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.

Resorbable membrane design: In vitro characterization of silver doped-hydroxyapatite-reinforced XG/PEI semi-IPN composite

In this study, the production and characterization of silver-doped hydroxyapatite (AgHA) reinforced Xanthan gum (XG) and Polyethyleneimine (PEI) reinforced semi-interpenetrating polymer network (IPN) biocomposite, known to be used as bone cover material for therapeutic purposes in bone tissue, were performed. XG/PEI IPN films containing 2AgHA nanoparticles were produced by simultaneous condensation and ionic gelation. Characteristics of 2AgHA-XG/PEI nanocomposite film were evaluated by structural, morphological (SEM, XRD, FT-IR, TGA, TM, and Raman) and biological activity analysis (degradation, MTT, genotoxicity, and antimicrobial activity) techniques. In the physicochemical characterization, it was determined that 2AgHA nanoparticles were homogeneously dispersed in the XG/PEI-IPN membrane at high concentration and the thermal and mechanical stability of the formed film were high. The nanocomposites showed high antibacterial activity against Acinetobacter Baumannii (A.Baumannii), Staphylococcus aureus (S.aureus), and Streptococcus mutans (S.mutans). L929 exhibited good biocompatibility for fibroblast cells and was determined to support the formation of MCC cells. It was shown that a resorbable 2AgHA-XG/PEI composite material was obtained with a high degradation rate and 64% loss of mass at the end of the 7th day. Physico-chemically developed biocompatible and biodegradable XG-2AgHA/PEI nanocomposite semi-IPN films possessed an important potential for the treatment of defects in bone tissue as an easily applicable bone cover. Besides, it was noted that 2AgHA-XG/PEI biocomposite could increase cell viability, especially in dental-bone treatments for coating, filling, and occlusion.

Prospects of Biogenic Xanthan and Gellan in Removal of Heavy Metals from Contaminated Waters

Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, including two commercially available heteropolysaccharides-xanthan and gellan. As biodegradable and non-toxic fermentation products, xanthan and gellan have been successfully tested in various remediation techniques. Here, to highlight their prospects as green adsorbents for water decontamination, we have reviewed their biosynthesis machinery and chemical properties that are linked to their sorptive interactions, as well as their actual performance in the remediation of heavy metal contaminated waters. Their sorptive performance in native and modified forms is promising; thus, both xanthan and gellan are emerging as new green-based materials for the cost-effective and efficient remediation of heavy metal-contaminated waters.

Zwitterionic polymer modified xanthan gum with collagen II-binding capability for lubrication improvement and ROS scavenging

High friction of damaged cartilage requires long-acting lubricated additive, which can also effectively scavenge reactive oxidative species (ROS) produced by mechanically stimulated chondrocytes. In this study, xanthan gum (XG) was grafted by poly (sulfobetaine methacrylate) (PSBMA) (the [XG]/[SBMA] molar ratio is 1:5 or 1:10), forming nanoparticles and then conjugated with collagen II-binding peptide, finally obtaining CBPXGSB1/5 or CBPXGSB1/10. Therein, the CBPXGSB1/5 was chosen as optimal lubricated additive. The results show that hydrated effect of PSBMA side chains endows CBPXGSB1/5 with favorable lubrication property (COF is 0.063). Furthermore, the CBPXGSB1/5 combining lubrication property and specific binding capability together may achieve the long-acting lubrication for injured cartilage in medical field. The CBPXGSB1/5 also possesses antioxidation verified by DPPH assay and exhibits synergistically enhanced ROS (OH, O₂^- and H₂O₂) scavenging. Besides, cytotoxicity experiment demonstrates that CBPXGSB1/5 has good biocompatibility. Therefore, multifunctional CBPXGSB1/5 developed here may have promising application potential in osteoarthritis treatment.

Stable Hydrogel Electrolytes for Flexible and Submarine-Use Zn-Ion Batteries

Due to their intrinsic safety, low cost, and eco-friendliness, aqueous Zn-ion batteries (ZIBs) have shown significant potential for wearable and flexible electronic devices. However, the lack of a stable and durable electrolyte for flexible ZIBs greatly hampers their applications in harsh conditions during daily use. In this work, we reported a stable hydrogel electrolyte, fabricated by coupling the grafted copolymer xanthan gum-polyacrylamide (XG-PAM) with cotton cellulose nanofiber (CNF), denoted XG-PAM/CNF. The designed XG-PAM/CNF hydrogel electrolyte exhibited high ionic conductivity (28.8 mS cm^-1), good adhesion, high mechanical strength, and strong ion adsorption. In addition, it also shows an inhibition effect on the generation of dendrites. The flexible ZIBs with the XG-PAM/CNF hydrogel electrolyte achieved high specific capacity (237 mA·h g^-1) and excellent cycling stability (86.2% retention over 1000 cycles at 4 C). Notably, flexible ZIBs withstand severe conditions, such as bending, folding, poking, washing, soaking, and underwater usage. Furthermore, an underwater warning rescue system application was proposed. Consequently, this work provides a new approach and application for the development of reliable and durable wearable energy storage devices.

Dendritic star polymer of polyacrylamide based on a β-cyclodextrin trimer: a flocculant and drug vehicle

3-β-CD-PAM: a better flocculant in water treatment and methylene blue dye removal, and a vehicle for the drugs diclofenac sodium and doxorubicin.

