Biomimetic and biopolymer-based enzyme encapsulation

Novel pH- and thermal-responsive oleogel capsules: Featuring an oleogel core and ultrathin calcium-alginate shell

Oleogels have been explored as a new lipid-based delivery system, however, their insolubility and unsuitable shape severely limit their application in food systems. Herein, core-shell oleogel capsules with high monodispersity (coefficient variation (CV) < 5%)) were prepared via gravity-assisted co-flowing microfluidic device and simply air-drying. The oleogel capsules with oleogel core and ultrathin calcium-alginate shell were prepared. Oleogel capsules maintained their original shape at pH = 2.0 but swelled rapidly at pH = 6.8 and 7.4. The swelling ratio of shell can be adjusted by inner fluid flow rate (Qin). Notably, the core with beeswax (BW) crystal network, effectively improved the stability performances and also could provide thermal response. Finally, the oleogel capsules demonstrated excellent sustained release and UV protection of lipophilic bioactives. This work sheds light on development of novel oleogel capsules, making them ideal candidates for smart food encapsulation applications.

An Atomistic View on the Mechanism of Diatom Peptide-Guided Biomimetic Silica Formation

Deciphering nature's remarkable way of encoding functions in its biominerals holds the potential to enable the rational development of nature-inspired materials with tailored properties. However, the complex processes that convert solution-state precursors into solid biomaterials remain largely unknown. In this study, an unconventional approach is presented to characterize these precursors for the diatom-derived peptides R5 and synthetic Silaffin-1A1 (synSil-1A1). These molecules can form defined supramolecular assemblies in solution, which act as templates for solid silica structures. Using a tailored structural biology toolbox, the structure-function relationships of these self-assemblies are unveiled. NMR-derived constraints are employed to enable a recently developed fractal-cluster formalism and then reveal the architecture of the peptide assemblies in atomistic detail. Finally, by monitoring the self-assembly activities during silica formation at simultaneous high temporal and residue resolution using real-time spectroscopy, the mechanism is elucidated underlying template-driven silica formation. Thus, it is demonstrated how to exercise morphology control over bioinorganic solids by manipulating the template architectures. It is found that the morphology of the templates is translated into the shape of bioinorganic particles via a mechanism that includes silica nucleation on the solution-state complexes' surfaces followed by complete surface coating and particle precipitation.

Neuroprotective effects of platinum nanoparticle-based microreactors in bicuculline-induced seizures

Epilepsy designates a group of chronic brain disorders, characterized by the recurrence of hypersynchronous, repetitive activity, of neuronal clusters. Epileptic seizures are the hallmark of epilepsy. The primary goal of epilepsy treatment is to eliminate seizures with minimal side effects. Nevertheless, approximately 30% of patients do not respond to the available drugs. An imbalance between excitatory/inhibitory neurotransmission, that leads to excitotoxicity, seizures, and cell death, has been proposed as an important mechanism regarding epileptogenesis. Recently, it has been shown that microreactors composed of platinum nanoparticles (Pt-NP) and glutamate dehydrogenase possess in vitro and in vivo activity against excitotoxicity. This study investigates the in vivo effects of these microreactors in an animal model of epilepsy induced by the administration of the GABAergic antagonist bicuculline. Male Wistar rats were administered intracerebroventricularly (i.c.v.) with the microreactors or saline and, five days later, injected with bicuculline or saline. Seizure severity was evaluated in an open field. Thirty min after behavioral measurements, animals were euthanized, and their brains processed for neurodegeneration evaluation and for neurogenesis. Treatment with the microreactors significantly increased the time taken for the onset of seizures and for the first tonic-clonic seizure, when compared to the bicuculline group that did not receive the microreactor. The administration of the microreactors also increased the time spent in total exploration and grooming. Treatment with the microreactors decreased bicuculline-induced neurodegeneration and increased neurogenesis in the dorsal and ventral hippocampus. These observations suggest that treatment with Pt-NP-based microreactors attenuates the behavioral and neurobiological consequences of epileptiform seizure activity.

