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.

A Potentially Versatile Enzyme Sensor Platform: Enzyme-Loaded, Tagged, Porous Polymeric Nanocapsules

Enzymes are essential to life and indispensable in a wide range of industries (food, pharmaceutical, medical, biosensing, etc.); however, a significant shortcoming of these fragile biological catalysts is their poor stability. To address this challenge, a variety of immobilization methods have been described to enhance the enzyme's stability. These immobilization methods generally are specific to an individual enzyme or optimal for a particular application. The aim of this study is to explore the utility of porous, indicator moiety-tagged, polymeric nanocapsules (NCs) for the encapsulation of enzymes and measurement of the enzyme's substrate. As a model enzyme, glucose oxidase (GOx) is used. The GOx enzyme-loaded, fluorophore-tagged NCs were synthesized by using self-assembled surfactant vesicle templates. To show that the biological activity of GOx is preserved during entrapment, the rate of the GOx enzyme catalyzed reaction was measured. To evaluate the protective features of the porous NCs, the encapsulated GOx enzyme activity was followed in the presence of hydrolytic enzymes. During the encapsulation of GOx and the purification of the GOx-loaded NCs, the GOx activity decayed less than 10%, and up to 30% of the encapsulated GOx activity could be retained for 3-5 days in the presence of hydrolytic enzymes. In support of the potentially unique advantages of the enzyme-loaded NCs, as a proof-of-concept example, the fluorophore-tagged, GOx-loaded NCs were used for the determination of glucose in the concentration range between 18 and 162 mg/dL and for imaging the distribution of glucose concentration in imaging experiments.

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.

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.

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.

Design of enzyme@metal organic framework composites with thermo-responsivity for colourimetric detection of glucose

Enzyme immobilization on metal-organic frameworks (MOFs) has interested researchers in recent decades due to the outstanding characteristics of MOFs. However, despite some enzyme@MOF composites exhibiting better tolerance, stability and catalysis than free enzymes, boosting the catalytic performance of stimuli-responsive polymer-grafted MOFs composites remains a challenging task. Herein, a glucose oxidase (GOx)-horseradish peroxidase (HRP)@MOF (UiO-66-NH2, U)@polymer composite with tunable catalytic ability was constructed by modification with thermo-responsive poly(N-isopropylacrylamide) (PN) via a surface-selective post-synthetic protocol. Temperature increases changed the PN-based soft armour from a "stretch" to a "coil" conformation on the MOF surface, resulting in the confinement effect and boosting the catalytic performance of the GOx-HRP@U@PN composites. Compared with its maximum catalytic reaction rate at 25 °C, the proposed composites showed 18-fold improvement in catalytic performance at 37 °C. Additionally, a colourimetric method for serum glucose analysis was developed using a GOx-HRP-based catalytic cascade reaction with a linear range from 0.1 to 2.0 mM and a low detection limit of 0.03 mM. Remarkably, the surface PN-shell-based soft armour proved to be the key factor for enhancing the catalytic performance of the as-designed composites. The co-immobilization of GOx-HRP onto the thermo-responsive U@PN surface provides a new approach for the development of highly sensitive colourimetric glucose sensing protocols.

An Up-to-Date Review on the Remediation of Dyes and Phenolic Compounds from Wastewaters Using Enzymes Immobilized on Emerging and Nanostructured Materials: Promises and Challenges

Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Immobilization of Aspergillus sp. laccase on hierarchical silica MFI zeolite with embedded macropores

