The synthesis and characterization of a xanthan gum-acrylamide-trimethylolpropane triglycidyl ether hydrogel

Rational modification of xanthan gum based on assistance of molecular dynamics simulation

Graft copolymerization is an effective approach to improve performance of polysaccharide. However, selecting the most suitable modification strategy can be challenging due to the intricate molecular structure. Rational design through computer aided molecular dynamics (MD) simulations requires substantial computational resources. This study designed a simplified MD simulation strategy and suggested that grafting acrylamide (AM) could effectively adjust the molecular conformation of xanthan gum (XG) and its derivatives, thus regulating its viscosity and gelation properties. To rationally modify XG, a uniform experimental design was applied to tune the grafting ratios ranging from 72 % to 360 %, resulting in XG-AM solutions with viscosity ranging from 9 to 104 mPa•s at a concentration of 0.3 %. XG-AM was crosslinked by acid phenolic resin to generate gel with the viscosity of 7890 mPa·s in 3 days, which was 13 times the viscosity of unmodified XG. The controllable gelation will enhance the efficacy of XG-AM in oil recovery. By integrating rational selection of grafting strategies based on simplified MD simulation of polysaccharide derivatives and controllable grafting modification with specified grafting rates, customized production of polysaccharide derivatives can meet the requirements of a diverse range of applications.

Synthesis of Poly(GG-co-AAm-co-MAA), a Terpolymer Hydrogel for the Removal of Methyl Violet and Fuchsin Basic Dyes from Aqueous Solution

A novel adsorbent designated as terpolymer hydrogel (gellan gum-co-acrylamide-co-methacrylic acid) was prepared by free radical polymerization of gellan gum (GG), methacrylic acid (MAA), and acrylamide (AAm) using N,N-methylene bis-acrylamide (MBA) as cross-linker and ammonium per sulfate (APS) as the initiator of the reaction. The synthesized gel was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA) and was used for the adsorptive removal of methyl violet (MV) and Fuchsin Basic (FB) dyes from aqueous solution. The effect of temperature, contact time, pH, and concentration on them under the study adsorption process was evaluated. Freundlich isotherm and pseudo-second-order kinetic models were found to be best in fitting the isothermal and kinetics data. The water diffusion and % swelling of hydrogel were studied at various pH in distilled water and at neutral pH in tap water. The diffusion was found to be of Fickian type with a maximum swelling of 5132%. The maximum adsorption capacity was 233 mg/g against MV and 200 mg/g against FB dyes. The swelling and adsorption were pH dependent and increased with increase in pH. The enthalpy, Gibbs free energy, and entropy changes of adsorption for both the dyes indicated the adsorption process to be exothermic, feasible, and spontaneous. The hydrogel was successfully regenerated using acetone and distilled water for five cycles and still, its dye removal efficiency was 80% of its original value. The poly(GG-co-AAm-co-MAA) hydrogel successfully removed the selected dyes from water and could thus be used as an efficient alternative sorbent for cationic dye removal from aqueous solutions.

A novel ZIF-8@IL-MXene/poly (N-isopropylacrylamide) nanocomposite hydrogel toward multifunctional adsorption

Phenols, dyes, and metal ions present in industrial wastewater can adversely affect the environment and leach biological carcinogens. Given that the current research focuses only on the removal of one or two of those categories. Herein, this work reports a novel ZIF-8@IL-MXene/Poly(N-isopropylacrylamide) (NIPAM) nanocomposite hydrogel that can efficiently and conveniently absorb and separate multiple pollutants from industrial wastewater. Ionic liquid (IL) was grafted onto MXene surfaces using a one-step method, and then incorporated into NIPAM monomer solutions to obtain the IL-MXene/PNIPAM composite hydrogel via in-situ polymerization. ZIF-8@IL-MXene/PNIPAM nanocomposite hydrogels were obtained by in-situ growth of ZIF-8 on the pore walls of composite hydrogels. As-prepared nanocomposite hydrogel showed excellent mechanical properties and can withstand ten repeated compressions without any damage, the specific surface area increased by 100 times, and the maximum adsorption capacities for p-nitrophenol (4-NP), crystal violet (CV), and copper ion (Cu2+) were 198.40, 325.03, and 285.65 mg g-1, respectively, at room temperature. The VPTTs of all hydrogels ranged from 33 to 35 °C, so the desorption process can be achieved in deionized water at 35-40 °C, and its adsorption capacities after five adsorption-desorption cycles decreased to 79%, 91%, and 29% for 4-NP, CV, and Cu2+, respectively. The adsorption data fitting results follow pseudo-second-order kinetics and Freundlich models, which is based on multiple interactions between the functional groups contained in hydrogels and adsorbent molecules. The hydrogel is the first to realize the high-efficiency adsorption of phenols, dyes and metal ions in industrial wastewater simultaneously, and the preparation process of hydrogels is environmentally friendly. Also, giving hydrogel multifunctional adsorption is beneficial to promote the development of multifunctional adsorption materials.

