Agarose and Its Derivatives as Supports for Enzyme Immobilization

Rational design of agarose/dextran composite microspheres with tunable core-shell microstructures for chromatographic application

A new type of core-shell microsphere was prepared by a pre-crosslinking method, consisting of cross-linked agarose microspheres as the core and agarose-dextran as the shell. After optimizing the preparation process, the microspheres with a uniform particle size were obtained and characterized using cryo-scanning electron microscopy to determine their surface and cross-sectional morphology. Results from flow rate-pressure and chromatographic performance tests showed that the core-shell agarose microspheres were supported by the core microspheres and composed of composite polysaccharides, forming an interpenetrating polymer network structure as a hard shell. The core-shell agarose microspheres showed a 300.5 % increase in linear flow rate compared to composite polysaccharide microspheres prepared from shell materials and a 141.5 % increase compared to 6 % agarose microspheres. Additionally, the large pore structure of the shell combined with the fine pore structure of the core improved the material separation efficiency in the range of 0.1-2000 kDa. These findings suggest that core-shell natural polysaccharide microspheres have great potential as a separation chromatographic medium.

Chimeric AQP4-based immunosorbent for highly-specific removal of AQP4-IgG from blood

Anti-aquaporin-4 autoantibodies (AQP4-IgG) are implicated in the pathogenesis of neuromyelitis optica spectrum disorders (NMOSD), and their removal from the blood circulation is considered to be an effective method for acute treatment. An ideal extracorporeal AQP4-IgG removal system should have high specificity, which means that it can selectively remove AQP4-IgG without affecting normal immunoglobulins. However, the conventional tryptophan immobilized column lacks sufficient specificity and cannot achieve this goal. In this study, we successfully prepared a fusion protein chimeric AQP4, which consists of the complete antigenic epitopes of human AQP4 and the constant region of scaffold protein DARPin. Chimeric AQP4 was expressed and purified from Escherichia coli, and then immobilized on agarose gel as a ligand for selective capture of AQP4-IgG immunosorbent. The prepared immunosorbent had a theoretical maximum adsorption capacity of 20.48 mg/g gel estimated by Langmuir isotherm. In vitro plasma perfusion tests demonstrated that the chimeric AQP4 coupled adsorbent had remarkable adsorption performance, and could eliminate more than 85 % of AQP4-IgG under the gel-to-plasma ratio of 1:50. Moreover, it exhibited high specificity because other human plasma proteins were not adsorbed in the dynamic adsorption experiment. These results suggest that the chimeric AQP4 coupled immunosorbent can provide a new approach for specific immunoadsorption (IA) treatment of NMOSD.

Novel 3-D macrophage spheroid model reveals reciprocal regulation of immunomechanical stress and mechano-immunological response

Purpose

In many diseases, an overabundance of macrophages contributes to adverse outcomes. While numerous studies have compared macrophage phenotype after mechanical stimulation or with varying local stiffness, it is unclear if and how macrophages themselves contribute to mechanical forces in their microenvironment.

Methods

Raw 264.7 murine macrophages were embedded in a confining agarose gel, where they proliferated to form spheroids over time. Gels were synthesized at various concentrations to tune the stiffness and treated with various growth supplements to promote macrophage polarization. The spheroids were then analyzed by immunofluorescent staining and qPCR for markers of proliferation, mechanosensory channels, and polarization. Finally, spheroid geometries were used to computationally model the strain generated in the agarose by macrophage spheroid growth.

Results

Macrophages form spheroids and generate growth-induced mechanical forces (i.e., solid stress) within confining agarose gels, which can be maintained for at least 16 days in culture. Increasing agarose concentration restricts spheroid expansion, promotes discoid geometries, limits gel deformation, and induces an increase in iNOS expression. LPS stimulation increases spheroid growth, though this effect is reversed with the addition of IFN-γ. Ki67 expression decreases with increasing agarose concentration, in line with the growth measurements.

Conclusions

Macrophages alone both respond to and generate solid stress. Understanding how macrophage generation of growth-induced solid stress responds to different environmental conditions will help to inform treatment strategies for the plethora of diseases that involve macrophage accumulation.

A systematic study on the characteristics and applications of laccases produced by fungi: insights on their potential for biotechnologies

Laccases are polyphenol oxidase enzymes and form the enzyme complex known for their role in wood decomposition and lignin degradation. The present study aimed to systematically review the state-of-the-art trends in scientific publications on laccase enzymes of the last 10 years. The main aspects checked included the laccase-producing fungal genera, the conditions of fungal growth and laccase production, the methods of immobilization, and potential applications of laccase. After applying the systematic search method 177 articles were selected to compound the final database. Although various fungi produce laccase, most studies were Trametes and Pleurotus genera. The submerged fermentation (SmF) has been the most used, however, the use of solid-state fermentation (SSF) appeared as a promising technique to produce laccase when using agro-industrial residues as substrates. Studies on laccase immobilization showed the covalent bonding and entrapment methods were the most used, showing greater efficiency of immobilization and a high number of enzyme reuses. The main use of the laccase was in bioremediation, especially in the discoloration of dyes from the textile industry and the degradation of pharmaceutical waste. Implications and consequences of all these findings in biotechnology and environment, as well as the trends and gaps of laccase research were discussed.

