Amino functionalization of carboxymethyl cellulose for efficient immobilization of urease

Optimization of immobilized urease enzyme on porous polymer for enhancing the stability, reusability and enzymatic kinetics using response surface methodology

The study examines the immobilization of the urease enzyme on a range of High Internal Phase Emulsion (polyHIPE) materials, assessing characteristics, efficiency, and performance. It also investigates the impact of polyHIPE type, quantity, incubation time, and various parameters on the process and enzyme activity. Surface morphology and functional groups of polyHIPE materials were determined through scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR) analyses, revealing significant alterations after modification with polyglutaraldehyde (PGA). The maximum immobilization efficiency of 95% was achieved by adding PGA to polyHIPE materials with an incubation period of 15 h. The optimized conditions for immobilized enzyme using a Box-Behnken design (BBD) of response surface methodology (RSM) were as follows: temperature (40.8 °C), pH (7.1) and NaCl concentration (0.007 g/L). Furthermore, the immobilized enzyme demonstrated remarkable reusability, retaining 75% of its initial activity after six cycles, and sustained shelf-life stability, retaining over 40% activity after 10 days at room temperature. Kinetic analyses revealed that immobilized urease exhibited higher affinity for the substrate, but lower rate of substrate conversion compared to the free enzyme. These findings offer valuable insights into optimizing urease immobilization processes and enhancing urease stability and activity, with potential applications in various fields, including biotechnology and biocatalysis.

Poly(acrylamide)-co-poly(hydroxyethyl)methacrylate-co-poly(cyclohexyl methacrylate) hydrogel platform for stability, storage and biocatalytic applications of urease

In our present work, an explicit crosslinked thermo-responsive hydrogel platform has been developed, by using polyacrylamide (PAAm), poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(cyclohexyl methacrylate) (PCHMA), and then coupled with urease to yield bioconjugates (BCs). Synergic effect of these polymer units provides thermoresponsive nature, optimum crosslinking with desired swelling behaviour, and stability and improved catalytic to Urease in the resultant BCs. Synthesis of the terpolymer has been achieved by employing HEMA (monomer as well as crosslinker), instead of using the conventional crosslinkers, through free radical solution polymerization technique. Various grades of TRPUBs have been fabricated by varying HEMA and CHMA contents while keeping fixed amounts of AAm. Further, the structural analysis of BCs has been done by fourier transform infra-red spectroscopic study and their thermal stabilities have been studied by thermogravimetric analysis. Urea present in TRPUBs has beenanalysed for its hydrolysis atdifferent temperatures viz., 25 °C, 45 °C and 70 °C. Further, the effect of crosslinking, temperature and reaction time on catalytic activities of TRPUBs has been studied. TRPUBs grades have showna maximum swelling capacity up to 5200 %; excellent catalytic activity even at 70 °C; and 85 % activity retention after 18 days storage in buffer medium.

Ammonium release in synthetic and human urine by a urease immobilized nanoconstruct

In this work, we have studied the ability of urease immobilized on glutaraldehyde crosslinked chitosan coated magnetic iron oxide nanoparticles (Urease/GA/CS/MIONPs), for the hitherto unreported comparative hydrolysis of urea in synthetic (SUr) and real human urine (HUr). The prepared Urease/GA/CS/MIONPs were characterized by a combination of Fourier transform infrared spectroscopy (FTIR), field emission-scanning-electron-microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and dynamic light scattering (DLS). The nanoconstructs display the highest ammonium ion liberation post-urea hydrolysis in 1/20 or 1/24-fold dilutions of SUr and HUr, respectively. The optimum activity of immobilized urease is observed at pH 7, and the nanoconstructs facilitate efficient urea-hydrolysis till at least 45 °C. Kinetic analysis of the immobilized urease shows km and vmax of 14.81 mM, 12.36 mM, and 18.55 μM min-1 and 10.10 μM min-1, towards SUr and HUr, respectively. The magnetization of the immobilized urease is suitable for reuse across multiple cycles of urea hydrolysis in SUr and HUr. The robust performance of Urease/GA/CS/MIONPs in SUr and HUr is promising for generating ammonium as a useable source of nitrogen from human urine, and underscores the suitability of SUr as a urine mimic for such interventions.

Fluorescence-enhanced detection of hypochlorite based on in situ synthesis of functionalization-free carbon spheres

Hypochlorite (ClO-) exposure has been confirmed to be associated with many serious diseases. Although abundant organic molecule-based probes have demonstrated high sensitivity and selectivity for ClO- response, they often suffer from limitations including tedious preparation steps, poor water solubility, and the use of toxic solvent. In this work, a novel fluorescent sensor based on carbon spheres (CS) synthesized by solvothermal method was presented for ClO- detection. In the presence of ClO-, the obtained micro-size CS that initially displayed very weak fluorescence experienced a significant fluorescence enhancement in the blue channel, and a linear response range of 2-110 μM with detection limit of 10.7 nM could be achieved. In addition to proposed mechanism verification, a field visualization platform based on smartphone was designed to monitor hypochlorite in real environmental water samples to demonstrate its potential in portable detection.