Magnetic xanthan gum-silk fibroin hydrogel: A nanocomposite for biological and hyperthermia applications

A magnetic xanthan hydrogel/silk fibroin nanobiocomposite (XG hydrogel/SF/Fe3O4) was designed, fabricated, and characterized using analyzing methods such as FT-IR, EDX, FE-SEM, XRD, TGA, and VSM to evaluate the exact structure of product nanobiocomposite. The FE-SEM images reveal the presence of spherical shapes exhibiting a narrow size range and homogeneous distribution, measuring between 30 and 35 nm in diameter. The VSM analysis demonstrates the superparamagnetic properties of the XG hydrogel/SF/Fe3O4 nanobiocomposite, exhibiting a magnetic saturation of 54 emu/g at room temperature. The biological response of the nanobiocomposite scaffolds was assessed through cell viability and red blood cell hemolytic assays. MCF10A cells were exposed to a concentration of 1.75 mg/mL of the nanobiocomposite, and after 2 and 3 days, the cell viability was found to be 96.95 % and 97.02 %, respectively. The hemolytic effect was nearly 0 % even at higher concentrations (2 mg/mL). Furthermore, the magnetic nanobiocomposite showed excellent potential for hyperthermia applications, with a maximum specific absorption rate of 7 W/g for 1 mg/mL of the sample under a magnetic field in different frequencies (100, 200, 300, and 400 MHz) and 5 to 20 min time intervals.

Novel tetrahydrocurcumin integrated mucoadhesive nanocomposite κ-carrageenan/xanthan gum sponges: a strategy for effective local treatment of oral cancerous and precancerous lesions

Oral cancer is one of the leading causes of death worldwide. Oral precancerous lesions (OPL) are the precursors of oral cancer, with varying degrees of progression. Tetrahydrocurcumin (THC) is a major metabolite of curcumin with superior anticancer properties against various types of cancer. However, THC's clinical outcome is limited by its poor aqueous solubility. Herein, we developed novel mucoadhesive biopolymer-based composite sponges for buccal delivery of THC, exploiting nanotechnology and mucoadhesion for efficient prevention and treatment of oral cancer. Firstly, THC-nanocrystals (THC-NC) were formulated and characterized for subsequent loading into mucoadhesive composite sponges. The anticancer activity of THC-NC was assessed on a human tongue squamous carcinoma cell line (SCC-4). Finally, the chemopreventive activity of THC-NC loaded sponges (THC-NC-S) was examined in DMBA-induced hamster OPL. The selected THC-NC exhibited a particle size of 532.68 ± 13.20 nm and a zeta potential of -46.08 ± 1.12 mV. Moreover, THC-NC enhanced the anticancer effect against SCC-4 with an IC50 value of 80 µg/mL. THC-NC-S exhibited good mucoadhesion properties (0.24 ± 0.02 N) with sustained drug release, where 90% of THC was released over 4 days. Furthermore, THC-NC-S had a magnificent potential for maintaining high chemopreventive activity, as demonstrated by significant regression in the dysplasia degree and a decline in cyclin D1 (control: 40.4 ± 12.5, THC-NC-S: 12.07 ± 5.2), culminating in significant amelioration after 25 days of treatment. Conclusively, novel THC-NC-S represent a promising platform for local therapy of OPL, preventing their malignant transformation into cancer.