Proteases immobilized on nanomaterials for biocatalytic, environmental and biomedical applications: Advantages and drawbacks

Proteases have gained significant scientific and industrial interest due to their unique biocatalytic characteristics and broad-spectrum applications in different industries. The development of robust nanobiocatalytic systems by attaching proteases onto various nanostructured materials as fascinating and novel nanocarriers has demonstrated exceptional biocatalytic performance, substantial stability, and ease of recyclability over multiple reaction cycles under different chemical and physical conditions. Proteases immobilized on nanocarriers may be much more resistant to denaturation caused by extreme temperatures or pH values, detergents, organic solvents, and other protein denaturants than free enzymes. Immobilized proteases may present a lower inhibition. The use of non-porous materials in the immobilization prevents diffusion and steric hindrances during the binding of the substrate to the active sites of enzymes compared to immobilization onto porous materials; when using very large or solid substrates, orientation of the enzyme must always be adequate. The advantages and problems of the immobilization of proteases on nanoparticles are discussed in this review. The continuous and batch reactor operations of nanocarrier-immobilized proteases have been successfully investigated for a variety of applications in the leather, detergent, biomedical, food, and pharmaceutical industries. Information about immobilized proteases on various nanocarriers and nanomaterials has been systematically compiled here. Furthermore, different industrial applications of immobilized proteases have also been highlighted in this review.

Current Biomedical Applications of 3D-Printed Hydrogels

Three-dimensional (3D) printing, also known as additive manufacturing, has revolutionized the production of physical 3D objects by transforming computer-aided design models into layered structures, eliminating the need for traditional molding or machining techniques. In recent years, hydrogels have emerged as an ideal 3D printing feedstock material for the fabrication of hydrated constructs that replicate the extracellular matrix found in endogenous tissues. Hydrogels have seen significant advancements since their first use as contact lenses in the biomedical field. These advancements have led to the development of complex 3D-printed structures that include a wide variety of organic and inorganic materials, cells, and bioactive substances. The most commonly used 3D printing techniques to fabricate hydrogel scaffolds are material extrusion, material jetting, and vat photopolymerization, but novel methods that can enhance the resolution and structural complexity of printed constructs have also emerged. The biomedical applications of hydrogels can be broadly classified into four categories-tissue engineering and regenerative medicine, 3D cell culture and disease modeling, drug screening and toxicity testing, and novel devices and drug delivery systems. Despite the recent advancements in their biomedical applications, a number of challenges still need to be addressed to maximize the use of hydrogels for 3D printing. These challenges include improving resolution and structural complexity, optimizing cell viability and function, improving cost efficiency and accessibility, and addressing ethical and regulatory concerns for clinical translation.

Overcoming Biochemical Limitations of Galactose Oxidase through the Design of a Solid-Supported Self-Sufficient Biocatalyst

Galactose Oxidase (GalOx) has gained significant interest in biocatalysis due to its ability for selective oxidation beyond the natural oxidation of galactose, enabling the production of valuable derivatives. However, the practical application of GalOx has been hindered by the limited availability of active and stable biocatalysts, as well as the inherent biochemical limitations such as oxygen (O2 ) dependency and the need for activation. In this study, we addressed these challenges by immobilizing GalOx into agarose-based and Purolite supports to enhance its activity and stability. Additionally, we identified and quantified the oxygen supply limitation into solid catalysts by intraparticle oxygen sensing showing a trade-off between the amount of protein loaded onto the solid support and the catalytic effectiveness of the immobilized enzyme. Furthermore, we coimmobilized a heme-containing protein along with the enzyme to function as an activator. To evaluate the practical application of the immobilized GalOx, we conducted the oxidation of galactose in an instrumented aerated reactor. The results showcased the efficient performance of the immobilized enzyme in the 8 h reaction cycle. Notably, the GalOx immobilized into dextran sulfate-activated agarose exhibited improved stability, overcoming the need for a soluble activator supply, and demonstrated exceptional performance in galactose oxidation. These findings offer promising prospects for the utilization of GalOx in technical biocatalytic applications.

Biomaterials / bioinks and extrusion bioprinting

Bioinks are formulations of biomaterials and living cells, sometimes with growth factors or other biomolecules, while extrusion bioprinting is an emerging technique to apply or deposit these bioinks or biomaterial solutions to create three-dimensional (3D) constructs with architectures and mechanical/biological properties that mimic those of native human tissue or organs. Printed constructs have found wide applications in tissue engineering for repairing or treating tissue/organ injuries, as well as in vitro tissue modelling for testing or validating newly developed therapeutics and vaccines prior to their use in humans. Successful printing of constructs and their subsequent applications rely on the properties of the formulated bioinks, including the rheological, mechanical, and biological properties, as well as the printing process. This article critically reviews the latest developments in bioinks and biomaterial solutions for extrusion bioprinting, focusing on bioink synthesis and characterization, as well as the influence of bioink properties on the printing process. Key issues and challenges are also discussed along with recommendations for future research.

Biopolymers Used for Receptor Immobilization for Nickel-Detection Biosensors in Food

Food is humans' main source of nickel intake, which is responsible for the prevalence of allergic contact dermatitis and other pathological afflictions. While robust, the classical methods for nickel detection-atomic absorption spectrometry and inductively coupled plasma mass spectrometry-are expensive and laborious; in contrast, modern methods that utilize sensors-of which most are electrochemical-have rapid run times, are cost-effective, and are easily assembled. Here, we describe the use of four biopolymers (alginate, agar, chitosan, and carrageenan) for receptor immobilization on biosensors to detect nickel ions and use an optimization approach with three biopolymer concentrations to assay analytical performance profiles. We measured the total performance of screen-printed carbon electrodes immobilized with the biopolymer-sensor combinations using cyclic voltammetry (CV). Voltammetric behavior favored the carrageenan biosensor, based on performance characteristics measured using CV, with sensitivities of 2.68 (for 1% biopolymer concentration) and 2.08 (for 0.5% biopolymer concentration). Our results indicated that among the four biopolymer combinations, carrageenan with urease affixed to screen-printed electrodes was effective at coupling for nickel detection.