Laccase from Aspergillus sp. (LC) was immobilized on functionalized silica hierarchical (microporous-macroporous) MFI zeolite (ZMFI). The obtained immobilized biocatalyst (LC#ZMFI) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (ATR-FTIR), N₂ adsorption/desorption isotherms, solid-state NMR spectroscopy and thermogravimetric analysis (TGA) confirming the chemical anchoring of the enzyme to the zeolitic support. The optimal pH, kinetic parameters (K_M and V_max), specific activity, as well as both storage and operational stability of LC#ZMFI were determined. The LC#ZMFI K_M and V_max values amount to 10.3 µM and 0.74 µmol·mg^-1 min^-1, respectively. The dependence of specific activity on the pH for free and immobilized LC was investigated in the pH range of 2-7, The highest specific activity was obtained at pH = 3 for both free LC and LC#ZMFI. LC#ZMFI retained up to 50 % and 30 % of its original activity after storage of 21 and 30 days, respectively. Immobilization of laccase on hierarchical silica MFI zeolite allows to carry out the reaction under acidic pH values without affecting the support structure.

Valorization of Waste Cooking Oil into Biodiesel via Bacillus stratosphericus Lipase Amine-Functionalized Mesoporous SBA-15 Nanobiocatalyst

In this study, evaporation-induced self-assembly was applied to prepare amine-functionalized nano-silica (NH2-Pr-SBA-15). That was simply used to immobilize Bacillus stratosphericus PSP8 lipase (E–NH2–Pr-SBA-15), producing a nanobiocatalyst with good stability under vigorous shaking and a maximum lipase activity of 45 ± 2 U/mL. High-resolution X-ray diffractometer, Fourier transform infrared spectroscopy, N2 adsorption-desorption, field-emission scanning electron, and high-resolution transmission electron microscopic analyses proved the successful SBA-15 functionalization and enzyme immobilization. Response surface methodology based on a 1/2 fraction-three-levels face center composite design was applied to optimize the biodiesel transesterification process. This expressed efficient percentage conversion (97.85%) and biodiesel yield (97.01%) under relatively mild operating conditions: 3.12 : 1 methanol to oil ratio, 3.08 wt.% E–NH2–Pr-SBA-15 loading, 48.6°C, 3.19 h at a mixing rate of 495.53 rpm. E–NH2–Pr-SBA-15 proved to have a long lifetime, operational stability, and reusability.

Biocatalysts Synthesized with Lipase from Pseudomonas cepacia on Glycol-Modified ZIF-8: Characterization and Utilization in the Synthesis of Green Biodiesel

This research presents results on the production of biodiesel from the transesterification of acylglycerides present in palm oil, using the biocatalysts ZIF-8-PCL and Gly@ZIF-8-PCL synthesized by immobilization of Pseudomonas Cepacia Lipase as catalytic materials and using pure ZIF-8 and Gly@ZIF-8 (modified ZIF-8) as supports. The Gly@ZIF-8 carbonaceous material was prepared by wet impregnation of ZIF-8 with ethylene glycol as the carbon source, and then thermally modified. The calcination conditions were 900 °C for two hours with a heating rate of 7 °C/min in an inert atmosphere. A textural characterization was performed, and results showed superficial changes of materials at the microporous and mesoporous levels for the Gly@ZIF-8 material. Both the starting materials and biocatalysts were characterized by infrared spectroscopy (FTIR) and Raman spectroscopy. During the transesterification, using the two biocatalysts (ZIF-8-PCL and Gly@ZIF-8-PCL), two supernatant liquids were generated which were characterized by infrared spectroscopy (FTIR), gas chromatography coupled to mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). The results show that the two routes of synthesis of supports from ZIF-8 will be configured as effective methods for the generation of effective biocatalysts for biodiesel production.

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.