Removal of urea in ultrapure water system by urease-coated reverse osmosis membrane

Among the various substances found in the feed source for the production of ultrapure water (UPW), urea is challenging to remove because it is a small molecular weight molecule that is not easily oxidized and does not carry a charge under neutral pH conditions. Urease enzyme, found in various organisms such as plants and bacteria, catalyze the hydrolysis of urea into carbon dioxide and ammonia. In this study, urease was immobilized on the polyamide layer of a reverse osmosis (RO) membrane to remove urea in UPW systems. The removal efficiency of urea by urease-coated RO membrane showed up to 27.9 % higher urea removal efficiency compared to the pristine membrane. This increase in urea removal can be attributed to both physical and biological effects from the urease coating on the membrane. Firstly, urease on the membrane surface can act as an additional physical barrier for urea to pass through. Secondly, urea can be hydrolyzed by the enzyme when it passes through the urease-coated RO membrane. In a two-pass RO system typical for UPW production, the removal of urea by a urease-coated membrane would be enhanced by twofold. This overall method can significantly increase the removal efficiency of urea in UPW systems, especially when considering the compounded removal by the urease coating, rejection by RO, and additional reactions by other treatment processes. Moreover, urea in UPW systems can be removed without the installment of additional processes by simply coating urease on the existing RO membranes.

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.

Sonochemical preparation of folate-decorated reductive-responsive carboxymethylcellulose-based nanocapsules for targeted drug delivery

In this study, a biocompatible folate-decorated reductive-responsive carboxymethylcellulose-based nanocapsules (FA-RCNCs) were designed and prepared via sonochemical method for targeted delivery and controlled release of hydrophobic drugs. The shell of FA-RCNCs was cross-linked by disulfide bonds formed from hydrosulfuryl groups on the thiolated carboxymethylcellulose (TCMC) and encapsulated hydrophobic drug dispersed in the oil phase into nanocapsules. Moreover, the size and morphology of drug loaded FA-RCNCs were characterized by DLS, SEM and CLSM which indicated that the synthesized nanocapsules have suitable size range and excellent stability for circulating in the bloodstream. The drug release rate of FA-RCNCs could be controlled by adjusting their sizes and shell thickness, which could be dominated by the concentration of TCMC and sonochemical conditions. Furthermore, the obtained FA-RCNCs could be ingested into Hela cells via folate-receptor (FR)-mediated endocytosis and quickly release drugs under reductive environment, which demonstrated that FA-RCNCs could become potential hydrophobic drugs carries for cancer therapy.

Cellulose supported magnetic nanohybrids: Synthesis, physicomagnetic properties and biomedical applications-A review

Cellulose and its forms are widely used in biomedical applications due to their biocompatibility, biodegradability and lack of cytotoxicity. It provides ample opportunities for the functionalization of supported magnetic nanohybrids (CSMNs). Because of the abundance of surface hydroxyl groups, they are surface tunable in either homogeneous or heterogeneous solvents and thus act as a substrate or template for the CSMNs' development. The present review emphasizes on the synthesis of various CSMNs, their physicomagnetic properties, and potential applications such as stimuli-responsive drug delivery systems, MRI, enzyme encapsulation, nucleic acid extraction, wound healing and tissue engineering. The impact of CSMNs on cytotoxicity, magnetic hyperthermia, and folate-conjugates is highlighted in particular, based on their structures, cell viability, and stability. Finally, the review also discussed the challenges and prospects of CSMNs' development. This review is expected to provide CSMNs' development roadmap in the context of 21st-century demands for biomedical therapeutics.

Immobilization of Purified Pectin Lyase from Acinetobacter calcoaceticus onto Magnetic Carboxymethyl Cellulose Nanoparticles and Its Usability in Food Industry

An important component of the pectinase enzyme complex is pectin lyase (polymethylgalacturonate lyase; EC 4.2.2.10). In this study, extracellular pectin lyase enzyme was produced from Acinetobacter calcoaceticus bacteria. Pectin lyase was then purified using three-phase precipitation (TPP) technique with 25.5% yield. The pectin lyase was immobilized covalently via the L-glutaraldehyde spacer to the carboxymethyl cellulose. The immobilized pectin lyase was magnetized using Fe3O4 nanoparticles. Purified pectin lyase was connected to magnetized support material after 90 min at the rate of 80%. The most appropriate immobilization conditions were determined as pH 8 and 30°C. By characterizing the free and immobilized enzyme, KM, Vmax, and optimum pH and optimum temperature values were determined. It was optimum pH 8 and temperature 50°C for both free and immobilized pectin lyase. The structural characterization of the immobilized pectin lyase modified with Fe3O4 nanoparticles was carried out by SEM, FT-IR, and XRD chromatographic analyses. At the end of the study, free and immobilized enzymes were used for purification of some fruit juices and results were compared.