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.

Hierarchical covalent organic framework-foam for multi-enzyme tandem catalysis

Covalent organic frameworks (COFs) are ideal host matrices for biomolecule immobilization and biocatalysis due to their high porosity, various functionalities, and structural robustness. However, the porosity of COFs is limited to the micropore dimension, which restricts the immobilization of enzymes with large volumes and obstructs substrate flow during enzyme catalysis. A hierarchical 3D nanostructure possessing micro-, meso-, and macroporosity could be a beneficial host matrix for such enzyme catalysis. In this study, we employed an in situ CO2 gas effervescence technique to induce disordered macropores in the ordered 2D COF nanostructure, synthesizing hierarchical TpAzo COF-foam. The resulting TpAzo foam matrix facilitates the immobilization of multiple enzymes with higher immobilization efficiency (approximately 1.5 to 4-fold) than the COF. The immobilized cellulolytic enzymes, namely β-glucosidase (BGL), cellobiohydrolase (CBH), and endoglucanase (EG), remain active inside the TpAzo foam. The immobilized BGL exhibited activity in organic solvents and stability at room temperature (25 °C). The enzyme-immobilized TpAzo foam exhibited significant activity towards the hydrolysis of p-nitrophenyl-β-d-glucopyranoside (BGL@TpAzo-foam: Km and Vmax = 23.5 ± 3.5 mM and 497.7 ± 28.0 μM min-1) and carboxymethylcellulose (CBH@TpAzo-foam: Km and Vmax = 18.3 ± 4.0 mg mL-1 and 85.2 ± 9.6 μM min-1 and EG@TpAzo-foam: Km and Vmax = 13.2 ± 2.0 mg mL-1 and 102.2 ± 7.1 μM min-1). Subsequently, the multi-enzyme immobilized TpAzo foams were utilized to perform a one-pot tandem conversion from carboxymethylcellulose (CMC) to glucose with high recyclability (10 cycles). This work opens up the possibility of synthesizing enzymes immobilized in TpAzo foam for tandem catalysis.

Advances in Functionalization of Bioresorbable Nanomembranes and Nanoparticles for Their Use in Biomedicine

Bioresorbable nanomembranes (NMs) and nanoparticles (NPs) are powerful polymeric materials playing an important role in biomedicine, as they can effectively reduce infections and inflammatory clinical patient conditions due to their high biocompatibility, ability to physically interact with biomolecules, large surface area, and low toxicity. In this review, the most common bioabsorbable materials such as those belonging to natural polymers and proteins for the manufacture of NMs and NPs are reviewed. In addition to biocompatibility and bioresorption, current methodology on surface functionalization is also revisited and the most recent applications are highlighted. Considering the most recent use in the field of biosensors, tethered lipid bilayers, drug delivery, wound dressing, skin regeneration, targeted chemotherapy and imaging/diagnostics, functionalized NMs and NPs have become one of the main pillars of modern biomedical applications.

An Accessible Method to Improve the Stability and Reusability of Porcine Pancreatic α-Amylase via Immobilization in Gellan-Based Hydrogel Particles Obtained by Ionic Cross-Linking with Mg2+ Ions

Amylase is an enzyme used to hydrolyze starch in order to obtain different products that are mainly used in the food industry. The results reported in this article refer to the immobilization of α-amylase in gellan hydrogel particles ionically cross-linked with Mg2+ ions. The obtained hydrogel particles were characterized physicochemically and morphologically. Their enzymatic activity was tested using starch as a substrate in several hydrolytic cycles. The results showed that the properties of the particles are influenced by the degree of cross-linking and the amount of immobilized α-amylase enzyme. The temperature and pH at which the immobilized enzyme activity is maximum were T = 60 °C and pH = 5.6. The enzymatic activity and affinity of the enzyme to the substrate depend on the particle type, and this decreases for particles with a higher cross-linking degree owing to the slow diffusion of the enzyme molecules inside the polymer's network. By immobilization, α-amylase is protected from environmental factors, and the obtained particles can be quickly recovered from the hydrolysis medium, thus being able to be reused in repeated hydrolytic cycles (at least 11 cycles) without a substantial decrease in enzymatic activity. Moreover, α-amylase immobilized in gellan particles can be reactivated via treatment with a more acidic medium.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

Food-Grade Oleogels: Trends in Analysis, Characterization, and Applicability

Currently, a large number of scientific articles can be found in the research literature in the field focusing on the use of oleogels for food formulation to improve their nutritional properties. The present review focuses on the most representative food-grade oleogels, highlighting current trends in terms of the most suitable methods of analysis and characterization, as well as trends in their application as substitutes for saturated and trans fats in foods. For this purpose, the physicochemical properties, structure, and composition of some oleogelators are primarily discussed, along with the adequacy of oleogel incorporation for use in edible products. Analysis and characterization of oleogels by different methods are important in the formulation of innovative foods, and therefore, this review discusses the most recent published results regarding their microstructure, rheological and textural properties, and oxidative stability. Last but not least, issues related to the sensory properties of oleogel-based foods are discussed, highlighting also the consumer acceptability of some of them.