Confining enzymes in porous organic frameworks: from synthetic strategy and characterization to healthcare applications

Enzymes are a class of natural catalysts with high efficiency, specificity, and selectivity unmatched by their synthetic counterparts and dictate a myriad of reactions that constitute various cascades in living cells. The development of suitable supports is significant for the immobilization of structurally flexible enzymes, enabling biomimetic transformation in the extracellular environment. Accordingly, porous organic frameworks, including metal organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), have emerged as ideal supports for the immobilization of enzymes because of their structural features including ultrahigh surface area, tailorable porosity, and versatile framework compositions. Specially, organic framework-encased enzymes have shown significant enhancement in stability and reusability, and their tailorable pore opening provides a gatekeeper-like effect for guest sieving, which is beneficial for mimicking intracellular biocatalysis processes. This immobilization technique brings new insight into the development of next-generation enzyme materials and shows huge potential in healthcare applications, such as biomarker diagnosis, biostorage, and cancer and antibacterial therapies. In this review, we describe the state-of-the-art strategies for the structural immobilization of enzymes using the well-explored MOFs and burgeoning COFs and HOFs as scaffolds, with special emphasis on how these porous framework-confined technologies can provide a favorable microenvironment for mimicking natural biocatalysis. Subsequently, advanced characterization techniques for enzyme conformation, the effect of the confined microenvironment on the activity of enzymes, and the emerging healthcare applications will be surveyed.

Immobilized glucose oxidase on hierarchically porous COFs and integrated nanozymes: a cascade reaction strategy for ratiometric fluorescence sensors

Covalent organic frameworks (COFs) with uniform porosity, good stability, and desired biocompatibility can function as carriers of immobilized enzymes. However, the obstructed pores or partially obstructed pores have hindered their applicability after loading enzymes. In this study, the hierarchical COFs were prepared as an ideal support to immobilize glucose oxidase (GOD) and obtain GOD@COF. The hierarchical porosity and porous structures of COFs provided sufficient sites to immobilize GOD and increased the rate of diffusion of substrate and product. Moreover, N,Fe-doped carbon dots (N,Fe-CDs) with peroxidase-like activity were introduced to combine with GOD@COF to construct an enzyme-mediated cascade reaction, which is the basis of the sensor GOD@COF/N,Fe-CDs. The sensor has been successfully built and applied to detect glucose. The limit of detection was 0.59 μM for determining glucose with the proposed fluorescence sensor. The practicability was illustrated by detecting glucose in human serum and saliva samples with satisfactory recoveries. The proposed sensor provided a novel strategy that introduced COF-immobilized enzymes for cascade reactions in biosensing and clinical diagnosis.

Harnessing the Structural and Functional Diversity of Protein Filaments as Biomaterial Scaffolds

The natural ability of many proteins to polymerize into highly structured filaments has been harnessed as scaffolds to align functional molecules in a diverse range of biomaterials. Protein-engineering methodologies also enable the structural and physical properties of filaments to be tailored for specific biomaterial applications through genetic engineering or filaments built from the ground up using advances in the computational prediction of protein folding and assembly. Using these approaches, protein filament-based biomaterials have been engineered to accelerate enzymatic catalysis, provide routes for the biomineralization of inorganic materials, facilitate energy production and transfer, and provide support for mammalian cells for tissue engineering. In this review, we describe how the unique structural and functional diversity in natural and computationally designed protein filaments can be harnessed in biomaterials. In addition, we detail applications of these protein assemblies as material scaffolds with a particular emphasis on applications that exploit unique properties of specific filaments. Through the diversity of protein filaments, the biomaterial engineer's toolbox contains many modular protein filaments that will likely be incorporated as the main structural component of future biomaterials.

Near-Infrared-II Plasmonic Trienzyme-Integrated Metal-Organic Frameworks with High-Efficiency Enzyme Cascades for Synergistic Trimodal Oncotherapy

