Putting precision and elegance in enzyme immobilisation with bio-orthogonal chemistry

Site-directed immobilization of enzymes on microporous resins depended on transglutaminase-catalyzed bioconjugation

Enzyme immobilization has emerged as a powerful strategy for enhancing enzyme stability. However, traditional methods of random enzyme immobilization often result in reduced catalytic activity due to disruption of the active sites and conformation of the enzyme molecules. Here, we developed a convenient strategy to immobilize enzymes on microporous amino resins through transglutaminase-catalyzed bioconjugation. We utilized L-2-haloacid dehalogenase (L-HADST) as a model enzyme. The target enzyme was specifically anchored to the surface of the resins by fusing the QH-tag (CSAWRHPQFGG) of L-HADST and the free amino groups on the resins catalyzed by microbial transglutaminase (MTG). The covalently immobilized complex, L-HAD@AmR, exhibits significantly enhanced stability and catalytic performance compared to free L-HADST, resulting in a 2.32-fold increase in thermal stability and a degradation rate exceeding 99.9 % for S-(-)-2-chloropropionic acid. Furthermore, L-HAD@AmR retained approximately 81 % of its initial degradation rate after six consecutive cycles, which is markedly superior to the performance of the randomly immobilized complex via physical adsorption (L-HAD&AmR), which retained only 22 % of its initial degradation rate after the third cycle. These results suggest that MTG-catalyzed bioconjugation represents an alternative method for the ordered immobilization of enzymes on the solid supports, with potential applications in biocatalysis and bioremediation.

Advances and Challenges in the Development of Immobilized Enzymes for Batch and Flow Biocatalyzed Processes

The development of immobilized enzymes both for batch and continuous flow biocatalytic processes has gained significant traction in recent years, driven by the need for cost-effective and sustainable production methods in the fine chemicals and pharmaceutical industries. Enzyme immobilization not only enables the recycling of biocatalysts but also streamlines downstream processing, significantly reducing the cost and environmental impact of biotransformations. This review explores recent advancements in enzyme immobilization techniques, covering both carrier-free methods, entrapment strategies and support-based approaches. At this regard, the selection of suitable materials for enzyme immobilization is examined, highlighting the advantages and challenges associated with inorganic, natural, and synthetic organic carriers. Novel opportunities coming from innovative binding strategies, such as genetic fusion technologies, for the preparation of heterogeneous biocatalysts with enhanced activity and stability will be discussed as well. This review underscores the need for ongoing research to address current limitations and optimize immobilization strategies for industrial applications.

Application of magnetic aldehyde-functionalized ionic liquids for immobilization of acetylcholinesterase

This study presents a simple and efficient approach for enzyme immobilization using magnetic aldehyde-functionalized ionic liquids, with acetylcholinesterase (AChE) as a model enzyme. We synthesized a new magnetic particle, Fe3O4@SiO2@[ImBa][Cl], by modifying silica-coated Fe3O4 with the ionic liquid 4-(imidazol-1-yl)benzaldehyde hydrochloride ([ImBa][Cl]), whose structure was characterized by SEM, TEM, FT-IR, EDS, TGA and VSM. Immobilization of AChE occurred through both physical adsorption and covalent bonding, driven by electrostatic interaction between cations of the ionic liquid and AChE, as well as Schiff base reaction between the aldehyde groups and protein amines. We identified the optimal immobilization conditions including solution pH (7), AChE concentration (0.8 mg/mL) and incubation time (90 min), under which the immobilization yield reached 16.38 μg/mg. Compared to free AChE, the immobilized AChE exhibited superior substrate affinity and catalytic activity based on kinetic study, also outperforming traditional covalent immobilization methods that utilized glutaraldehyde as cross-linker. Furthermore, the immobilized AChE demonstrated excellent reusability, as well as enhanced storage and thermal stability compared to free AChE. Additionally, it was employed for evaluation of drug inhibitory activity, which could be used for relevant drug discovery. This method indicates that magnetic aldehyde-functionalized ionic liquids are simple and efficient carriers for immobilization of enzymes.