Carbon Dot-Doped Hydrogel Sensor Array for Multiplexed Colorimetric Detection of Wound Healing

Effective wound care and treatment require a quick and comprehensive assessment of healing status. Here, we develop a carbon dot-doped hydrogel sensor array in polydimethylsiloxane (PDMS) for simultaneous colorimetric detections of five wound biomarkers and/or wound condition indicators (pH, glucose, urea, uric acid, and total protein), leading to the holistic assessment of inflammation and infection. A biogenic carbon dot synthesized using an amino acid and a polymer precursor is doped in an agarose hydrogel matrix for constructing enzymatic sensors (glucose, urea, and uric acid) and dye-based sensors (pH and total protein). The encapsulated enzymes in such a matrix exhibit improved enzyme kinetics and stability compared to those in pure hydrogels. Such a matrix also provides stable colorimetric responses for all five sensors. The sensor array exhibits high accuracy (recovery rates of 91.5-113.1%) and clinically relevant detection ranges for all five wound markers. The sensor array is established for simulated wound fluids and validated with rat wound fluids from perturbed wound models. Distinct color patterns are obtained that can clearly distinguish healing vs nonhealing wounds visually and quantitatively. This hydrogel sensor array shows great potential for on-site wound sensing due to its long-term stability, lightweight, and flexibility.

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.

Minimally invasive electrochemical continuous glucose monitoring sensors: Recent progress and perspective

Diabetes and its complications are seriously threatening the health and well-being of hundreds of millions of people. Glucose levels are essential indicators of the health conditions of diabetics. Over the past decade, concerted efforts in various fields have led to significant advances in glucose monitoring technology. In particular, the rapid development of continuous glucose monitoring (CGM) based on electrochemical sensing principles has great potential to overcome the limitations of self-monitoring blood glucose (SMBG) in continuously tracking glucose trends, evaluating diabetes treatment options, and improving the quality of life of diabetics. However, the applications of minimally invasive electrochemical CGM sensors are still limited owing to the following aspects: i) invasiveness, ii) short lifespan, iii) biocompatibility, and iv) calibration and prediction. In recent years, the performance of minimally invasive electrochemical CGM systems (CGMSs) has been significantly improved owing to breakthrough developments in new materials and key technologies. In this review, we summarize the history of commercial CGMSs, the development of sensing principles, and the research progress of minimally invasive electrochemical CGM sensors in reducing the invasiveness of implanted probes, maintaining enzyme activity, and improving the biocompatibility of the sensor interface. In addition, this review also introduces calibration algorithms and prediction algorithms applied to CGMSs and describes the application of machine learning algorithms for glucose prediction.

A method for high-concentration agarose gel preparation and its application in high-resolution separation of low-molecular-weight nucleic acids and proteins

Separation of nucleic acids and proteins using gels has always been a crucial part of molecular biology research. For low-molecular-weight nucleic acids and proteins, low- and medium-concentration agarose gels cannot achieve the high resolution as polyacrylamide gels. We found that 6 %-14 % high-concentration agarose gels (HAGs) could be easily dissolved in an autoclave and the vertical gel cast can be effortlessly filled using an easy-made plastic box. Coupled with the improved buffer condition, HAG electrophoresis resulted in a good resolution of DNA and protein bands. With conventional TBE buffer plus 0.2 % NaCl, DNA fragments that differ by 2-5-bp within the 50-200-bp size range can be resolved on 6 %-8 % HAGs. By using TBE without NaCl, DNA fragments that differ by 2-bp or 2-nt within the 10-100-bp size range can be well resolved on >8 % HAGs. Using a buffer system comprising 1 M Tris-Cl for gel preparation, 0.2 M Tris-Cl/0.2 % SDS as upper tank buffer, and 0.2 M Tris-Cl as the lower tank buffer, HAGs achieved good molecular weight separation of total bacterial and plant proteins in the 10-200 kDa range. In conclusion, we developed a method for HAG preparation and electrophoresis of low-molecular-weight nucleic acids and proteins.

Climatic Chamber Stability Tests of Lipase-Catalytic Octyl-Sepharose Systems

The application of the climatic chamber presented in this paper to assess the storage stability of immobilized lipases is a new approach characterized by the potential of unifying the study conditions of biocatalysts created in various laboratories. The data achieved from storing lipases in the climatic chambers may be crucial for the chemical and pharmaceutical industry. Our paper describes the developed protocols for immobilization via interfacial activation of lipase B from Candida antarctica (CALB) and lipase OF from Candida rugosa (CRL-OF) on the Octyl-Sepharose CL-4B support. Optimization included buffers with different pH values of 4–9 and a wide range of ionic strength from 5 mM to 700 mM. It has been shown that the optimal medium for the CALB immobilization process on the tested support is a citrate buffer at pH 4 and high ionic strength of 500 mM. Implementing new optimal procedures enabled the hyperactivation of immobilized CALB (recovery activity 116.10 ± 1.70%) under the applicable reaction conditions using olive oil as a substrate. Importantly, CALB storage stability tests performed in a climatic chamber under drastic temperature and humidity conditions proved good stability of the developed biocatalyst (residual activity 218 ± 7.3% of dry form, after 7 days). At the same time, the low storage stability of CRL OF in a climatic chamber was demonstrated. It should be emphasized that the use of a climatic chamber to test the storage stability of a dry form of the studied lipases immobilized on Octyl-Sepharose CL-4B is, to our knowledge, described for the first time in the literature.