Natural enzyme-based catalytic cascades hold great promise for cancer therapy, but their clinical utility is greatly hindered by the loss of their functions during in vivo delivery. Herein, a plasmonic trienzyme-integrated metal-organic framework (plasEnMOF) nanoplatform with high-efficiency enzyme cascades is reported for synergistic starvation, chemodynamic, and plasmonic hyperthermia trimodal therapy of hypoxic tumors. These plasEnMOFs are created with encapsulation of near-infrared-II (NIR-II) plasmonic Au nanorods and natural enzymes-catalase (CAT), glucose oxidase (GOx), and horseradish peroxidase (HRP) within zeolitic imidazolate framework-8 (ZIF-8) MOFs. As a trienzyme cascade system, the plasEnMOFs effectively deplete intratumoral glucose and generate toxic reactive oxygen species (ROS) for starvation therapy and chemodynamic therapy (CDT) combined with the plasmonic hyperthermia therapy (PHT). The enhanced glucose consumption and ROS generation by the NIR-II plasmonic photothermal effect are also demonstrated. The improved chemo- and thermotolerance of the encapsulated natural enzymes within the protective ZIF-8 MOFs are evidenced. With the integrated enzyme cascades and NIR-II photothermal effects, these plasEnMOFs are demonstrated with exceptional therapeutic effects on 4T1 xenograft tumors through the combined starvation/CDT/PHT therapy. This work highlights the superiority of natural enzyme cascade systems integrated in plasmonic MOFs for high-efficiency enzymatic cancer therapy.

Stimuli-Responsive Transformable Supramolecular Nanotubes

Supramolecular nanotubes produced by self-assembly of organic molecules can have unique structural features such as a one-dimensional morphology with no branching, distinguishable inner and outer surfaces and membrane walls, or a structure that is hollow and has a high aspect ratio. Incorporation of functional groups that respond to external chemical or physical stimuli into the constituent organic molecules of supramolecular nanotubes allows us to drastically change the structure of the nanotubes by applying such stimuli. This ability affords an array of controllable approaches for the encapsulation, storage, and release of guest compounds, which is expected to be useful in the fields of physics, chemistry, biology, and medicine. In this article, I review the supramolecular nanotubes developed by our group that exhibit morphological transformations in response to pH, chemical reaction, light, temperature, or moisture.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

Rapid sample preparation workflow based on enzymatic nanoreactors for potential serum biomarker discovery in pancreatic cancer

Mass spectrometry (MS)-based proteomics have been extensively applied in clinical practice to discover potential protein and peptide biomarkers. However, the traditional sample pretreatment workflow remains labor-intensive and time-consuming, which limits the application of MS-based proteomic biomarker discovery studies in a high throughput manner. In the current work, we improved the previously reported procedure of the simple and rapid sample preparation methods (RSP) by introducing macroporous ordered siliceous foams (MOSF), namely RSP-MOSF. With the aid of MOSF, we further reduced the digestion time to 10 min, facilitating the whole sample handling process within 30 min. Combining with 30 min direct data independent acquisition (DIA) of LC-MS/MS, we accomplished a serum sample analysis in 1 h. Comparing with the RSP method, the performance of protein and peptide identification, quantitation, as well as the reproducibility of RSP-MOSF is comparable or even outperformed the RSP method. We further applied this workflow to analyze serum samples for potential candidate biomarker discovery of pancreatic cancer. Overall, 576 serum proteins were detected with 41 proteins significantly changed, which could serve as potential biomarkers for pancreatic cancer. Additionally, we evaluated the performance of RSP-MOSF method in a 96-well plate format which demonstrated an excellent reproducibility of the analysis. These results indicated that RSP-MOSF method had the potential to be applied on an automatic platform for further scaled analysis.

Biocatalytic Metal-Organic Framework: Promising Materials for Biosensing

The high-efficient and specific catalysis of enzyme allow it to recognize a myriad of substrate that impels the biosensing. Nevertheless, the fragility of natural enzymes severely restricts their practical applications. Metal-organic frameworks (MOFs) with porous network and attractive functions have been intelligently employed as supports to encase enzymes for protecting them against hash environments. More importantly, the customizable construction and composition affords the intrinsic enzyme-like activity of some MOFs (known as nanozymes), which provides an alternative guideline to construct robust enzymes mimics. Herein, this review will introduce the concept of these biocatalytic MOFs, with the special emphasis on how the biocatalytic processes operated in these MOFs materials can reverse the plight of native enzymes-based biosensing. In addition, the present challenges and future outlooks in this research field are briefly put forward.