Urease-coupled systems and materials: design strategies, scope and applications

Synthetic systems have co-opted urease, a crucial enzyme serving many biological functions, to recapitulate complex biological features. Therefore, the urease-urea feedback reaction network (FCRN) is reciprocated with soft materials to induce various animate-like features, including self-regulation, error correction, and decision-making capabilities, that are processed through a variety of non-linear functions. Although free-urease-based homogeneous systems are capable of adhering to many non-linear characteristics, they lack the ability to showcase the diffusion-controlled spatiotemporal phenomena. Therefore, it demands urease immobilization, whereby a compartmentalized reaction hub can facilitate the interplay of FCRN with reaction diffusion to regulate the system's operation, allowing various non-linear responses and spatiotemporal self-organization. Indeed, the beneficial framework of urease-based commercial systems in modern technology necessitates the accessibility, reusability, and long-term stability of urease. Consequently, several techniques for urease immobilization merit attention. This review highlights the diverse covalent and non-covalent approaches for urease immobilization on different substrates and illustrates several chemical reactions and non-covalent interactions as tools for creating targeted systems and soft materials to realize many on-demand functions. We also emphasize how the advancement of systems chemistry has propelled research in soft materials to comprehend system-level applications by demonstrating several emerging non-linear functions with potent applications in many directions, including sensing, soft robotics, regulation of material properties and many more.

Sustainable bioactive hydrogels for organic contaminant elimination in wastewater

Immobilized enzyme bioremediation is a promising technique for eliminating pollutants to alleviate water scarcity pressure but is severely hindered by poor enzymatic activity and stability. An effective charge-assisted H-bonding approach is developed to achieve high laccase loading and enzymatic activity on bio(cellulose)-based hydrogels. Notably, this strategy can be readily extended to lipase and catalase. The bio-based hydrogels are synthesized by grafting deoxyribonucleic acid onto the cellulose backbone through a one-step structural regulation, achieving high mechanical strength, enzyme loading and contaminant capture for degradation. The biocompatible laccase-immobilized hydrogels exhibit significant removal and degradation performance for diverse organic micropollutants, including parent and substituted polycyclic aromatic hydrocarbons, per- and polyfluoroalkyl substances, antibiotics and organic dyes. Further testing focused on parent and substituted polycyclic aromatic hydrocarbons shows minimal influence of various co-existing interfering substances on performance of the laccase-immobilized bioactive hydrogel, with its contaminant removal and degradation efficiency in authentic wastewater being 93.0- and 64.3-fold that of commercial free laccase, respectively. This work provides an effective strategy for sustainable bioremediation of wastewater and other pollutant streams, while simultaneously enabling the development of innovative enzyme catalysts.

Turning the band alignment of carbon dots for visible-light-driven enzymatic asymmetric reduction of aromatic ketone

Keto reductases are crucial NAD(P)H-dependent enzymes used for the enantioselective synthesis of alcohols from prochiral ketones. Typically, the NADPH cofactor is regenerated through a second enzyme and/or substrate. However, photocatalytic cofactor regeneration using water as a sacrificial electron and hydrogen donor presents a promising alternative, albeit a challenging one. Herein we fabricated several nitrogen-doped carbon dots (CDs) with visible light absorption properties, good water solubility and biocompatibility for photocatalytic regeneration of NADPH. The CD with a smaller size and suitable redox potential gave the highest NADPH yield (55.7 %). Based on this, NADPH-dependent aldo-keto reductase crosslinked aggregates (AKR-CLEs) were initially applied as a stable biocatalyst to reduce the prochiral ketone. (S)-1-(2-Chlorophenyl) ethanol, an intermediate for LPA1R antagonists, was obtained in 65.3 % yield and 99.99 % enantiomeric excess (ee) under visible light irradiation. The isotope tracer experiment confirmed that water is the hydrogen donor in this light-driven, photo-enzymatic asymmetric hydrogenation system. This method is useful for the sustainable synthesis of chiral alcohols. Moreover, the general principle of utilizing water as the sacrificial hydrogen and electron donor holds potential for application in other redox cofactor regeneration systems.

Nanozyme-based wearable biosensors for application in healthcare

Recent years have witnessed tremendous advances in wearable sensors, which play an essential role in personalized healthcare for their ability for real-time sensing and detection of human health information. Nanozymes, capable of mimicking the functions of natural enzymes and addressing their limitations, possess unique advantages such as structural stability, low cost, and ease of mass production, making them particularly beneficial for constructing recognition units in wearable biosensors. In this review, we aim to delineate the latest advancements in nanozymes for the development of wearable biosensors, focusing on key developments in nanozyme immobilization strategies, detection technologies, and biomedical applications. The review also highlights the current challenges and future perspectives. Ultimately, it aims to provide insights for future research endeavors in this rapidly evolving area.