Improving the thermal stability of phytase using core-shell hydrogel beads

A core-shell hydrogel bead system was designed to maintain the catalytic activity of phytase and protect its enzymatic functionality from heat treatment. The designed structure consists of a chitosan-phytase complex core and an alginate-carrageenan hydrogel shell. The core-shell hydrogel was optimized to improve phytase encapsulation efficiency and increase the thermal stability of the encapsulated phytase. After heat treatment, encapsulated phytase retained ∼ 70 % of its catalytic activity and the same secondary structure of free phytase. Fourier transform infrared spectroscopy indicated strong intermolecular interactions between chitosan and phytase in the core, but little interaction between the core and the alginate and κ-carrageenan shell, this supports the structural and functional stability of the phytase. Differential scanning calorimetry confirmed that the designed core-shell structure had a higher melting point. Encapsulating phytase in a core-shell hydrogel bead can enhance the thermal stability of phytase, which broadens the potential applications for phytase delivery.

Potential utility of bacterial protein nanoreactor for sustainable in-situ biocatalysis in wide range of bioprocess conditions

Bacterial microcompartments (MCPs) are proteinaceous organelles that natively encapsulates the enzymes, substrates, and cofactors within a protein shell. They optimize the reaction rates by enriching the substrate in the vicinity of enzymes to increase the yields of the product and mitigate the outward diffusion of the toxic or volatile intermediates. The shell protein subunits of MCP shell are selectively permeable and have specialized pores for the selective inward diffusion of substrates and products release. Given their attributes, MCPs have been recently explored as potential candidates as subcellular nano-bioreactor for the enhanced production of industrially important molecules by exercising pathway encapsulation. In the current study, MCPs have been shown to sustain enzyme activity for extended periods, emphasizing their durability against a range of physical challenges such as temperature, pH and organic solvents. The significance of an intact shell in conferring maximum protection is highlighted by analyzing the differences in enzyme activities inside the intact and broken shell. Moreover, a minimal synthetic shell was designed with recruitment of a heterologous enzyme cargo to demonstrate the improved durability of the enzyme. The encapsulated enzyme was shown to be more stable than its free counterpart under the aforementioned conditions. Bacterial MCP-mediated encapsulation can serve as a potential strategy to shield the enzymes used under extreme conditions by maintaining the internal microenvironment and enhancing their cycle life, thereby opening new means for stabilizing, and reutilizing the enzymes in several bioprocess industries.

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

Hydrogel-enzyme micropatch array format for chemical mapping: A proof of concept

Conventional sensing methods report on concentrations of analytes in a single point of sampled medium or provide an average value. However, distributions of substances on surfaces of sampled objects often exhibit intricate inhomogeneities. In order to obtain snapshots of the chemical distributions on surfaces, we have developed enzyme-loaded hydrogel arrays (5 × 5 and 10 × 10). The acrylic 10 × 10 array base contains 100 holes, which are filled with agarose hydrogel containing assay enzymes and substrates. Such arrays can be exposed to the analyzed surfaces to collect minute amounts of analytes. Following a brief incubation, they are subsequently visualized in a custom-built array reader device. The reader incorporates a light-emitting diode-based light source, miniature camera, and Raspberry Pi single-board computer. Two Python programs capture and analyze the images of the array to extract pixel saturation values corresponding to individual hydrogel micropatches. The method has been thoroughly optimized for mapping of glucose and lactic acid. The optimized parameters were: contact time, agarose concentration, substrate concentration, enzyme concentration ratio, and enzyme concentration. The array biosensor was further tested by mapping glucose distribution in fruit/vegetable cross-sections (apple, guava, and cucumber) and lactic acid distribution in cheese. We think that this new hydrogel-based chemical mapping method can find applications in studies related to food science, plant physiology, clinical chemistry, and forensics; wherever the distributions of analytes on the tested surfaces need to be assessed.