Immobilisation and stabilisation of glycosylated enzymes on boronic acid-functionalised silica nanoparticles

We report a method of glycosylated enzymes' surface immobilisation and stabilisation. The enzyme is immobilised at the surface of silica nanoparticles through the reversible covalent binding of vicinal diols of the enzyme glycans with a surface-attached boronate derivative. A soft organosilica layer of controlled thickness is grown at the silica surface, entrapping the enzyme and thus avoiding enzyme leaching. We demonstrate that this approach results not only in high and durable activity retention but also enzyme stabilisation.

De Novo Approach to Encapsulating Biocatalysts into Synthetic Matrixes: From Enzymes to Microbial Electrocatalysts

Biocatalysts hold great promise in chemical and electrochemical reactions. However, biocatalysts are prone to inhospitable physiochemical conditions. Encapsulating biocatalysts into a synthetic host matrix can improve their stability and activity, and broaden their operational conditions. In this Review, we summarize the emerging de novo approaches to encapsulating biocatalysts into synthetic matrixes. Here, de novo means that embedding of biocatalysts and construction of matrixes take place simultaneously. We discuss the advantages and limitations of the de novo approach. On the basis of the nature of the biocatalysts and the synthetic frameworks, we specifically focus on two aspects: (1) encapsulation of enzymes (in vitro) in metal-organic frameworks and (2) encapsulation of microbial electrocatalysts (in vivo) on the electrode. For both cases, we discuss how the encapsulation improves biocatalysts' performance (stability, viability, activity, and etc.). We also highlight the benefit of encapsulation in facilitating the transport of charge carriers in microbial electrocatalysis.

Recent advances in carbon nanotubes-based biocatalysts and their applications

Enzymes have been incorporated into a wide variety of fields and industries as they catalyze many biochemical and chemical reactions. The immobilization of enzymes on carbon nanotubes (CNTs) for generating nano biocatalysts with high stability and reusability is gaining great attention among researchers. Functionalized CNTs act as excellent support for effective enzyme immobilization. Depending on the application, the enzymes can be tailored using the various surface functionalization techniques on the CNTs to extricate the desirable characteristics. Aiming at the preparation of efficient, stable, and recyclable nanobiocatalysts, this review provides an overview of the methods developed to immobilize the various enzymes. Various applications of carbon nanotube-based biocatalysts in water purification, bioremediation, biosensors, and biofuel cells have been comprehensively reviewed.

Enzyme immobilization on metal organic frameworks: Laccase from Aspergillus sp. is better adapted to ZIF-zni rather than Fe-BTC

Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic frameworks through a one-pot synthesis carried out under mild conditions (room temperature and aqueous solution). The Fe-BTC, ZIF-zni MOFs, and the LC@Fe-BTC, LC@ZIF-zni immobilized LC samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The kinetic parameters (K_M and V_max) and the specific activity of the free and immobilized laccase were determined. Immobilized LCs resulted in a lower specific activity compared with that of the free LC (7.7 µmol min^-1 mg^-1). However, LC@ZIF-zni was almost 10 times more active than LC@Fe-BTC (1.32 µmol min^-1 mg^-1 vs 0.17 µmol min^-1 mg^-1) and only 5.8 times less active than free LC. The effect of enzyme loading showed that LC@Fe-BTC had an optimal loading of 45.2 mg g^-1, at higher enzyme loadings the specific activity decreased. In contrast, the specific activity of LC@ZIF-zni increased linearly over the loading range investigated. The storage stability of LC@Fe-BTC was low with a significant decrease in activity after 5 days, while LC@ZIF retained up to 50% of its original activity after 30 days storage. The difference in activity and stability between LC@Fe-BTC and LC@ZIF-zni is likely due to release of Fe³⁺ and the low stability of Fe-BTC MOF. Together, these results indicate that ZIF-zni is a superior support for the immobilization of laccase.