A new method to immobilize urease in silk fibroin membrane by unidirectional nanopore dehydration

The immobilization of free enzymes is crucial for enhancing their stability in different environments, enabling reusability, and expanding their applications. However, the development of a straightforward immobilization method that offers stability, high efficiency, biocompatibility, and modifiability remains a significant challenge. Silk fibroin (SF) is a good carrier for immobilized enzymes and drugs. Here, we employed urease as a model enzyme and utilized our developed technology called unidirectional nanopore dehydration (UND) to efficiently dehydrate a regenerated SF solution containing urease in a single step, resulting in the preparation of a highly functionalized SF membrane immobilizing urease (UI-SFM). The preparation process of UI-SFM is based on an all-water system, which is mild, green and able to efficiently and stably immobilize urease in the membranes, maintaining 92.7% and 82.8% relative enzyme activity after 30 days of storage in dry and hydrated states, respectively. Additionally, we performed additional post-treatments, including stretching and cross-linking with polyethylene glycol diglycidyl ether (PEGDE), to obtain two more robust immobilized urease membranes (UI-SFMs and UI-SFMc). The thermal and storage stability of these two membranes were significantly improved, and the recovery ratio of enzyme activity reached more than 90%. After 10 repetitions of the enzymatic reaction, the activity recovery of UI-SFMs and UI-SFMc remained at 92% and 88%, respectively. The results suggest that both UND-based and post-treatment-developed membranes exhibit excellent urease immobilization capabilities. Furthermore, the enzyme immobilization method offers a straightforward and versatile approach for efficient and stable enzyme immobilization, while its flexible modifiability caters to diverse application requirements.

Combining Protein Phase Separation and Bio-orthogonal Linking to Coimmobilize Enzymes for Cascade Biocatalysis

The designed and ordered co-immobilization of multiple enzymes for vectorial biocatalysis is challenging. Here, a combination of protein phase separation and bioorthogonal linking is used to generate a zeolitic imidazole framework (ZIF-8) containing co-immobilized enzymes. Zn2+ ions induce the clustering of minimal protein modules, such as 6-His tag, proline-rich motif (PRM) and SRC homology 3 (SH3) domains, and allow for phase separation of the coupled aldoketoreductase (AKR) and alcohol dehydrogenase (ADH) at low concentrations. This is achieved by fusing SpyCatcher and PRM-SH3-6His peptide fragments to the C and N termini of AKR, respectively, and the SpyTag to ADH. Addition of 2-methylimidazole results in droplet formation and enables in situ spatial embedding the recombinant AKR and ADH to generate the cascade biocalysis system encapsulated in ZIF-8 (AAE@ZIF). In synthesizing (S)-1-(2-chlorophenyl) ethanol, ater 6 cycles, the yield can still reach 91%, with 99.99% enantiomeric excess (ee) value for each cycle. However, the yield could only reach 72.9% when traditionally encapsulated AKR and ADH in ZIF-8 are used. Thus, this work demonstrates that a combination of protein phase separation and bio-orthogonal linking enables the in situ creation of a stable and spatially organized bi-enzyme system with enhanced channeling effects in ZIF-8.

A Universal Approach for High-Yield Synthesis of Single-Crystalline Ordered Macro-Microporous Metal-Organic Frameworks

Despite the excellent properties of single-crystalline ordered macro-microporous MOFs (SOM-MOFs) compared to conventional MOFs, their further development has been hindered by the lack of versatile and high-yielding preparation protocols. This study introduces an innovative universal fabrication method that can easily solve the two major challenges of precursor stabilization and crystallization modulation, enabling the efficient synthesis of various SOM-MOFs with high yields. Notably, our approach has successfully yielded SOM-MIL-88A, a novel MOF showcasing exceptional stability in both water and acidic solutions, a remarkable achievement unprecedented in prior SOM-MOF research. SOM-MIL-88A has demonstrated exponentially improved performance over conventional MIL-88A in adsorption, catalysis, immobilized enzymes, and composite biosensing. Furthermore, our versatile protocol has been successfully applied to synthesize SOM-HKUST-1 and SOM-ZIF-8, resulting in significantly improved yields (increase by about 10-fold and 2-fold, respectively, compared to the previously reported protocol). This groundbreaking achievement marks a pivotal advancement in the preparation of diverse SOM-MOFs with tailored properties, presenting exciting prospects for future research on MOFs.