Glucose oxidase and metal catalysts combined tumor synergistic therapy: mechanism, advance and nanodelivery system

Cancer has always posed a significant threat to human health, prompting extensive research into new treatment strategies due to the limitations of traditional therapies. Starvation therapy (ST) has garnered considerable attention by targeting the primary energy source, glucose, utilized by cancer cells for proliferation. Glucose oxidase (GOx), a catalyst facilitating glucose consumption, has emerged as a critical therapeutic agent for ST. However, mono ST alone struggles to completely suppress tumor growth, necessitating the development of synergistic therapy approaches. Metal catalysts possess enzyme-like functions and can serve as carriers, capable of combining with GOx to achieve diverse tumor treatments. However, ensuring enzyme activity preservation in normal tissue and activation specifically within tumors presents a crucial challenge. Nanodelivery systems offer the potential to enhance therapy effectiveness by improving the stability of therapeutic agents and enabling controlled release. This review primarily focuses on recent advances in the mechanism of GOx combined with metal catalysts for synergistic tumor therapy. Furthermore, it discusses various nanoparticles (NPs) constructs designed for synergistic therapy in different carrier categories. Finally, this review provides a summary of GOx-metal catalyst-based NPs (G-M) and offers insights into the challenges associated with G-M therapy, delivery design, and oxygen (O2) supply.

Alginate-based materials for enzyme encapsulation

Enzymes are widely used in industry due to their high efficiency and selectivity. However, their low stability during certain industrial processes can result in a significant loss of catalytic activity. Encapsulation is a promising technique that can stabilize enzymes by protecting them from environmental stresses such as extreme temperature and pH, mechanical force, organic solvents, and proteases. Alginate and alginate-based materials have emerged as effective carriers for enzyme encapsulation due to their biocompatibility, biodegradability, and ability to form gel beads through ionic gelation. This review presents various alginate-based encapsulation systems for enzyme stabilization and explores their applications in different industries. We discuss the preparation methods of alginate encapsulated enzymes and analyze the release mechanisms of enzymes from alginate materials. Additionally, we summarize the characterization techniques used for enzyme-alginate composites. This review provides insights into the use of alginate encapsulation as a means of stabilizing enzymes and highlights the potential benefits for various industrial applications.

Fluorinated dendritic amphiphiles, their stomatosome aggregates and application in enzyme encapsulation

Enzymes are more selective and efficient than synthetic catalysts but are limited by difficult recycling. This is overcome by immobilisation, namely through encapsulation, with the main drawback of this method being slow diffusion of products and reactants, resulting in effectively lowered enzyme activity. Fluorinated dendritic amphiphiles were reported to self-assemble into regularly perforated bilayer vesicles, so-called "stomatosomes". It was proposed that they could be promising novel reaction vessels due to their increased porosity while retaining larger biomolecules at the same time. Amphiphiles were synthesised and their aggregation was analysed by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) in buffered conditions necessary for enzyme encapsulation. Urease and albumin were encapsulated using the thin-film hydration method and investigated by confocal and time-gated stimulated emission depletion microscopy (gSTED). Their release was then used to probe the selective retention of cargo by stomatosomes. Free and encapsulated enzyme activity were compared and their capacity to be reused was evaluated using the Berthelot method. Urease was successfully encapsulated, did not leak out at room temperature, and showed better activity in perforated vesicles than in closed vesicles without perforations. Encapsulated enzyme could be reused with retained activity over 8 cycles using centrifugation, while free enzyme had to be filtrated. These results show that stomatosomes may be used in enzyme immobilisation applications and present advantages over closed vesicles or free enzyme.

Understanding Self-Assembly of Silica-Precipitating Peptides to Control Silica Particle Morphology