Immobilization of Enzymes by Polymeric Materials

Enzymes are the highly efficient biocatalyst in modern biotechnological industries. Due to the fragile property exposed to the external stimulus, the application of enzymes is highly limited. The immobilized enzyme by polymer has become a research hotspot to empower enzymes with more extraordinary properties and broader usage. Compared with free enzyme, polymer immobilized enzymes improve thermal and operational stability in harsh environments, such as extreme pH, temperature and concentration. Furthermore, good reusability is also highly expected. The first part of this study reviews the three primary immobilization methods: physical adsorption, covalent binding and entrapment, with their advantages and drawbacks. The second part of this paper includes some polymer applications and their derivatives in the immobilization of enzymes.

Engineering of a Novel, Magnetic, Bi-Functional, Enzymatic Nanobiocatalyst for the Highly Efficient Synthesis of Enantiopure (R)-3-quinuclidinol

Ni2+-NTA-boosted magnetic porous silica nanoparticles (Ni@MSN) to serve as ideal support for bi-functional enzyme were fabricated for the first time. The versatility of this support was validated by one-step purification and immobilization of bi-functional enzyme MLG consisting of 3-Quinuclidinone reductase and glucose dehydrogenase, which can simultaneously catalyze both carbonyl reduction and cofactor regeneration, to fabricate an artificial bi-functional nanobiocatalyst (namely, MLG-Ni@MSN). The enzyme loading of 71.7 mg/g support and 92.7% immobilization efficiency were obtained. Moreover, the immobilized MLG showed wider pH and temperature tolerance and greater storage stability than free MLG under the same conditions. The nanosystem was employed as biocatalyst to accomplish the 3-quinuclidinone (70 g/L) to (R)-3-quinuclidinol biotransformation in 100% conversion yield with >99% selectivity within 6 h and simultaneous cofactor regeneration. Furthermore, the immobilized MLG retained up to 80.3% (carbonyl reduction) and 78.0% (cofactor regeneration) of the initial activity after being recycled eight times. In addition, the MLG-Ni@MSN system exhibited almost no enzyme leaching during biotransformation and recycling. Therefore, we have reason to believe that the Ni@MSN support gave great promise for constructing a new biocatalytic nanosystem with multifunctional enzymes to achieve some other complex bioconversions.

Multi-enzyme co-immobilized nano-assemblies: Bringing enzymes together for expanding bio-catalysis scope to meet biotechnological challenges

Co-immobilization of multi-enzymes has emerged as a promising concept to design and signify bio-catalysis engineering. Undoubtedly, the existence and importance of basic immobilization methods such as encapsulation, covalent binding, cross-linking, or even simple adsorption cannot be ignored as they are the core of advanced co-immobilization strategies. Different strategies have been developed and deployed to green the twenty-first century bio-catalysis. Moreover, co-immobilization of multi-enzymes has successfully resolved the limitations of individual enzyme loaded constructs. With an added value of this advanced bio-catalysis engineering platform, designing, and fabricating co-immobilized enzymes loaded nanostructure carriers to perform a particular set of reactions with high catalytic turnover is of supreme interest. Herein, we spotlight the emergence of co-immobilization strategies by bringing multi-enzymes together with various types of nanocarriers to expand the bio-catalysis scope. Following a brief introduction, the first part of the review focuses on multienzyme co-immobilization strategies, i.e., random co-immobilization, compartmentalization, and positional co-immobilization. The second part comprehensively covers four major categories of nanocarriers, i.e., carbon based nanocarriers, polymer based nanocarriers, silica-based nanocarriers, and metal-based nanocarriers along with their particular examples. In each section, several critical factors that can affect the performance and successful deployment of co-immobilization of enzymes are given in this work.