Bioorthogonal chemistry-based prodrug strategies for enhanced biosafety in tumor treatments: current progress and challenges

Cancer is a significant global health challenge, and while chemotherapy remains a widely used treatment, its non-specific toxicity and broad distribution can lead to systemic side effects and limit its effectiveness against tumors. Therefore, the development of safer chemotherapy alternatives is crucial. Prodrugs hold great promise, as they remain inactive until they reach the cancer site, where they are selectively activated by enzymes or specific factors, thereby reducing side effects and improving targeting. However, subtle differences in the microenvironments between tumors and normal tissue may still result in unintended cytotoxicity. Bioorthogonal reactions, known for their selectivity and precision without interfering with natural biochemical processes, are gaining attention. When combined with prodrug strategies, these reactions offer the potential to create highly effective chemotherapy drugs. This review examines the safety and efficacy of prodrug strategies utilizing various bioorthogonal reactions in cancer treatment.

Waste Valorization in a Sustainable Bio-Based Economy: The Road to Carbon Neutrality

The development of sustainable chemistry underlying the quest to minimize and/or valorize waste in the carbon-neutral manufacture of chemicals is followed over the last four to five decades. Both chemo- and biocatalysis have played an indispensable role in this odyssey. in particular developments in protein engineering, metagenomics and bioinformatics over the preceding three decades have played a crucial supporting role in facilitating the widespread application of both whole cell and cell-free biocatalysis. The pressing need, driven by climate change mitigation, for a drastic reduction in greenhouse gas (GHG) emissions, has precipitated an energy transition based on decarbonization of energy and defossilization of organic chemicals production. The latter involves waste biomass and/or waste CO2 as the feedstock and green electricity generated using solar, wind, hydroelectric or nuclear energy. The use of waste polysaccharides as feedstocks will underpin a renaissance in carbohydrate chemistry with pentoses and hexoses as base chemicals and bio-based solvents and polymers as environmentally friendly downstream products. The widespread availability of inexpensive electricity and solar energy has led to increasing attention for electro(bio)catalysis and photo(bio)catalysis which in turn is leading to myriad innovations in these fields.

Advances in aldo-keto reductases immobilization for biocatalytic synthesis of chiral alcohols

Chiral alcohols are essential building blocks of numerous pharmaceuticals and fine chemicals. Aldo-keto reductases (AKRs) constitute a superfamily of oxidoreductases that catalyze the reduction of aldehydes and ketones to their corresponding alcohols using NAD(P)H as a coenzyme. Knowledge about the crucial roles of AKRs immobilization in the biocatalytic synthesis of chiral alcohols is expanding. Herein, we reviewed the characteristics of various AKRs immobilization approaches, the applications of different immobilization materials, and the prospects of continuous flow bioreactor construction by employing these immobilized biocatalysts for synthesizing chiral alcohols. Finally, the opportunities and ongoing challenges for AKR immobilization are discussed and the outlook for this emerging area is analyzed.

When nanozymes meet enzyme: Unlocking the dual-activity potential of integrated biocomposites

Integrating enzymes and nanozymes in various applications is a topic of significant interest. The researchers have explored the encapsulation of enzymes using diverse nanostructures to create nanomaterial-enzyme hybrids. These nanomaterials introduce unique properties that contribute to the additional activity along with the stabilization of enzymes in immobilized form, enabling a cascade of second-order reactions. This review centers on dual-activity nanozymes, providing insights into their applications in biosensors and biocatalysis. These applications leverage the enhanced catalytic activity and stability offered by dual-activity nanozymes. These nanozymes find promising applications in fields like bioremediation, offering eco-friendly solutions for mitigating environmental pollution while showing potential in medical diagnostics. The review delves into various techniques for creating enzyme-nanozyme hybrid catalysts, including adsorption, encapsulation, and incorporation methods. The review also addresses the challenges that must be overcome, such as overlapping catalytic surfaces and disparities in reaction rates in multi-enzyme cascade reactions. It concludes by presenting strategies to tackle these issues and offers insights into the field's promising future, suggesting that machine learning may drive further advancements in enzyme-nanozyme integration. This comprehensive exploration illuminates the present and charts a promising course for future innovations in the seamless integration of enzymes and nanozymes, heralding a new era of catalytic possibilities.