The most advanced materials are those found in nature. These evolutionary optimized substances provide highest efficiencies, e.g., in harvesting solar energy or providing extreme stability, and are intrinsically biocompatible. However, the mimicry of biological materials is limited to a few successful applications since there is still a lack of the tools to recreate natural materials. Herein, such means are provided based on a peptide library derived from the silaffin protein R5 that enables rational biomimetic materials design. It is now evident that biomaterials do not form via mechanisms observed in vitro. Instead, the material's function and morphology are predetermined by precursors that self-assemble in solution, often from a combination of protein and salts. These assemblies act as templates for biomaterials. The RRIL peptides used here are a small part of the silica-precipitation machinery in diatoms. By connecting RRIL motifs via varying central bi- or trifunctional residues, a library of stereoisomers is generated, which allows characterization of different template structures in the presence of phosphate ions by combining residue-resolved real-time NMR spectroscopy and molecular dynamics (MD) simulations. Understanding these templates in atomistic detail, the morphology of silica particles is controlled via manipulation of the template precursors.

pH-Sensitive Twin Liposomes Containing Quercetin and Laccase for Tumor Therapy

In this study, functional twin liposomes (TLs) were designed by linking avidin-anchored single liposomes and biotin-anchored single liposomes via avidin-biotin interactions. Here, we first punched a hole on the liposome surface using the liposome magnetoporation method to prepare functional single liposomes, which were used for safely encapsulating quercetin (QER, as a model prodrug) or laccase (LAC, as a bioactive enzyme) inside the liposomes without the use of organic solvents; the pores were then plugged by pH-sensitive glycol chitosan grafted with 3-diethylaminopropylamine (GDEAP) and avidin (or biotin). As a result, single liposomes with QER and biotin-GDEAP were efficiently coupled with other liposomes with LAC and avidin-GDEAP. We demonstrated that the TLs could accelerate QER and LAC release at acidic pH (6.8), improving the LAC-mediated oxidization of QER and significantly elevating tumor cell death, suggesting that this strategy can be used as an efficient method for the programmed action of prodrugs.

Recent advancements in encapsulation of chitosan-based enzymes and their applications in food industry

Enzymes are readily inactivated in harsh micro-environment due to changes in pH, temperature, and ionic strength. Developing suitable and feasible techniques for stabilizing enzymes in food sector is critical for preventing them from degradation. This review provides an overview on chitosan (CS)-based enzymes encapsulation techniques, enzyme release mechanisms, and their applications in food industry. The challenges and future prospects of CS-based enzymes encapsulation were also discussed. CS-based encapsulation techniques including ionotropic gelation, emulsification, spray drying, layer-by-layer self-assembly, hydrogels, and films have been studied to improve the encapsulation efficacy (EE), heat, acid and base stability of enzymes for their applications in food, agricultural, and medical industries. The smart delivery design, new delivery system development, and in vivo releasing mechanisms of enzymes using CS-based encapsulation techniques have also been evaluated in laboratory level studies. The CS-based encapsulation techniques in commercial products should be further improved for broadening their application fields. In conclusion, CS-based encapsulation techniques may provide a promising approach to improve EE and bioavailability of enzymes applied in food industry.HighlightsEnzymes play a critical role in food industries but susceptible to inactivation.Chitosan-based materials could be used to maintain the enzyme activity.Releasing mechanisms of enzymes from encapsulators were outlined.Applications of encapsulated enzymes in food fields was discussed.

Nano-Scaled Materials and Polymer Integration in Biosensing Tools

The evolution of biosensors and diagnostic devices has been thriving in its ability to provide reliable tools with simplified operation steps. These evolutions have paved the way for further advances in sensing materials, strategies, and device structures. Polymeric composite materials can be formed into nanostructures and networks of different types, including hydrogels, vesicles, dendrimers, molecularly imprinted polymers (MIP), etc. Due to their biocompatibility, flexibility, and low prices, they are promising tools for future lab-on-chip devices as both manufacturing materials and immobilization surfaces. Polymers can also allow the construction of scaffold materials and 3D structures that further elevate the sensing capabilities of traditional 2D biosensors. This review discusses the latest developments in nano-scaled materials and synthesis techniques for polymer structures and their integration into sensing applications by highlighting their various structural advantages in producing highly sensitive tools that rival bench-top instruments. The developments in material design open a new door for decentralized medicine and public protection that allows effective onsite and point-of-care diagnostics.