Functionalized Mesoporous Thin Films for Biotechnology

Mesoporous materials bear great potential for biotechnological applications due to their biocompatibility and versatility. Their high surface area and pore interconnection allow the immobilization of molecules and their subsequent controlled delivery. Modifications of the mesoporous material with the addition of different chemical species, make them particularly suitable for the production of bioactive coatings. Functionalized thin films of mesoporous silica and titania can be used as scaffolds with properties as diverse as promotion of cell growth, inhibition of biofilms formation, or development of sensors based on immobilized enzymes. The possibility to pattern them increase their appeal as they can be incorporated into devices and can be tailored both with respect to architecture and functionalization. In fact, selective surface manipulation is the ground for the fabrication of advanced micro devices that combine standard micro/nanofluids with functional materials. In this review, we will present the advantages of the functionalization of silica and titania mesoporous materials deposited in thin film. Different functional groups used to modify their properties will be summarized, as well as functionalization methods and some examples of applications of modified materials, thus giving an overview of the essential role of functionalization to improve the performance of such innovative materials.

Tailoring metal-organic frameworks-based nanozymes for bacterial theranostics

Nanozymes are next-generation artificial enzymes having distinguished features such as cost-effective, enhanced surface area, and high stability. However, limited selectivity and moderate activity of nanozymes in the biochemical environment hindered their usage and encouraged researchers to seek alternative catalytic materials. Recently, metal-organic frameworks (MOFs) characterized by distinct crystalline porous structures with large surface area, tunable pores, and uniformly dispersed active sites emerged, that filled the gap between natural enzymes and nanozymes. Moreover, by selecting suitable metal ions and organic linkers, MOFs can be designed for effective bacterial theranostics. In this review, we briefly presented the design and fabrication of MOFs. Then, we demonstrated the applications of MOFs in bacterial theranostics and their safety considerations. Finally, we proposed the major obstacles and opportunities for further development in research on the interface of nanozymes and MOFs. We expect that MOFs based nanozymes with unique physicochemical and intrinsic enzyme-mimicking properties will gain broad interest in both fundamental research and biomedical applications.

Enzymatic Cascade Reactions Mediated by Highly Efficient Biomimetic Quasi Metal-Organic Frameworks

The integration of chemo- and enzymatic catalysis for effective multistep cascades has presented critical challenges for decades. In this work, the biomimetic quasi NH₂-MIL-101 (qNM) with highly efficient peroxidase-like activity was synthesized via a palmitic acid-induced strategy followed by pyrolysis. The effects of the amount of palmitic acid and calcination temperature on the synthesis of qNM were optimized. It was found that qNM was an excellent catalyst for oxidations of various peroxidase substrates, and a possible mechanism was proposed, i.e., the presence of Fe^II species in qNM was responsible for its excellent activity, which facilitated the transition between Fe^II and Fe^III species to produce more hydroxyl radicals by H₂O₂ decomposition. The qNM served as the potential matrix for enzyme immobilization through a cross-linking method, and kinetic studies revealed that the catalytic efficiency (k_cat/K_m) for the immobilized GOx (23.7 mM^-1 s^-1) is comparable to that of free GOx (26.9 mM^-1 s^-1). The immobilized GOx also showed improved stability against high temperatures and organic solvents compared to free GOx, and analysis of the secondary structure of GOx indicated that the improved stability resulted from enzyme rigidity by the intense covalent linkage with qNM. Furthermore, qNM contributed its biomimetic activity to cooperate with a single enzyme (GOx) or two enzymes (β-Gal and GOx) for the enzymatic cascade reactions. Compared with the mixture of each component in the solution, the combination of the single-enzyme system (GOx) or the two-enzyme system (β-Gal and GOx) in qNM achieved 2.67-fold and 1.83-fold enhancements in the activity of catalytic cascades, respectively. This study provides new insights into the construction of effective and synergistic cascade reactions by integrating biomimetic MOF with natural enzyme, which holds potential for applications in biotechnology and ecofriendly and biomimetic catalysis.

