobilization of cellulase is provided in this review. In addition, the restricting factors in cellulase immobilization in the complex multiphase hydrolysis system are discussed, including the carrier structure characteristics, solid-solid contact obstacles, external diffusion resistance, limited recycling frequency, and nonproductive combination of enzyme active centers. Furthermore, promising prospects of cellulase-oriented immobilization are proposed, including the hydrophilic-hydrophobic interaction of surfactants and cellulase in the oil-water reaction system, the reversed micelle system of surfactants, and the possible oriented immobilization mechanism.

Interaction of Aqueous Bovine Serum Albumin with Silica Aerogel Microparticles: Sorption Induced Aggregation

Mesoporous silica aerogels have a wide range of potential applications in biotechnology, the food industry, pharmacy and medicine. Understanding the nature of the interactions of biomolecules with these porous nanostructured materials is essential for achieving optimum performance in the targeted applications. In this study, the well-characterized bovine serum albumin (BSA) was chosen as a model protein to probe protein–aerogel interactions in the solution phase. Aqueous BSA was mixed with suspended silica aerogel microparticles, and the colloid system was monitored on-line by UV–vis spectrophotometry and turbidimetry. The global mathematical analysis of the time-resolved data reveals that the fast sorption of the protein on the aerogel microparticles follows a multistep binding mechanism. The extensive sorption of the protein eventually induces the aggregation of the covered aerogel due to the alteration of the electrical double layer of the particles. The interaction of BSA and silica aerogel is the strongest between pH = 4 and 5, because their native surface charges are the opposite in this pH range, as indicated by their respective zeta potentials.

Assessment of recombinant glutathione-S-transferase (HaGST-8) silica nano-conjugates for effective removal of pesticides

Diverse glutathione-S-transferases (GSTs) are produced by insect pests including Helicoverpa armigera (HaGSTs) for detoxification of insecticides or xenobiotic compounds that they encounter. In an earlier study, the HaGST-8 gene was isolated from H. armigera larvae exposed to pesticide mixtures and the recombinant protein was expressed in the yeast Pichia pastoris. In this investigation, HaGST-8 was successfully immobilized on glutaraldehyde-activated APTES functionalized silica nanoparticles to obtain SiAPT-HaGST-8 nano-conjugates. Although enzyme activity associated with these conjugates was comparable to that of free HaGST-8, the specific activity of the former was found to be 1.25 times higher than the latter. In comparison with the free enzyme (that demonstrated a pH optimum of 9.0), for the nano-conjugates, the pH range was extended between pH 8.0 to 9.0. The optimum temperature for activity of both forms of the enzyme was found to be 30 °C. Stability of the enzyme was improved from 20 d for free HaGST-8 to 30 d for SiAPT-HaGST-8 nano-conjugates. Some loss in GST activity was detected after every reuse cycle of nano-conjugates and in all, 63% reduction was observed after three cycles. When 3 kinds of pesticides (namely, chlorpyrifos, dichlorvos and cypermethrin) were reacted with SiAPT-HaGST-8, more than 80% reduction in levels were observed. On the basis of the results obtained, the use of such silica nanoparticle-based systems for stable enzyme conjugation followed by effective removal of pesticides from aqueous media is envisaged.

Supramolecular Reinforcement of a Large-Pore 2D Covalent Organic Framework

Two-dimensional covalent organic frameworks (2D-COFs) are a class of crystalline porous organic polymers that consist of covalently linked, two-dimensional sheets that can stack together through noncovalent interactions. Here we report the synthesis of a novel COF, called PyCOFamide, which has an experimentally observed pore size that is greater than 6 nm in diameter. This is among the largest pore size reported to date for a 2D-COF. PyCOFamide exhibits permanent porosity and high crystallinity as evidenced by the nitrogen adsorption, powder X-ray diffraction, and high-resolution transmission electron microscopy. We show that the pore size of PyCOFamide is large enough to accommodate fluorescent proteins such as Superfolder green fluorescent protein and mNeonGreen. This work demonstrates the utility of noncovalent structural reinforcement in 2D-COFs to produce larger and persistent pore sizes than previously possible.