Ultrastable Emulsion Stabilized by the Konjac Glucomannan-Xanthan Gum Complex

Surfactant-free emulsions are currently gaining increased interest due to their technofunctional, health-promoting, economic, biocompatible, and sustainable characteristics. Herein, we report an ultrastable, surfactant-free emulsion stabilized by the konjac glucomannan (KGM)-xanthan gum (XG) complex. The results suggested that KGM-XG tended to adsorb onto the oil/water interface, causing a reduction in interfacial tension. The emulsion droplets were less than 1 μm in diameter and had a narrow size distribution. Using laser confocal microscopy and cryo-SEM, it was observed that KGM-XG generated a compact film on the surface of emulsion droplets while simultaneously constructing a three-dimensional network in the continuous phase. Both of these factors contributed to the stability of the emulsion. The present study presents a straightforward approach for producing highly stable emulsions stabilized by polysaccharides. These emulsions can be effectively utilized to enhance the water resistance of cellulose paper, which is extensively employed in the packaging industry.

Ice-Templated and Cross-Linked Xanthan-Based Hydrogels: Towards Tailor-Made Properties

The use of polysaccharides with good film-forming properties in food packaging systems is a promising area of research. Xanthan gum (XG), an extracellular polysaccharide, has many industrial uses, including as a common food additive (E415). It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. Nevertheless, XG-based polymer films have some disadvantages, such as poor mechanical properties and high hydrophilic features, which reduce their stability when exposed to moisture and create difficulties in processing and handling. Thus, the objective of this work was to stabilize a XG matrix by cross-linking it with glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, or epichlorohydrin below the freezing point of the reaction mixture. Cryogelation is an ecological, friendly, and versatile method of preparing biomaterials with improved physicochemical properties. Using this technique, XG-based cryogels were successfully prepared in the form of microspheres, monoliths, and films. The XG-based cryogels were characterized by FTIR, SEM, AFM, swelling kinetics, and compressive tests. A heterogeneous morphology with interconnected pores, with an average pore size depending on both the nature of the cross-linker and the cross-linking ratio, was found. The use of a larger amount of cross-linker led to both a much more compact structure of the pore walls and to a significant decrease in the average pore size. The uniaxial compression tests indicated that the XG-based cryogels cross-linked with 1,4-butanediol diglycidyl ether exhibited the best elasticity, sustaining maximum deformations of 97.67%, 90.10%, and 81.80%, respectively.

Preparation and emulsification properties of cationic starch-xanthan gum composite nanoparticles

In this work, nanoparticles were prepared by the composite of cationic starch (CS) and xanthan gum (XG) through gelatinization and alcohol precipitation for the first time. Physicochemical properties, micromorphology, and emulsification properties of CS/XG nanoparticles were measured. SEM showed that after compositing with XG, the diameter size of the CS/XG nanoparticles was increased from about 50 nm to 150-300 nm. FT-IR, XRD and ¹³C CP/MAS NMR confirmed that XG was successfully complexed with CS. Besides, the visual observation indicated emulsions stabilized by CS/XG nanoparticles had excellent storage and thermal properties. Additionally, the rheological and stability results of emulsions show that pH and NaCl had effects on the rheological and stability properties of emulsions, which means that the prepared emulsions had environmental responsiveness. Thus, this work provides an efficient method to prepare CS and GX composite nanoparticles with efficient emulsifying properties.

Photo-degradable salecan/xanthan gum ionic gel induced by iron (III) coordination for organic dye decontamination

As dye adsorbents with great potential, polysaccharide-based hydrogels are significantly hampered in practical application owing to intricate preparation methods, low absorption, and bad degradability. Salecan is a water-soluble extracellular polysaccharide with excellent physicochemical and biological properties. Here, salecan and xanthan gum were first used as a dual-precursors system, their mixed solution was crosslinked by Fe³⁺ to assemble a photo-degradable ionic gel for malachite green (MG) adsorption. Photo-degradation was done using visible light under very mild conditions, which gave rise to gel network dissolution and homogeneous solution formation. Extensive dynamic coordinate interactions between Fe³⁺ and polysaccharides maintained gel matrix stability and were systematically investigated. The control of water uptake, micro-structure, and rheology can be facilely implemented by tuning salecan/xanthan gum ratios. Furthermore, various parameters such as polysaccharide ratios, pHs, MG concentrations, and contact time affecting adsorption were optimized using batch experiments. Adsorption process accurately adhered to pseudo-second-order kinetic and Langmuir isotherm model, with the maximum adsorption capacity of 463.0 mg/g. Such mechanism implied monolayer chemisorptive characteristics. The gel exhibited satisfactory reusability and was recycled five times without apparent decrease in adsorption capacity. From these results, the photo-degradable Fe³⁺-induced salecan/xanthan gum ionic gel is an alternative and sustainable absorbent for MG removal.