Cytophilic Agarose-Epoxide-Amine Cryogels Engineered with Granulated Microstructures

Inherent cytophobicity of agarose limits its direct use for the growth of anchorage-dependent cells. Here, we report a simple strategy allowing the development of agarose-based hydrogels entailed with both cytophilicity and microstructured morphology. Through the reaction of water-soluble 1,4-butanediol diglycidyl ether (BDDE) with trifunctional polyetheramine Jeffamine T403 in agarose solution followed by cryogelation of the mixtures, a series of macroporous agarose-epoxide-amine cryogels were prepared readily. Results from fluorescent labeling and energy-dispersive X-ray elemental mapping showed the formation of granulated microstructures in the cryogels. Such features closely correlated to the phase separation of BDDE-T403 polymers within the agarose matrix. Cytophilicity of the microstructured cryogels due to the integrated amine moieties was demonstrated through the adhesion of fibroblasts. Functional enrichment of the cryogels was further highlighted by leveraging the granulates as micro-reservoirs for polyphenol proanthocyanidin to enable antioxidation and protection of fibroblasts from H₂O₂-induced cytotoxic effect in vitro.

Thermally-modulated shape transition at the interface of soft gel filament and hydrophobic substrate

A liquid filament may pinch off into different shapes on interacting with a soft surface, as modulated by the interplay of inertial, capillary, and viscous forces. While similar shape transitions may intuitively be realized for more complex materials such as soft gel filaments as well, their intricate controllability towards deriving precise and stable morphological features remains challenging, as attributed to the complexities stemming from the underlying interfacial interactions over the relevant length and time scales during the sol-gel transition process. Circumventing these deficits in the reported literature, here we report a new means of precisely-controlled fabrication of gel microbeads via exploiting thermally-modulated instabilities of a soft filament atop a hydrophobic substrate. Our experiments reveal that abrupt morphological transitions of the gel material set in at a threshold temperature, resulting in spontaneous capillary thinning and filament breakup. We show that this phenomenon may be precisely modulated by an alteration in the hydration state of the gel material that may be preferentially dictated by its intrinsic glycerol content. Our results demonstrate that the consequent morphological transitions give rise to topologically-selective microbeads as an exclusive signature of the interfacial interactions of the gel material with the deformable hydrophobic interface underneath. Thus, intricate control may be imposed on the spatio-temporal evolution of the deforming gel, facilitating the inception of highly ordered structures of specific shapes and dimensionalities on demand. This is likely to advance the strategies of long shelf-life analytical biomaterial encapsulations via realizing one-step physical immobilization of bio-analytes on the bead surfaces as a new route to controlled materials processing, without demanding any resourced microfabrication facility or delicate consumable materials.

Mineralization of Lipase from Thermomyces lanuginosus Immobilized on Methacrylate Beads Bearing Octadecyl Groups to Improve Enzyme Features

Lipase from Thermomyces lanuginosus (TLL) has been immobilized on Purolite Lifetech® ECR8806F (viz. methacrylate macroporous resin containing octadecyl groups, designated as Purolite C18-TLL), and the enzyme performance has been compared to that of the enzyme immobilized on octyl-agarose, designated as agarose C8-TLL. The hydrolytic activity versus p-nitrophenol butyrate decreased significantly, and to a lower extent versus S-methyl mandelate (more than twofold), while versus triacetin and R-methyl mandelate, the enzyme activity was higher for the biocatalyst prepared using Purolite C18 (up to almost five-fold). Regarding the enzyme stability, Purolite C18-TLL was significantly more stable than the agarose C8-TLL. Next, the biocatalysts were mineralized using zinc, copper or cobalt phosphates. Mineralization increased the hydrolytic activity of Purolite C18-TLL versus triacetin and R-methyl mandelate, while this activity decreased very significantly versus the S-isomer, while the effects using agarose C8-TLL were more diverse (hydrolytic activity increase or decrease was dependent on the metal and substrate). The zinc salt treatment increased the stability of both biocatalysts, but with a lower impact for Purolite C18-TLL than for agarose-C8-TLL. On the contrary, the copper and cobalt salt treatments decreased enzyme stability, but more intensively using Purolite C18-TLL. The results show that even using enzymes immobilized following the same strategy, the differences in the enzyme conformation cause mineralization to have diverse effects on enzyme stability, hydrolytic activity, and specificity.

Systematic evaluation of agarose- and agar-based bioinks for extrusion-based bioprinting of enzymatically active hydrogels

Extrusion-based 3D bioprinting enables the production of customized hydrogel structures that can be employed in flow reactors when printing with enzyme-containing inks. The present study compares inks based on either low-melt agarose or agar at different concentrations (3-6%) and loaded with the thermostable enzyme esterase 2 from the thermophilic organism Alicyclobacillus acidocaldarius (AaEst2) with regard to their suitability for the fabrication of such enzymatically active hydrogels. A customized printer setup including a heatable nozzle and a cooled substrate was established to allow for clean and reproducible prints. The inks and printed hydrogel samples were characterized using rheological measurements and compression tests. All inks were found to be sufficiently printable to create lattices without overhangs, but printing quality was strongly enhanced at 4.5% polymer or more. The produced hydrogels were characterized regarding mechanical strength and diffusibility. For both properties, a strong correlation with polymer concentration was observed with highly concentrated hydrogels being more stable and less diffusible. Agar hydrogels were found to be more stable and show higher diffusion rates than comparable agarose hydrogels. Enzyme leaching was identified as a major drawback of agar hydrogels, while hardly any leaching from agarose hydrogels was detected. The poor ability of agar hydrogels to permanently immobilize enzymes indicates their limited suitability for their employment in perfused biocatalytic reactors. Batch-based activity assays showed that the enzymatic activity of agar hydrogels was roughly twice as high as the activity of agarose hydrogels which was mostly attributed to the increased amount of enzyme leaching. Agarose bioinks with at least 4.5% polymer were identified as the most suitable of the investigated inks for the printing of biocatalytic reactors with AaEst2. Drawbacks of these inks are limited mechanical and thermal stability, not allowing the operation of a reactor at the optimum temperature of AaEst2 which is above the melting point of the employed low-melt agarose.