Expression, characterization, and immobilization of a novel SGNH esterase Est882 and its potential for pyrethroid degradation

The widely-used pyrethroid pesticides have attracted public attention because of their potentials to cause environmental pollution and toxic effects on non-target organisms. Esterase is a kind of hydrolytic enzyme that can catalyze the cleavage or formation of ester bonds. it plays a pivotal role in the decomposition of pyrethroids and esters containing industrial pollutants through the hydrolysis of ester bonds. Here, a new esterase gene est882 was successfully screened, which encodes Est882, a SGNH family esterase composed of 294 amino acids. It was heterogeneously expressed, identified and immobilized. Multiple sequence alignment showed that Est882 had a typical GDS(X) conserved motif and a catalytic triad composed of Ser79, Asp269 and His275. Phylogenetic analysis showed that Est882 shall belong to a new esterase family. Biochemical characterization demonstrated that the optimum condition was 40°C and pH 9.0. Est882 immobilization was studied with mesoporous silica SBA-15 as the carrier and found to significantly improve the tolerance and stability of Est882. Its optimum pH increased to 10.0 and stabilized within pH 8.0-11.0. Free Est882 can effectively degrade various pyrethroids within 30 min, with a degradation rate above 80%. The immobilized Est882 yet degraded more than 70% of pyrethroids within 30 min. The present study indicated that Est882 has outstanding potential in bioremediation of a pyrethroid-polluted environment. These characteristics endow Est882 with potential values in various industrial applications and hydrolysis of pyrethroid residues.

Protein Adsorption onto Modified Porous Silica by Single and Binary Human Serum Protein Solutions

Typical porous silica (SBA-15) has been modified with pore expander agent (1,3,5-trimethylbenzene) and fluoride-species to diminish the length of the channels to obtain materials with different textural properties, varying the Si/Zr molar ratio between 20 and 5. These porous materials were characterized by X-ray Diffraction (XRD), N2 adsorption/desorption isotherms at -196 °C and X-ray Photoelectron Spectroscopy (XPS), obtaining adsorbent with a surface area between 420-337 m2 g-1 and an average pore diameter with a maximum between 20-25 nm. These materials were studied in the adsorption of human blood serum proteins (human serum albumin-HSA and immunoglobulin G-IgG). Generally, the incorporation of small proportions was favorable for proteins adsorption. The adsorption data revealed that the maximum adsorption capacity was reached close to the pI. The batch purification experiments in binary human serum solutions showed that Si sample has considerable adsorption for IgG while HSA adsorption is relatively low, so it is possible its separation.

Silica-rich regenerated cellulose fibers enabled by delayed dissolution of silica nanoparticles in strong alkali using zinc oxide

Silica nanoparticles (SNPs) dissolve in alkaline media, which limits their use in certain applications. Here, we report a delayed dissolution of SNPs in strong alkali induced by zinc oxide (ZnO), an additive which also limits gelation of alkaline cellulose solutions. This allows incorporating high solid content of silica (30 wt%) in cellulose solutions with retention of their predominant viscous behavior long enough (ca. 180 min) to enable fiber wet spinning. We show that without addition of ZnO, silica dissolves completely, resulting in strong gelation of cellulose solutions that become unsuitable for wet spinning. With an increase of silica concentration, gelation of the solutions occurs faster. Employing ZnO, silica-rich regenerated cellulose fibers were successfully spun, possessing uniform cross sections and smooth surface structure without defects. These findings are useful in advancing the development of functional man-made cellulose fibers with incorporated silica, e.g., fibers with flame retardant or self-cleaning properties.