Immobilization of formate dehydrogenase in metal organic frameworks for enhanced conversion of carbon dioxide to formate

Hydrogenation of carbon dioxide (CO₂) to formic acid by the enzyme formate dehydrogenase (FDH) is a promising technology for reducing CO₂ concentrations in an environmentally friendly manner. However, the easy separation of FDH with enhanced stability and reusability is essential to the practical and economical implementation of the process. To achieve this, the enzyme must be used in an immobilized form. However, conventional immobilization by physical adsorption is prone to leaching, resulting in low stability. Although other immobilization methods (such as chemical adsorption) enhance stability, they generally result in low activity. In addition, mass transfer limitations are a major problem with most conventional immobilized enzymes. In this review paper, the effectiveness of metal organic frameworks (MOFs) is assessed as a promising alternative support for FDH immobilization. Kinetic mechanisms and stability of wild FDH from various sources were assessed and compared to those of cloned and genetically modified FDH. Various techniques for the synthesis of MOFs and different immobilization strategies are presented, with special emphasis on in situ and post synthetic immobilization of FDH in MOFs for CO₂ hydrogenation.

Engineering and Performance of Ruthenium Complexes Immobilized on Mesoporous Siliceous Materials as Racemization Catalysts

Dynamic kinetic resolution (DKR) is one of the most attractive routes to enantioselective synthesis, and ruthenium complexes are often applied as racemization catalysts. Two substituted cyclopentadienyl ruthenium complexes were immobilized covalently and non-covalently on mesoporous silica of mesocellular foam (MCF) and Santa Barbara Amorphous (SBA)-15 type functionalized with a 3 carbon spacer and 4-(chloromethyl)-N-amidobenzoate moiety. The catalysts were studied in a model reaction of secondary alcohol racemization. The immobilization decreased catalyst activity, considerably more for SBA-15 than for MCFs, and complete racemization of 1-phenylethanol was achieved within 24 h with the MCF-supported catalyst. The catalyst could be recovered and reused, thus paving the way for further development of the DKR process. The synthesized materials were fully characterized by Fourier-transform infrared spectroscopy analysis, thermogravimetry analysis, inductively cou-pled plasma optical emission spectrometry, and nitrogen adsorption at 77 K.

Modified silicates and carbon nanotubes for immobilization of lipase from Rhizomucor miehei: Effect of support and immobilization technique on the catalytic performance of the immobilized biocatalysts

Lipase from Rhizomucor miehei (RML) was covalently immobilized on different supports, two silica gels and two carbon nanotube samples, using two different strategies. RML was immobilized on 3-carboxypropyl silica gel (RML@Si-COOH) and multi-wall carbon nanotubes containing carboxylic acid functionalities (RML@MCNT-COOH) using a two-step carbodiimide activation/immobilization reaction. Moreover, the enzyme was also immobilized on 3-aminopropyl silica (RML@Si-Glu) and single-wall carbon nanotubes functionalized with 3-APTES and activated with glutaraldehyde (RML@SCNT-Glu). Before and after RML immobilization, the structurel properties of supports were characterized and compared in detail. After immobilization, the expressed activities were 36.9, 90.2, 16.9, and 26.1 % for RML@Si-COOH, RML@Si-Glu, RML@MCNT-COOH, and RML@SCNT-Glu, respectively. The kinetic parameters of free and immobilized RML samples were determined for three substrates, p-nitrophenyl acetate, p-nitrophenyl butyrate and p-nitrophenyl palmitate, and RML@Si-Glu showed higher catalytic efficiency than the other immobilized RML samples. RML@Si-COOH, RML@Si-Glu, RML@MCNT-COOH, and RML@SCNT-Glu exhibited 5.8, 7.6, 4.2 and 4.6 folds longer half-life values than those of the free enzyme at pH 7.5 and 40 °C. Recyclability studies showed that all the immobilized RML biocatalysts retained over 90 % of their initial activities after ten cycles in the hydrolysis of p-nitrophenyl butyrate.