Immobilization of Penicillin G Acylase on Vinyl Sulfone-Agarose: An Unexpected Effect of the Ionic Strength on the Performance of the Immobilization Process

Penicillin G acylase (PGA) from Escherichia coli was immobilized on vinyl sulfone (VS) agarose. The immobilization of the enzyme failed at all pH values using 50 mM of buffer, while the progressive increase of ionic strength permitted its rapid immobilization under all studied pH values. This suggests that the moderate hydrophobicity of VS groups is enough to transform the VS-agarose in a heterofunctional support, that is, a support bearing hydrophobic features (able to adsorb the proteins) and chemical reactivity (able to give covalent bonds). Once PGA was immobilized on this support, the PGA immobilization on VS-agarose was optimized with the purpose of obtaining a stable and active biocatalyst, optimizing the immobilization, incubation and blocking steps characteristics of this immobilization protocol. Optimal conditions were immobilization in 1 M of sodium sulfate at pH 7.0, incubation at pH 10.0 for 3 h in the presence of glycerol and phenyl acetic acid, and final blocking with glycine or ethanolamine. This produced biocatalysts with stabilities similar to that of the glyoxyl-PGA (the most stable biocatalyst of this enzyme described in literature), although presenting just over 55% of the initially offered enzyme activity versus the 80% that is recovered using the glyoxyl-PGA. This heterofuncionality of agarose VS beads opens new possibilities for enzyme immobilization on this support.

From Batch to Continuous Flow Bioprocessing: Use of an Immobilized γ-Glutamyl Transferase from B. subtilis for the Synthesis of Biologically Active Peptide Derivatives

γ-Glutamyl-peptides are frequently endowed with biological activities. In this work, "kokumi peptides" such as γ-glutamyl-methionine (1) and γ-glutamyl-(S)-allyl-cysteine (2), as well as the neuroprotective γ-glutamyl-taurine (3) and the antioxidant ophthalmic acid (4), were synthesized through an enzymatic transpeptidation reaction catalyzed by the γ-glutamyl transferase from Bacillus subtilis (BsGGT) using glutamine as the γ-glutamyl donor. BsGGT was covalently immobilized on glyoxyl-agarose resulting in high protein immobilization yield and activity recovery (>95%). Compounds 1-4 were obtained in moderate yields (19-40%, 5-10 g/L) with a variable purity depending on the presence of the main byproduct (γ-glutamyl-glutamine, 0-16%). To achieve process intensification and better control of side reactions, the synthesis of 2 was moved from batch to continuous flow. The specific productivity was 1.5 times higher than that in batch synthesis (13.7 μmol/min*g), but it was not accompanied by a paralleled improvement of the impurity profile.

Nano-fibrillated cellulose-based scaffolds for enzyme (co)-immobilization: Application to natural product glycosylation by Leloir glycosyltransferases

Polysaccharide-based scaffolds are promising carriers for enzyme immobilization. Here, we demonstrate a porous scaffold prepared by direct-ink-writing 3D printing of an ink consisting of nanofibrillated cellulose, carboxymethyl cellulose and citric acid for immobilization application. Negative surface charge introduced by the components made the scaffold amenable for an affinity-like immobilization via the cationic protein module Z_basic2. Z_basic2 fusions of two sugar nucleotide-dependent glycosyltransferases (C-glycosyltransferase, Z-CGT; sucrose synthase, Z-SuSy) were immobilized individually, or co-immobilized, and applied to synthesize the natural C-glycoside nothofagin. The cascade reaction involved β-C-glycosylation of phloretin (10 mM, ~90 % conversion) from UDP-glucose, provided from sucrose and catalytic amounts of UDP (1.0 mM). Enzymes were co-immobilized at ~65 mg protein/g carrier to receive activities of 9.5 U/g (Z-CGT) and 4.5 U/g (Z-SuSy) in 22-33 % yield (protein) and an effectiveness of 23 % (Z-CGT) and 13 % (Z-SuSy). The scaffold-bound enzymes were recyclable for 5 consecutive reactions.

Amphiphilic Nanointerface: Inducing the Interfacial Activation for Lipase

Graphene-based materials are widely used in the field of immobilized enzymes due to their easily tunable interfacial properties. We designed amphiphilic nanobiological interfaces between graphene oxide (GO) and lipase TL (Thermomyces lanuginosus) with tunable reduction degrees through molecular dynamics simulations and a facile chemical modulation, thus revealing the optimal interface for the interfacial activation of lipase TL and addressing the weakness of lipase TL, which exhibits weak catalytic activity due to an inconspicuous active site lid. It was demonstrated that the reduced graphene oxide (rGO) after 4 h of ascorbic acid reduction could boost the relative enzyme activity of lipase TL to reach 208%, which was 48% higher than the pristine GO and 120% higher than the rGO after 48 h of reduction. Moreover, TL-GO-4 h's tolerance against heat, organic solvent, and long-term storage environment was higher than that of free TL. The drawbacks of strong hydrophobic nanomaterials on lipase production were explored in depth with the help of molecular dynamics simulations, which explained the mechanism of enzyme activity enhancement. We demonstrated that nanomaterials with certain hydrophilicity could facilitate the lipase to undergo interfacial activation and improve its stability and protein loading rate, displaying the potential of the extensive application.