Recent advances in composites based on cellulose derivatives for biomedical applications

Cellulose derivatives represent a viable alternative to pure cellulose due to their solubility in water and common organic solvents. This, coupled with their low cost, biocompatibility, and biodegradability, makes them an attractive choice for applications related to the biomedicine and bioanalysis area. Cellulose derivatives-based composites with improved properties were researched as films and membranes for osseointegration, hemodialysis and biosensors, smart textile fibers, tissue engineering scaffolds, hydrogels and nanoparticles for drug delivery. The different preparation strategies of these polymeric composites as well as the most recent available experimental results were described in this review. General aspects such as structure and properties of cellulose extracted from plants or bacterial sources, types of cellulose derivatives and their synthesis methods were also discussed. Finally, the future perspectives related to composites based on cellulose derivatives were highlighted and some conclusions regarding the reviewed applications were drawn.

Controlling the growth of nanosized titania via polymer gelation for photocatalytic applications

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).

Recent Developments in Carriers and Non-Aqueous Solvents for Enzyme Immobilization

Immobilization techniques are generally based on reusing enzymes in industrial applications to reduce costs and improve enzyme properties. These techniques have been developing for decades, and many methods for immobilizing enzymes have been designed. To find a better immobilization method, it is necessary to review the recently developed methods and have a clear overview of the advantages and limitations of each method. This review introduces the recently reported immobilization methods and discusses the improvements in enzyme properties by different methods. Among the techniques to improve enzyme properties, metal–organic frameworks, which have diverse structures, abundant organic ligands and metal nodes, offer a promising platform.

Naturally-derived biopolymers: Potential platforms for enzyme immobilization

Naturally-derived biopolymers such as alginate, chitosan, cellulose, agarose, guar gum/guaran, agar, carrageenan, gelatin, dextran, xanthan, and pectins, etc. have appealed significant attention over the past several years owing to their natural abundance and availability all over the years, around the globe. In addition, their versatile properties such as non-toxicity, biocompatibility, biodegradability, flexibility, renewability, and the availability of numerous reactive sites offer significant functionalities with multipurpose applications. At present, intensive research efforts have been focused on engineering enzymes using natural biopolymers as novel support/composite materials for diverse applications in biomedical, environmental, pharmaceutical, food and biofuel/energy sectors. Immobilization appears as a straightforward and promising approach to developing biocatalysts with improved catalytic properties as compared to their free counterparts. Biopolymers-assisted enzymes are more stable, robust, and recoverable than that of free forms, and can be employed for continuous biocatalytic reactions. The present review highlights the recent developments and use of biopolymers and their advanced composites as support carriers for the immobilization of a variety of different enzymes to develop biocatalysts with desired catalytic activity and stability characteristics for emerging applications.

Spectroscopic and mechanistic analysis of the interaction between Jack bean urease and polypseudorotaxane fabricated with bis-thiolated poly(ethylene glycol) and α-cyclodextrin

Self-assembled polypseudorotaxanes (PPRXs) fabricated with α-cyclodextrin and poly(ethylene glycol) (PEG) or its thiolated derivatives were candidate functional materials for enzyme soft-immobilization, encapsulation and controlled-release. The study of their interaction with Jack bean urease (JBU) indicated that they inconspicuously influenced the activity and stability of JBU during long storage, up to 30 days. The macro-species were inaccessible to JBU's active site and the steric effect might play a significant role in the stabilization of JBU, when compared with the small-molecular sulfhydryl inhibitor thioglycolic acid. Circular dichroism and fluorescence spectra analyses revealed that thiolated PEG₄₀₀-(SH)₂ and its assembly PPRX₄₀₀(SH) brought in perturbations to certain α-helical or β-sheet domains of JBU, making JBU's conformation more flexible. The resulting partial unfolding of domains exposed several hydrophobic clusters and varied JBU's surface hydrophobicity. It also rendered the chromophores more hydrophilic and more bared to the polar environment, leading to the typical bathochromic-shift and quenching in intrinsic and synchronous fluorescence spectra. Moreover, the surface hydrophobicity profile of JBU was depicted by fluorescent probe monitoring and the unique "hydrophobic cave" motif was proposed by analyzing JBU's structural data from the Protein Data Bank. It should be pointed out that conformational variations mainly occurred at the surface region of JBU, while the buried active bi-nickel center was not markedly influenced by the macro-species. The results demonstrated that the PPRXs might act as a proper carrier for JBU encapsulation or soft-immobilization.

Developing potential Helicobacter pylori urease inhibitors from novel oxoindoline derivatives: Synthesis, biological evaluation and in silico study

By recruiting the important moiety from Shikonin, a series of novel oxoindoline derivatives S1-S20 have been synthesized for inhibiting H. pylori urease. The most potent compound S18 displayed better activity (IC₅₀ = 0.71 μM; MIC = 0.48 μM) than the positive controls AHA (IC₅₀ = 17.2 μM) and Metronidazole (MIC = 31.3 μM). With low cytotoxicity, it showed considerable potential for further development. Docking simulation revealed the possible binding pattern of this series. 3D QSAR model was built to discuss SAR and give useful hints for future modification.