Methylene blue uptake by gum arabic/acrylic amide/3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt semi-IPN hydrogel

In this study, the capacity of methylene blue (MB) uptake from aqueous solution was investigated using acrylic amide-co-3-Allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt/Gum Arabic semi-IPN hydrogel. The semi-IPN hydrogels were prepared by the classical free radical solution technique. The swelling experiments were carried out gravimetrically and the swelling kinetics parameters were calculated. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) confirmed the semi-IPN hydrogel formation. The MB uptake was studied by the batch technique and the impact of different conditions was investigated. It was found that the obtained semi-IPN hydrogels gave adsorption capacity for the dye within a range of 101-187 mg g^-1 at the initial dye concentration of 100 mg/L. The adsorption kinetics (pseudo-first-order and pseudo-second-order) and the adsorption isotherms (Langmuir, Freundlich, and Temkin equations) were tested and the adsorption data was well described by the pseudo-second-order and Freundlich models, respectively. The maximum adsorption capacity calculated by the Langmuir model (R² = 0.8718) was 655.2 mg g^-1. The thermodynamic study indicated the spontaneity and the endothermic nature of MB adsorption. Furthermore, the usability study showed that the prepared adsorbents could be employed repeatedly for successive 5 cycles of adsorption and desorption.

Semi-continuous production of xanthan in biofilm reactor using Xanthomonas campestris

Semi-continuous production of xanthan gum using self-immobilized Xanthomonas campestris cells in biofilm reactors was studied. Fermentation was carried out using two different designs of biofilm reactor equipped with a) stainless-steel support (SSS) and b) polyethylene support (PES). Fermentation was performed in three cycles with refreshing the media at the beginning of each: cycle 1, 0-27 h; cycle 2, 27-54 h; and cycle 3, 54-78.5 h. Results showed that the glucose consumption and the pH reduction in the PES biofilm reactor was faster compared to the SSS biofilm reactor. Scanning electron microscopy showed that the SSS was capable to immobilize more cells during the growth of X. campestris. The maximum concentration of xanthan gum in the SSS biofilm reactor obtained after 27 h (3.47 ± 0.71 g/L), while the maximum concentration of xanthan in the PES biofilm reactor obtained after 78.5 h (3.21 ± 0.68 g/L). Thermal stability analysis of xanthan using differential scanning calorimetry showed the presence of two fractures attributed to dehydration and degradation of polymer. The thermogram represented both endothermal and exothermal behaviour of xanthan polymer. Furthermore, the functional groups and molecular structure of the xanthan produced in this study was evaluated using Fourier transform infrared spectrometry and also proton nuclear magnetic resonance. in addition, the surface tension of (0.2 %, w/v) xanthan gum solution was in a range of 52.16-56.5 mN/m. Rheological analysis of xanthan showed that the G' values were higher than the G″ in all frequencies demonstrating a relatively high elasticity of the produced xanthan gum.

Modified xanthan gum for methyl orange uptake: Kinetic, isotherm, and thermodynamic behaviors