Precision Engineering of the Co-immobilization of Enzymes for Cascade Biocatalysis

The design and orderly layered co-immobilization of multiple enzymes on resin particles remain challenging. In this study, the SpyTag/SpyCatcher binding pair was fused to the N-terminus of an alcohol dehydrogenase (ADH) and an aldo-keto reductase (AKR), respectively. A non-canonical amino acid (ncAA), p-azido-L-phenylalanine (p-AzF), as the anchor for covalent bonding enzymes, was genetically inserted into preselected sites in the AKR and ADH. Employing the two bioorthogonal counterparts of SpyTag/SpyCatcher and azide-alkyne cycloaddition for the immobilization of AKR and ADH enabled sequential dual-enzyme coating on porous microspheres. The ordered dual-enzyme reactor was subsequently used to synthesize (S)-1-(2-chlorophenyl)ethanol asymmetrically from the corresponding prochiral ketone, enabling the in situ regeneration of NADPH. The reactor exhibited a high catalytic conversion of 74 % and good reproducibility, retaining 80 % of its initial activity after six cycles. The product had 99.9 % ee, which that was maintained in each cycle. Additionally, the double-layer immobilization method significantly increased the enzyme loading capacity, which was approximately 1.7 times greater than that of traditional single-layer immobilization. More importantly, it simultaneously enabled both the purification and immobilization of multiple enzymes on carriers, thus providing a convenient approach to facilitate cascade biocatalysis.

Bioremediation of Hazardous Pollutants Using Enzyme-Immobilized Reactors

Bioremediation uses the degradation abilities of microorganisms and other organisms to remove harmful pollutants that pollute the natural environment, helping return it to a natural state that is free of harmful substances. Organism-derived enzymes can degrade and eliminate a variety of pollutants and transform them into non-toxic forms; as such, they are expected to be used in bioremediation. However, since enzymes are proteins, the low operational stability and catalytic efficiency of free enzyme-based degradation systems need improvement. Enzyme immobilization methods are often used to overcome these challenges. Several enzyme immobilization methods have been applied to improve operational stability and reduce remediation costs. Herein, we review recent advancements in immobilized enzymes for bioremediation and summarize the methods for preparing immobilized enzymes for use as catalysts and in pollutant degradation systems. Additionally, the advantages, limitations, and future perspectives of immobilized enzymes in bioremediation are discussed.

Adsorption features of reduced aminated supports modified with glutaraldehyde: Understanding the heterofunctional features of these supports

Immobilization of enzymes on aminated supports using the glutaraldehyde chemistry may involve three different interactions, cationic, hydrophobic, and covalent interactions. To try to understand the impact this heterofunctionality, we study the physical adsorption of the beta-galactosidase from Aspergillus niger, on aminated supports (MANAE) and aminated supports with one (MANAE-GLU) or two molecules of glutaraldehyde (MANAE-GLU-GLU). To eliminate the chemical reactivity of the glutaraldehyde, the supports were reduced using sodium borohydride. After enzyme adsorption, the release of the enzyme from the supports using different NaCl concentrations, Triton X100, ionic detergents (SDS and CTAB), or different temperatures (4 °C to 55 °C) was studied. Using MANAE support, at 0.3 M NaCl almost all the immobilized enzyme was released. Using MANAE-GLU, 0.3 M, and 0.6 M NaCl similar results were obtained. However, incubation at 1 M or 2 M NaCl, many enzyme molecules were not released from the support. For the MANAE-GLU-GLU support, none of the tested concentrations of NaCl was sufficient to release all enzyme bound to the support. Only using high temperatures, 0.6 M NaCl, and 1 % CTAB or SDS, could the totality of the proteins be released from the support. The results shown in this paper confirm the heterofunctional character of aminated supports modified with glutaraldehyde.