Boric Acid-Fueled ATP Synthesis by Fo F1 ATP Synthase Reconstituted in a Supramolecular Architecture

Significant strides toward producing biochemical fuels have been achieved by mimicking natural oxidative and photosynthetic phosphorylation. Here, different from these strategies, we explore boric acid as a fuel for tuneable synthesis of energy-storing molecules in a cell-like supramolecular architecture. Specifically, a proton locked in boric acid is released in a modulated fashion by the choice of polyols. As a consequence, controlled proton gradients across the lipid membrane are established to drive ATP synthase embedded in the biomimetic architecture, which facilitates tuneable ATP production. This strategy paves a unique route to achieve highly efficient bioenergy conversion, holding broad applications in synthesis and devices that require biochemical fuels.

PEG-Coated Large Mesoporous Silicas as Smart Platform for Protein Delivery and Their Use in a Collagen-Based Formulation for 3D Printing

Silica-based mesoporous systems have gained great interest in drug delivery applications due to their excellent biocompatibility and high loading capability. However, these materials face challenges in terms of pore-size limitations since they are characterized by nanopores ranging between 6-8 nm and thus unsuitable to host large molecular weight molecules such as proteins, enzymes and growth factors (GFs). In this work, for an application in the field of bone regeneration, large-pore mesoporous silicas (LPMSs) were developed to vehicle large biomolecules and release them under a pH stimulus. Considering bone remodeling, the proposed pH-triggered mechanism aims to mimic the release of GFs encased in the bone matrix due to bone resorption by osteoclasts (OCs) and the associated pH drop. To this aim, LPMSs were prepared by using 1,3,5-trimethyl benzene (TMB) as a swelling agent and the synthesis solution was hydrothermally treated and the influence of different process temperatures and durations on the resulting mesostructure was investigated. The synthesized particles exhibited a cage-like mesoporous structure with accessible pores of diameter up to 23 nm. LPMSs produced at 140 °C for 24 h showed the best compromise in terms of specific surface area, pores size and shape and hence, were selected for further experiments. Horseradish peroxidase (HRP) was used as model protein to evaluate the ability of the LPMSs to adsorb and release large biomolecules. After HRP-loading, LPMSs were coated with a pH-responsive polymer, poly(ethylene glycol) (PEG), allowing the release of the incorporated biomolecules in response to a pH decrease, in an attempt to mimic GFs release in bone under the acidic pH generated by the resorption activity of OCs. The reported results proved that PEG-coated carriers released HRP more quickly in an acidic environment, due to the protonation of PEG at low pH that catalyzes polymer hydrolysis reaction. Our findings indicate that LPMSs could be used as carriers to deliver large biomolecules and prove the effectiveness of PEG as pH-responsive coating. Finally, as proof of concept, a collagen-based suspension was obtained by incorporating PEG-coated LPMS carriers into a type I collagen matrix with the aim of designing a hybrid formulation for 3D-printing of bone scaffolds.

Lipase from Rhizopus oryzae R1: in-depth characterization, immobilization, and evaluation in biodiesel production

Background

Rhizopus species is among the most well-known lipase producers, and its enzyme is suitable for use in many industrial applications. Our research focuses on the production of lipase utilizing waste besides evaluating its applications.

Results

An extracellular lipase was partially purified from the culture broth of Rhizopus oryzae R1 isolate to apparent homogeneity using ammonium sulfate precipitation followed by desalting via dialysis. The partially purified enzyme was non-specific lipase and the utmost activity was recorded at pH 6, 40 °C with high stability for 30 min. The constants K_m and V_max, calculated from the Lineweaver-Burk plot, are 0.3 mg/mL and 208.3 U/mL, respectively. Monovalent metal ions such as Na⁺ (1 and 5 mM) and K⁺ (5 mM) were promoters of the lipase to enhance its activity with 110, 105.5, and 106.5%, respectively. Chitosan was used as a perfect support for immobilization via both adsorption and cross-linking in which the latter method attained immobilization efficiency of 99.1% and reusability of 12 cycles. The partially purified enzyme proved its ability in forming methyl oleate (biodiesel) through the esterification of oleic acid and transesterification of olive oil.

Conclusion

The partially purified and immobilized lipase from Rhizopus oryzae R1 approved excellent efficiency, reusability, and a remarkable role in detergents and biodiesel production.