Inverting glucuronidation of hymecromone in situ by catalytic nanocompartments

Glucuronidation is a metabolic pathway that inactivates many drugs including hymecromone. Adverse effects of glucuronide metabolites include a reduction of half-life circulation times and rapid elimination from the body. Herein, we developed synthetic catalytic nanocompartments able to cleave the glucuronide moiety from the metabolized form of hymecromone in order to convert it to the active drug. By shielding enzymes from their surroundings, catalytic nanocompartments favor prolonged activity and lower immunogenicity as key aspects to improve the therapeutic solution. The catalytic nanocompartments (CNCs) consist of self-assembled poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) diblock copolymer polymersomes encapsulating β-glucuronidase. Insertion of melittin in the synthetic membrane of these polymersomes provided pores for the diffusion of the hydrophilic hymecromone-glucuronide conjugate to the compartment inside where the encapsulated β-glucuronidase catalyzed its conversion to hymecromone. Our system successfully produced hymecromone from its glucuronide conjugate in both phosphate buffered solution and cell culture medium. CNCs were non-cytotoxic when incubated with HepG2 cells. After being taken up by cells, CNCs produced the drug in situ over 24 hours. Such catalytic platforms, which locally revert a drug metabolite into its active form, open new avenues in the design of therapeutics that aim at prolonging the residence time of a drug.

Tamarindus indica seed-shell nanoparticles‑silver nanoparticles-Ceratonia silique bean gum composite for copper-micro mesh grid electrode fabrication and its application for glucose detection in artificial salivary samples

This study used a new approach to fabricate a glucose detection system based on nano-engineered biomaterials. The fabrication steps included strategic synthesis, integration and stabilization of biological and metal nanoparticles in superabsorbent hydrogel gum matrix. The design of the high-performance electrochemical biosensor platform includes copper-micro mesh grid electrode modified with polymer phase comprising of silver nanoparticles surface coroneted with Ceratonia silique locust bean gum (LBG), Tamarindus indica seed-shell nanoparticles and glucose oxidase (GOx). Fundamental assessment of catalytic properties of the nanobiocomposite films on copper grid probe were performed by cyclic voltammetry, amperometry, differential pulse voltammetry. Probes showed good repeatability, reproducibility, selectivity, and long-term stability. The GOx was well-immobilized and stabilized by C. siliqua nano-matrix, with 85% and 98% activity retention when stored at different condiions for 6 month and 3 months, respectively. The fabricated grid-platform exhibited linear response in a wide range of glucose concentration, with detection limit of 1.0 nM (S/N = 3) and sensitivity 38.7 mA nM^-1 cm^-2. The bionanomaterial-based sensor was successfully applied for ultra-low glucose detection in artificial salivary samples. The designed sensor, perhaps with further modifications, has potential for the next generation of sensing platform in various biological fluids especially for non-invasive glucose detection for diabetic patients.

Biomimetic Silica Encapsulation of Lipid Nanodiscs and β-Sheet-Stabilized Diacylglycerol Kinase

Integral membrane proteins (IMPs) comprise highly important classes of proteins such as transporters, sensors, and channels, but their investigation and biotechnological application are complicated by the difficulty to stabilize them in solution. We set out to develop a biomimetic procedure to encapsulate functional integral membrane proteins in silica to facilitate their handling under otherwise detrimental conditions and thereby extend their applicability. To this end, we designed and expressed new fusion constructs of the membrane scaffold protein MSP with silica-precipitating peptides based on the R5 sequence from the diatom Cylindrotheca fusiformis. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that membrane lipid nanodiscs surrounded by our MSP variants fused to an R5 peptide, so-called nanodiscs, were formed. Exposing them to silicic acid led to silica-encapsulated nanodiscs, a new material for stabilizing membrane structures and a first step toward incorporating membrane proteins in such structures. In an alternative approach, four fusion constructs based on the amphiphilic β-sheet peptide BP-1 and the R5 peptide were generated and successfully employed toward silica encapsulation of functional diacylglycerol kinase (DGK). Silica-encapsulated DGK was significantly more stable against protease exposure and incubation with simulated gastric fluid (SGF) and intestinal fluid (SIF).