Near-infrared light-driven asymmetric photolytic reduction of ketone using inorganic-enzyme hybrid biocatalyst

Effective photolytic regeneration of the NAD(P)H cofactor in enzymatic reductions is an important and elusive goal in biocatalysis. It can, in principle, be achieved using a near-infrared light (NIR) driven artificial photosynthesis system employing H2O as the sacrificial reductant. To this end we utilized TiO2/reduced graphene quantum dots (r-GQDs), combined with a novel rhodium electron mediator, to continuously supply NADPH in situ for aldo-keto reductase (AKR) mediated asymmetric reductions under NIR irradiation. This upconversion system, in which the Ti-O-C bonds formed between r-GQDs and TiO2 enabled efficient interfacial charge transfer, was able to regenerate NADPH efficiently in 64 % yield in 105 min. Based on this, the pharmaceutical intermediate (R)-1-(3,5-bis(trifluoromethyl)phenyl)ethan-1-ol was obtained, in 84 % yield and 99.98 % ee, by reduction of the corresponding ketone. The photo-enzymatic system is recyclable with a polymeric electron mediator, which maintained 66 % of its original catalytic efficiency and excellent enantioselectivity (99.9 % ee) after 6 cycles.

Biomaterials containing extracellular matrix molecules as biomimetic next-generation vascular grafts

The performance of synthetic biomaterial vascular grafts for the bypass of stenotic and dysfunctional blood vessels remains an intractable challenge in small-diameter applications. The functionalization of biomaterials with extracellular matrix (ECM) molecules is a promising approach because these molecules can regulate multiple biological processes in vascular tissues. In this review, we critically examine emerging approaches to ECM-containing vascular graft biomaterials and explore opportunities for future research and development toward clinical use.

Encapsulation of lipase in zeolitic imidazolate framework-8 induced by polyethyleneimine to form a honeycomb structure with enhanced activity

Embedding an enzyme in the metal-organic frameworks (MOFs) gives good protection to the fragile enzyme. However, this may also restrain the enzyme activity because of the decreased substrate accessibility. Encapsulation of lipase AK from Pseudomonas fluorescens for preparing the enzyme-MOF composite (AK@ZIF-8-PEI) was performed through a new strategy based on polyethyleneimine and enzyme induced in-situ growth of zeolitic imidazolate framework-8 (ZIF-8). Characterizations indicate that AK@ZIF-8-PEI has a honeycomb structure and the hierarchical porosity formed during the preparation, which provides adequate mass transfer channels for catalytic applications. Activity evaluation shows that specific activity of AK@ZIF-8-PEI is 8-fold than the commercial lipase powder. AK@ZIF-8-PEI is demonstrated as an efficient catalyst in kinetic resolution of α-naphthol enantiomers through enantioselective transesterification. Within 12 h, the conversion and substrate enantiomeric excess (ees) reaches 49.8 % and 96.4 %, achieving an improved resolution than previous researches.

Nanomaterial surface modification toolkit: Principles, components, recipes, and applications

Surface-functionalized nanostructures are at the forefront of biotechnology, providing new opportunities for biosensors, drug delivery, therapy, and bioimaging applications. The modification of nanostructures significantly impacts the performance and success of various applications by enabling selective and precise targeting. This review elucidates widely practiced surface modification strategies, including click chemistry, cross-coupling, silanization, aldehyde linkers, active ester chemistry, maleimide chemistry, epoxy linkers, and other protein and DNA-based methodologies. We also delve into the application-focused landscape of the nano-bio interface, emphasizing four key domains: therapeutics, biosensing, environmental monitoring, and point-of-care technologies, by highlighting prominent studies. The insights presented herein pave the way for further innovations at the intersection of nanotechnology and biotechnology, providing a useful handbook for beginners and professionals. The review draws on various sources, including the latest research articles (2018-2023), to provide a comprehensive overview of the field.

Atrazine Degradation Using Immobilized Triazine Hydrolase from Arthrobacter aurescens TC1 in Mesoporous Silica Nanomaterials

Triazine hydrolase fromArthrobacter aurescens TC1 (TrzN) was successfully immobilized on mesoporous silica nanomaterials (MSNs) for the first time. For both nonfunctionalized MSNs and MSNs functionalized with Zn(II), three pore sizes were evaluated for their ability to immobilize wild-type TrzN: Mobile composition of matter no. 41 (small, 3 nm pores), mesoporous silica nanoparticle material with 10 nm pore diameter (MSN-10) (medium, 6-12 nm pores), and pore-expanded MSN-10 (large, 15-30 nm pores). Of these six TrzN:MSN biomaterials, it was shown that TrzN:MSN-10 was the most active (3.8 ± 0.4 × 10-5 U/mg) toward the hydrolysis of a 50 μM atrazine solution at 25 °C. The TrzN:MSN-10 biomaterial was then coated in chitosan (TrzN:MSN-10:Chit) as chitosan has been shown to increase stability in extreme conditions such as low/high pH, heat shock, and the presence of organic solvents. TrzN:MSN-10:Chit was shown to be a superior TrzN biomaterial to TrzN:MSN-10 as it exhibited higher activity under all storage conditions, in the presence of 20% MeOH, at low and high pH values, and at elevated temperatures up to 80 °C. Finally, the TrzN:MSN-10:Chit biomaterial was shown to be fully active in river water, which establishes it as a functional biomaterial under actual field conditions. A combination of these data indicate that the TrzN:MSN-10:Chit biomaterial exhibited the best overall catalytic profile making it a promising biocatalyst for the bioremediation of atrazine.