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.

Synthesis and Characterization of a New Cryogel Matrix for Covalent Immobilization of Catalase

The advantages of cryogels for enzyme immobilization applications include their mechanical and chemical robustness, ease of production, superior porosity, and low cost. Currently, many researchers are exploring porous material-based systems for enzyme immobilization that are more efficient and economically viable. Here, poly(2-Hydroxyethyl methacrylate-co-allyl glycidyl ether) (p(HEMA-co-AGE)) cryogel matrices were synthesized via the free radical cryopolymerization method to be employed as the support material. For the immobilization of the catalase enzyme onto the p(HEMA-co-AGE) cryogel matrix (catalase@p(HEMA-co-AGE), the best possible reaction conditions were determined by altering parameters such as pH, catalase initial concentration, and flow rate. The maximum catalase immobilization amount onto the p(HEMA-co-AGE) cryogel was found to be 48 mg/g cryogel. To determine the advantages of the cryogel matrix, e.g., the stability and reusability of the cryogel matrix, the adsorption–desorption cycles for the catalase enzyme were repeated five times using the same cryogel matrix. At the end of the reusability tests, it was found that the cryogel was very stable and maintained its adsorption capacity with the recovery ratio of 93.8 ± 1.2%. Therefore, the p(HEMA-co-AGE) cryogel matrix affords repeated useability, e.g., up to five times, without decreasing its catalase binding capacities significantly and has promising potential for many industrial applications. Cryogels offer clear distinctive advantages over common materials, e.g., micro/nano particles, hydrogels, films, and composites for these applications. At present, many researchers are working on the design of more effective and economically feasible, porous material-based systems for enzyme immobilization

Is enzyme immobilization a mature discipline? Some critical considerations to capitalize on the benefits of immobilization

Enzyme immobilization has been developing since the 1960s and although many industrial biocatalytic processes use the technology to improve enzyme performance, still today we are far from full exploitation of the field. One clear reason is that many evaluate immobilization based on only a few experiments that are not always well-designed. In contrast to many other reviews on the subject, here we highlight the pitfalls of using incorrectly designed immobilization protocols and explain why in many cases sub-optimal results are obtained. We also describe solutions to overcome these challenges and come to the conclusion that recent developments in material science, bioprocess engineering and protein science continue to open new opportunities for the future. In this way, enzyme immobilization, far from being a mature discipline, remains as a subject of high interest and where intense research is still necessary to take full advantage of the possibilities.

The applications of polysaccharides in dentistry

Polysaccharides are natural polymers widely present in animals, plants, and several microorganisms. Polysaccharides have remarkable properties, including easy extractions, degradability, and renewability, and have no apparent toxicity, making them ideal for biomedical applications. Moreover, polysaccharides are suitable for repairing oral tissue defects and treating oral diseases due to their excellent biocompatibility, biosafety, anti-inflammatory, and antibacterial properties. The oral cavity is a relatively complex environment vulnerable to numerous conditions, including soft tissue diseases, hard tissue disorders, and as well as soft and hard tissue diseases, all of which are complex to treat. In this article, we reviewed different structures of natural polysaccharides with high commercial values and their applications in treating various oral disease, such as drug delivery, tissue regeneration, material modification, and tissue repair.

Co-Immobilization of RizA Variants with Acetate Kinase for the Production of Bioactive Arginyl Dipeptides

The biocatalytic system comprised of RizA and acetate kinase (AckA) combines the specific synthesis of bioactive arginyl dipeptides with efficient ATP regeneration. Immobilization of this coupled enzyme system was performed and characterized in terms of activity, specificity and reusability of the immobilisates. Co-immobilization of RizA and AckA into a single immobilisate conferred no disadvantage in comparison to immobilization of only RizA, and a small addition of AckA (20:1) was sufficient for ATP regeneration. New variants of RizA were constructed by combining mutations to yield variants with increased biocatalytic activity and specificity. A selection of RizA variants were co-immobilized with AckA and used for the production of the salt-taste enhancers Arg-Ser and Arg-Ala and the antihypertensive Arg-Phe. The best variants yielded final dipeptide concentrations of 11.3 mM Arg-Ser (T81F_A158S) and 11.8 mM Arg-Phe (K83F_S156A), the latter of which represents a five-fold increase in comparison to the wild-type enzyme. T81F_A158S retained more than 50% activity for over 96 h and K83F_S156A for over 72 h. This study provides the first example of the successful co-immobilization of an l-amino acid ligase with an ATP-regenerating enzyme and paves the way towards a bioprocess for the production of bioactive dipeptides.

Lignocellulosic residues as supports for enzyme immobilization, and biocatalysts with potential applications

Growing demand for agricultural production means a higher quantity of residues produced. The reuse and recycling of agro-industrial wastes reduce worldwide greenhouse emissions. New opportunities are derived from this kind of residuals in the biotechnological field generating valuable products in growing sectors such as transportation, bioenergy, food, and feedstock. The use of natural macromolecules towards biocatalysts offers numerous advantages over free enzymes and friendliness with the environment. Enzyme immobilization improves enzyme properties (stability and reusability), and three types of supports are discussed: inorganic, organic, and hybrid. Several examples of agro-industrial wastes such as coconut wastes, rice husks, corn residues and brewers spent grains (BSG), their properties and potential as supports for enzyme immobilization are described in this work. Before the immobilization, biological and non-biological pretreatments could be performed to enhance the waste potential as a carrier. Additionally, immobilization methods such as covalent binding, adsorption, cross-linking and entrapment are compared to provide high efficiency. Enzymes and biocatalysts for industrial applications offer advantages over traditional chemical processes with respect to sustainability and process efficiency in food, energy, and bioremediation fields. The wastes reviewed in this work demonstrated a high affinity for lipases and laccases and might be used in biodiesel production and textile wastewater treatment, among other applications.