Improved biocatalytic cascade conversion of CO2 to methanol by enzymes Co-immobilized in tailored siliceous mesostructured cellular foams

CO2 can be enzymatically reduced to methanol in a cascade reaction involving three enzymes: formate-, formaldehyde- and alcohol dehydrogenase (FateDH, FaldDH, ADH).

Structural Characterization of Proteins Adsorbed at Nanoporous Materials

A nanoporous material has been applied for the development of functional nanobiomaterials by utilizing its uniform pore structure and large adsorption capacity. The structure and stability of biomacromolecules, such as peptide, oligonucleotide, and protein, are primary factors to govern the performance of nanobiomaterials, so that their direct characterization methodologies are in progress. In this review, we focus on recent topics in the structural characterization of protein molecules adsorbed at a nanoporous material with uniform meso-sized pores. The thermal stabilities of the adsorbed proteins are also summarized to discuss whether the structure of the adsorbed protein molecules can be stabilized or not.

Process intensification using immobilized enzymes for the development of white biotechnology

Process intensification of biocatalysed reactions using different techniques such as microwaves, ultrasound, hydrodynamic cavitation, ionic liquids, microreactors and flow chemistry in various industries is critically analysed and future directions provided.

Nanostructured materials for harnessing the power of horseradish peroxidase for tailored environmental applications

High catalytic efficiency, stereoselectivity, and sustainability outcomes of enzymes entice chemists for considering biocatalytic transformations to supplant conventional synthetic routes. As a green and versatile enzyme, horseradish peroxidase (HRP)-based enzymatic catalysis has been widely employed in a range of biological and chemical transformation processes. Nevertheless, like many other enzymes, HRP is likely to denature or destabilize in harsh realistic conditions due to its intrinsic fragile nature, which results in inevitably shortened lifespan and immensely high bioprocess cost. Enzyme immobilization has proven as a prospective strategy for improving their biocatalytic performance in continuous industrial processes. Nanostructured materials with huge accessible surface area, abundant porous structures, exceptional functionalities, and high chemical and mechanical stability have recently garnered intriguing research interests as novel kinds of supporting matrices for HRP immobilization. Many reported immobilized biocatalytic systems have demonstrated high catalytic performances than that to the free form of enzymes, such as enhanced enzyme efficiency, selectivity, stability, and repeatability due to the protective microenvironments provided by nanostructures. This review delineates an updated overview of HRP immobilization using an array of nanostructured materials. Furthermore, the general physicochemical aspects, improved catalytic attributes, and the robust practical implementations of engineered HRP-based catalytic cues are also discussed with suitable examples. To end, concluding remarks, challenges, and worthy suggestions/perspectives for future enzyme immobilization are also given.

Efficient production of γ-aminobutyric acid by glutamate decarboxylase immobilized on an amphiphilic organic-inorganic hybrid porous material

A novel organic-inorganic hybrid porous material (KCS-2), containing both lipophilic and hydrophilic nanospaces to mimic a lipid bilayer, was utilized as an immobilization support and reaction accelerator for glutamate decarboxylase (GADβ). Upon evaluation of the adsorption of GADβ on KCS-2, the amount of immobilization was found to be approximately four times higher than that on non-porous silica, and a comparable adsorbability to mesoporous silica was observed. Following γ-aminobutyric acid (GABA) production by the decarboxylation of l-glutamic acid using these immobilized enzymes, the enzymatic activity of the GADβ-KCS-2 composite was found to be significantly higher than that of the free enzyme. In contrast, the activity of the more common GADβ-mesoporous silica composite decreased. Furthermore, the enzymatic activity of the GADβ-KCS-2 composite was superior to those of the un-immobilized free enzyme and the amorphous material itself over a wide temperature range. Thereby, these findings suggest that the amphiphilic nanospace of KCS-2 is suitable as a stable enzyme immobilization field and reaction acceleration field under such conditions. In addition, the durability of the immobilized enzyme was examined in terms of GABA production, with approximately 20% activity retention being observed after 10 cycles using KCS-2. Such durability was not observed for the non-porous silica material due to enzyme desorption.