Precise surface functionalization of PLGA particles for human T cell modulation

The biofunctionalization of synthetic materials has extensive utility for biomedical applications, but approaches to bioconjugation typically show insufficient efficiency and controllability. We recently developed an approach by building synthetic DNA scaffolds on biomaterial surfaces that enables the precise control of cargo density and ratio, thus improving the assembly and organization of functional cargos. We used this approach to show that the modulation and phenotypic adaptation of immune cells can be regulated using our precisely functionalized biomaterials. Here, we describe the three key procedures, including the fabrication of polymeric particles engrafted with short DNA scaffolds, the attachment of functional cargos with complementary DNA strands, and the surface assembly control and quantification. We also explain the critical checkpoints needed to ensure the overall quality and expected characteristics of the biological product. We provide additional experimental design considerations for modifying the approach by varying the material composition, size or cargo types. As an example, we cover the use of the protocol for human primary T cell activation and for the identification of parameters that affect ex vivo T cell manufacturing. The protocol requires users with diverse expertise ranging from synthetic materials to bioconjugation chemistry to immunology. The fabrication procedures and validation assays to design high-fidelity DNA-scaffolded biomaterials typically require 8 d.

An enzyme-centric approach for constructing an amperometric l-malate biosensor with a long and programmable linear range

l-Malate is a key flavor enhancer and acidulant in the food and beverage industry, particularly winemaking. Enzyme-based amperometric biosensors offer convenience for monitoring its concentration. However, only a small number of off-the-shelf malate-oxidizing enzymes have been used in previous devices. These typically have linear ranges poorly suited for the l-malate concentrations found in fruit processing and winemaking, making it necessary to use precisely diluted samples. Here, we describe a pipeline of database-mining, gene synthesis, recombinant expression, and spectrophotometric assays to characterize previously untested enzymes for their suitability in biosensors. The pipeline yielded a bespoke biocatalyst-the Ascaris suum malic enzyme carrying mutation R181Q [AsME(R181Q)]. Our first prototype with AsME(R181Q) had an ultra-wide linear range of 50-200 mM l-malate, corresponding to concentrations found in undiluted fruit juices (including grape). Changing the dication from Mg2+ to Mn2+ increased sensitivity five-fold and adding citrate (100 mM) increased it another six-fold, albeit decreasing the linear range to 1-10 mM. To our knowledge, this is the first time an l-malate biosensor with a tuneable combination of sensitivity and linear range has been described. The sensor response was also tested in the presence of various molecules abundant in juices and wines, with ascorbate shown to be a potent interferent. Interference was mitigated by the addition of ascorbate oxidase, allowing for differential measurements on an undiluted, untreated wine sample that corresponded well with commercial l-malate testing kits. Overall, this work demonstrates the power of an enzyme-centric approach for designing electrochemical biosensors with improved operational parameters and novel functionality.

Performance of a Flow-Through Enzyme Reactor Prepared from a Silica Monolith and an α-Poly(D-Lysine)-Enzyme Conjugate

Horseradish peroxidase (HRP) is covalently bound in aqueous solution to polycationic α-poly(D-lysine) chains of ≈1000 repeating units length, PDL, via a bis-aryl hydrazone bond (BAH). Under the experimental conditions used, about 15 HRP molecules are bound along the PDL chain. The purified PDL-BAH-HRP conjugate is very stable when stored at micromolar HRP concentration in a pH 7.2 phosphate buffer solution at 4 °C. When a defined volume of such a conjugate solution of desired HRP concentration (i.e., HRP activity) is added to a macro- and mesoporous silica monolith with pore sizes of 20-30 µm as well as below 30 nm, quantitative and stable noncovalent conjugate immobilization is achieved. The HRP-containing monolith can be used as flow-through enzyme reactor for bioanalytical applications at neutral or slightly alkaline pH, as demonstrated for the determination of hydrogen peroxide in diluted honey. The conjugate can be detached from the monolith by simple enzyme reactor washing with an aqueous solution of pH 5.0, enabling reloading with fresh conjugate solution at pH 7.2. Compared to previously investigated polycationic dendronized polymer-enzyme conjugates with approximately the same average polymer chain length, the PDL-BAH-HRP conjugate appears to be equally suitable for HRP immobilization on silica surfaces.