A novel hydrogel, named XGTTE, was prepared by modification of acrylamide and trimethylolpropane triglycidyl ether (TTE) on xanthan gum (XG). XGTTE was utilized as an adsorbent to remove methyl orange (MO) from an aqueous solution. Functional groups present in the external surface of XGTTE, such as carboxyl, hydroxyl, and amino groups, were identified, and these functional groups are responsible for the occurrence of the mechanism for MO adsorption. The structure of XGTTE after MO adsorption became more disordered. The adsorption dynamics and isotherms of MO onto XGTTE conformed well to the pseudo-second-order kinetics and the Freundlich equation, indicated that the adsorption included physical and chemical adsorption, with electrostatic interaction and hydrogen-bonding interaction. The calculated values of the thermodynamic parameters, such as changes in enthalpy (ΔH) and entropy (ΔS) were 27.30 kJ/mol and 125.63 J/mol/K, respectively. The changes in free energy (ΔG) were - 9.53 kJ/mol (293.15 K), -10.16 kJ/mol (298.15 K), -10.78 kJ/mol (303.15 K), -11.41 kJ/mol (308.15 K), and - 12.04 kJ/mol (313.15 K), respectively, indicating the adsorption process is endothermic, spontaneous, and entropic. The maximum adsorption capacities of XGTTE2, XGTTE3, XGTTE4, XGTTE5, and XGTTE6 for MO were 18.62 ± 0.99, 21.92 ± 0.84, 28.60 ± 0.84, 29.56 ± 0.99, and 12.38 ± 0.84 mg/g, respectively.

Facile synthesis of xanthan biopolymer integrated 3D hierarchical graphene oxide/titanium dioxide composite for adsorptive lead removal in wastewater

Xanthan integrated graphene oxide functionalized by titanium dioxide was successfully prepared through facile, eco-friendly and cost effective ice-templating technique. The three-dimensional (3D) graphene composite demonstrated relatively high temperature stability, chemical functionalities and porous sponge-like structure. The adsorption of lead was favored by high initial concentration and shaking speed at the operational solution pH. The process equilibrium and kinetic adhered to the Langmuir and pseudo-second-order correlations, respectively. The biomass integrated graphene composite showed maximum adsorption capacities ranging from 132.18 to 199.22 mg/g for 30-70 °C. Moreover, it was highly regenerable under mild conditions (0.1 M hydrochloric acid, 30 °C) and used repeatedly while retaining 84.78% of its initial adsorption capacity at the fifth adsorption-regeneration cycle. With comparatively high lead adsorption capacities, adequate recyclability and environmentally friendliness, the as-prepared 3D graphene composite has high application potential in heavy metal-wastewater separation for protection of the environment and human health.

All-solid-state supercapacitors using a highly-conductive neutral gum electrolyte

Recently, the development of safe, stable, and long-life supercapacitors has attracted considerable interest driven by the fast-growth of flexible wearable devices. Herein, we report an MnO2-based symmetric all-solid-state supercapacitor, using a neutral gum electrolyte that was prepared by embedding aqueous sodium sulfate solution in a biopolymer xanthan gum. Resulting from the high ion conductivity 1.12 S m-1, good water retention, and high structure adaption of such gum electrolyte, the presently described supercapacitor showed high electrochemical performance with a specific capacitance of 347 F g-1 at 1 A g-1 and an energy density of 24 μW h cm-2 The flexible supercapacitor possesses excellent reliability and achieves a retaining capacitance of 82% after 5000 cycles. In addition, the as-prepared supercapacitor demonstrated outstanding electrochemical stability at temperatures between -15 °C to 100 °C.

Modified xanthan gum for crystal violet uptake: kinetic, isotherm, and thermodynamic behaviors

Modified xanthan gum (XG-AM-TTE) was employed as an adsorbent to study the adsorption behavior, thermodynamics and kinetics of crystal violet (CV) from an aqueous solution. Fourier transform infrared spectroscopy analysis indicates that the functional groups present in the adsorbent, such as carboxyl, ester and hydroxyl groups, are included on the external surface of the material, and these groups are potential active sites for interaction with CV. According to X-ray diffraction results, the structure of XG-AM-TTE after CV adsorption became more disordered, and the microstructure change is an indication of effective adsorption of CV to the surface, with CV becoming remarkably dispersed in the adsorbent according to the scanning electron microscopy observations. The adsorption kinetics and adsorption equilibrium were best described by the pseudo-second-order model and Freundlich isotherms, respectively. The thermodynamic parameters, as the Gibbs-free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), indicated that the adsorption is a spontaneous, endothermic and entropy increase process. The maximum adsorption capacity of XG-AM-TTE was 183 ± 12 mg/g, suggesting that XG-AM-TTE is an efficient adsorbent.