Evaluation of MxOy/fucoidan hybrid system and their application in lipase immobilization process

In this work, new M_xO_y/fucoidan hybrid systems were fabricated and applied in lipase immobilization. Magnesium (MgO) and zirconium (ZrO₂) oxides were used as M_xO_y inorganic matrices. In the first step, the proposed oxides were functionalized with fucoidan from Fucus vesiculosus (Fuc). The obtained MgO/Fuc and ZrO₂/Fuc hybrids were characterized by means of spectroscopic analyses, including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance. Additionally, thermogravimetric analysis was performed to determine the thermal stability of the hybrids. Based on the results, the mechanism of interaction between the oxide supports and fucoidan was also determined. Furthermore, the fabricated M_xO_y/fucoidan hybrid materials were used as supports for the immobilization of lipase from Aspergillus niger, and a model reaction (transformation of p-nitrophenyl palmitate to p-nitrophenol) was performed to determine the catalytic activity of the proposed biocatalytic system. In that reaction, the immobilized lipase exhibited high apparent and specific activity (145.5 U/g_catalyst and 1.58 U/mg_enzyme for lipase immobilized on MgO/Fuc; 144.0 U/g_catalyst and 2.03 U/mg_enzyme for lipase immobilized on ZrO₂/Fuc). The immobilization efficiency was also confirmed using spectroscopic analyses (FTIR and XPS) and confocal microscopy.

Polymeric Hydrogels for In Vitro 3D Ovarian Cancer Modeling

Ovarian cancer (OC) grows and interacts constantly with a complex microenvironment, in which immune cells, fibroblasts, blood vessels, signal molecules and the extracellular matrix (ECM) coexist. This heterogeneous environment provides structural and biochemical support to the surrounding cells and undergoes constant and dynamic remodeling that actively promotes tumor initiation, progression, and metastasis. Despite the fact that traditional 2D cell culture systems have led to relevant medical advances in cancer research, 3D cell culture models could open new possibilities for the development of an in vitro tumor microenvironment more closely reproducing that observed in vivo. The implementation of materials science and technology into cancer research has enabled significant progress in the study of cancer progression and drug screening, through the development of polymeric scaffold-based 3D models closely recapitulating the physiopathological features of native tumor tissue. This article provides an overview of state-of-the-art in vitro tumor models with a particular focus on 3D OC cell culture in pre-clinical studies. The most representative OC models described in the literature are presented with a focus on hydrogel-based scaffolds, which guarantee soft tissue-like physical properties as well as a suitable 3D microenvironment for cell growth. Hydrogel-forming polymers of either natural or synthetic origin investigated in this context are described by highlighting their source of extraction, physical-chemical properties, and application for 3D ovarian cancer cell culture.

Enzyme Immobilization and Co-Immobilization: Main Framework, Advances and Some Applications

Enzymes are outstanding (bio)catalysts, not solely on account of their ability to increase reaction rates by up to several orders of magnitude but also for the high degree of substrate specificity, regiospecificity and stereospecificity. The use and development of enzymes as robust biocatalysts is one of the main challenges in biotechnology. However, despite the high specificities and turnover of enzymes, there are also drawbacks. At the industrial level, these drawbacks are typically overcome by resorting to immobilized enzymes to enhance stability. Immobilization of biocatalysts allows their reuse, increases stability, facilitates process control, eases product recovery, and enhances product yield and quality. This is especially important for expensive enzymes, for those obtained in low fermentation yield and with relatively low activity. This review provides an integrated perspective on (multi)enzyme immobilization that abridges a critical evaluation of immobilization methods and carriers, biocatalyst metrics, impact of key carrier features on biocatalyst performance, trends towards miniaturization and detailed illustrative examples that are representative of biocatalytic applications promoting sustainability.

Study of Several Alginate-Based Hydrogels for In Vitro 3D Cell Cultures

Hydrogel, a special system of polymer solutions, can be obtained through the physical/chemical/enzymic crosslinking of polymer chains in a water-based dispersion medium. Different compositions and crosslinking methods endow hydrogel with diverse physicochemical properties. Those hydrogels with suitable physicochemical properties hold manifold functions in biomedical fields, such as cell transplantation, tissue engineering, organ manufacturing, drug releasing and pathological model analysis. In this study, several alginate-based composite hydrogels, including gelatin/alginate (G-A), gelatin/alginate/agarose (G-A-A), fibrinogen/alginate (F-A), fibrinogen/alginate/agarose (F-A-A) and control alginate (A) and alginate/agarose (A-A), were constructed. We researched the advantages and disadvantages of these hydrogels in terms of their microscopic structure (cell living space), water holding capacity, swelling rate, swelling–erosion ratio, mechanical properties and biocompatibility. Briefly, alginate-based hydrogels can be used for three-dimensional (3D) cell culture alone. However, when mixed with other natural polymers in different proportions, a relatively stable network with a good cytocompatibility, mechanical strength and water holding capacity can be formed. The physical and chemical properties of the hydrogels can be adjusted by changing the composition, proportion and cross-linking methods of the polymers. Conclusively, the G-A-A and F-A-A hydrogels are the best hydrogels for the in vitro 3D cell cultures and pathological model construction.