Enhancing Enzyme Activity Using Hydrophilic Hollow Layered Double Hydroxides as Encapsulation Carriers

Enzyme immobilization enables the fabrication of flexible and powerful biocatalytic systems that can meet the needs of green and efficient development in various fields. However, restricted electron and mass transfer during enzymatic reactions and disruption of the enzyme structure during encapsulation limit the wide application of the immobilized enzyme systems. Herein, we report an encapsulation strategy based on hollow-shell-layered double hydroxides (LDHs; ZnCo-LDH) for green and nondestructive enzyme immobilization. Benefiting from the protective and enzyme-friendly microenvironment provided by the hydrophilic hollow structure of ZnCo-LDH, the encapsulated enzyme maintains a nearly natural enzyme biostructure and enhanced stability. Notably, mesoporous ZnCo-LDH with excellent electrical properties considerably facilitates electron and mass transport during enzymatic reactions, exhibiting 5.56 times the catalytic efficiency of free enzymes or traditional enzyme encapsulation systems. The current study broadens the family of encapsulated carriers and alleviates the trade-off between enzyme stability and catalytic activity in the encapsulated state, presenting a promising avenue for the industrial application of the enzyme.

Grafting of proteins onto polymeric surfaces: A synthesis and characterization challenge

This review aims at answering the following question: how can a researcher be sure to succeed in grafting a protein onto a polymer surface? Even if protein immobilization on solid supports has been used industrially for a long time, hence enabling natural enzymes to serve as a powerful tool, emergence of new supports such as polymeric surfaces for the development of so-called intelligent materials requires new approaches. In this review, we introduce the challenges in grafting protein on synthetic polymers, mainly because compared to hard surfaces, polymers may be sensitive to various aqueous media, depending on the pH or reductive molecules, or may exhibit state transitions with temperature. Then, the specificity of grafting on synthetic polymers due to difference of chemical functions availability or difference of physical properties are summarized. We present next the various available routes to covalently bond the protein onto the polymeric substrates considering the functional groups coming from the monomers used during polymerization reaction or post-modification of the surfaces. We also focus our review on a major concern of grafting protein, which is avoiding the potential loss of function of the immobilized protein. Meanwhile, this review considers the different methods of characterization used to determine the grafting efficiency but also the behavior of enzymes once grafted. We finally dedicate the last part of this review to industrial application and future prospective, considering the sustainable processes based on green chemistry.

Immobilization and property of penicillin G acylase on amino functionalized magnetic Ni0.3Mg0.4Zn0.3Fe2O4 nanoparticles prepared via the rapid combustion process

Penicillin G acylase plays an important role in the biocatalytic process of semi-synthetic penicillin. In order to overcome the disadvantages of free enzymes and improve the catalytic performance of enzymes, it is a new method to immobilize enzymes on carrier materials. And magnetic materials have the characteristics of easy separation. In the present study, the Magnetic Ni0.3Mg0.4Zn0.3Fe2O4 nanoparticles were successfully prepared by a rapid-combustion method and calcined at 400°C for 2 h. The surface of the nanoparticles was modified with sodium silicate hydrate, and the PGA was covalently bound to the carrier particles through the cross-linking of glutaraldehyde. The results showed that the activity of immobilized PGA reached 7121.00 U/g. The optimum pH for immobilized PGA was 8 and the optimum temperature was 45°C, the immobilized PGA exhibited higher stability against changes in pH and temperature. The Michaelis–Menten constant (Km) values of the free and immobilized PGA were 0.00387 and 0.0101 mol/L and the maximum rate (Vmax) values were 0.387 and 0.129 μmol/min. Besides, the immobilized PGA revealed excellent cycling performance. The immobilization strategy presented PGA had the advantages of reuse, good stability, cost saving and had considerable practical significance for the commercial application of PGA.