Studies on Electrical, Thermal and Corrosion Behaviour of Cashew Tree Gum Grafted Poly(Acrylamide)

The present work aimed to study the thermal transitions, electrical properties and corrosion behaviour of cashew tree gum (CTG), poly (acrylamide) (PAM) and cashew tree gum grafted poly (acrylamide) (CTG-g-PAM) copolymer. Various amounts of acrylamide monomer were grafted onto cashew gum using a radical polymerization method. The formation of graft copolymer was analysed by FTIR, UV, SEM, DSC and electrical conductivity measurements. The FTIR and UV spectrum infers the occurrence of strong intermolecular interaction between cashew gum and poly (acrylamide). SEM photographs revealed that the acrylamide unit was well inserted into the cashew gum segments. The DSC analysis showed a significant decrease in glass transition temperature with an increase in amount of acrylamide chains. CTG shows higher AC conductivity than PAM and the conductivity of graft copolymer increases with the concentration of acrylamide up to certain concentration of monomer and thereafter the value decreases. The dielectric properties such as dielectric constant and dielectric loss tangent values of PAM was lower than CTG and the dielectric values also shows a similar trend as AC conductivity. CTG, PAM and its graft copolymer with various amount of poly (acrylamide) have been investigated as a corrosion inhibition for mild steel in hydrochloric acid. The inhibition efficiency increased with increase in concentration of PAM in the graft copolymer. PAM was found to have the high inhibition efficiency than CTG, due to the difference in their molecular structures. The corrosion rate of all the samples enhanced with the raise in temperature whereas the inhibition efficiency deceases.

Microbial metabolism induced chain shortening of polyacrylamide with assistance of bioelectricity generation

The water-soluble polyacrylamide (PAM) can accumulate in ecosystems and cause serious environmental pollution. Biological approach achieves poor PAM degradation efficiency, due to the extreme resistance of PAM to the microbial metabolism. In the present work, the potential of bioelectrochemical system (BES) as an effective tool to degrade the PAM is adequately evaluated. The closed-circuit operation of BES obtains COD removal efficiencies of 29.2 and 33.6 % for the PAM and polyacrylic acid (PAA), respectively. In comparison, 4.3 and 2.7 % of COD are removed after the PAM and PAA are treated in the open-circuit BES, and 7.3 and 6.6 % are removed in the aerobic BES. These results suggest the bioelectricity generation is crucial to trigger the activity of bioanode for the effective degradation of PAM. Bioelectricity generation not only favors the decomposition of carbon backbone but also facilitates the hydrolysis of amide group in the side-chain of PAM. Microbial attack on the carbon backbone of PAM is proposed to initiate at the head-to-head linkage, resulting in the formation of ether bond within the shortened carbon chain. The Ignavibacterium sp. and phenotypically uncharacterized bacteria are classified as the dominant species on the anode of PAM-fed BES.

Evaluation of a matrix tablet prepared with polyacrylamide-g-sodium alginate co-polymers and their partially hydrolyzed co-polymers for sustained release of diltiazem hydrochloride

Diltiazem hydrochloride (DTZ) matrix tablets were prepared using polyacrylamide-grafted sodium alginate (PAam-g-SA) co-polymers having different percentages of grafting and their partially hydrolyzed products with a view to achieve sustained release of the highly water-soluble drug. PAam-g-SA co-polymers having different percentages of grafting were synthesized by free radical polymerization using acrylamide (Aam) as monomer and ammonium persulphate (APS) as initiator, and the resulting co-polymers were subjected to alkaline hydrolysis to produce their corresponding partially hydrolyzed co-polymers. Matrix tablets of DTZ were prepared by wet granulation using either PAam-g-SA co-polymers or partially hydrolyzed PAam-g-SA co-polymers. The effect of percentage grafting, drug load and calcium gluconate (CG), used as excipient, was studied in simulated gastrointestinal fluid. While the tablets prepared using the co-polymer having higher percentages of grafting provided faster drug release (100% in 5.5 h), the tablets prepared with the corresponding hydrolyzed co-polymer released the drug slowly (71% in 12 h). This behaviour in release appeared to be controlled by the relative magnitude of the viscosity and the swelling capacity of the copolymers. Moreover, increase in drug load tended to decrease the drug release from all types of tablets and increase in the amount of CG increased the drug release. FT-IR and DSC studies revealed the absence of any interaction between the drug and the co-polymers. The matrix tablet made of partially hydrolyzed graft co-polymer having the highest percentage of grafting provided the most sustained release of the drug.

High-technology materials based on modified polysaccharides

Polysaccharides are abundantly available from farm, forest, and microbial resources. They are used in myriad applications. It has been established in the authors' laboratory that their performance is enhanced considerably on purification, grafting by polyacrylamide (PAM), and subsequent hydrolysis as well as cationization. The most significant performance is enhanced in flocculation where it has been found that the modified polysaccharides outperform existing flocculants in national and international markets. Similar effects are observed in their performance in turbulent drag reduction (DR), percolation, and rheology. The present article outlines the details of materials, mechanisms, and practical applications of these novel materials.

Evaluation and Controlled Release Characteristics of Modified Xanthan Films for Transdermal Delivery of Atenolol

The present study was performed to evaluate the possibility of using modified xanthan films as a matrix system for transdermal delivery of atenolol (ATL), which is an antihypertensive drug. Acrylamide was grafted onto xanthan gum (XG) by free radical polymerization using ceric ion as an initiator. Fourier transform infrared spectroscopy and differential scanning calorimetry indicated the formation of the graft copolymer. The obtained graft copolymer was loaded with ATL and films were fabricated by solution casting method for transdermal application. Various formulations were prepared by varying the grafting ratio, drug loading, and different penetration enhancers. The formulations prepared were characterized for weight, thickness uniformity, water vapor transmission rate, and uniformity in drug content of the matrix. All the thin films were slightly opaque, smooth, flexible, and permeable to water vapor, indicating their permeability characteristics suitable for transdermal studies. Fourier transform infrared spectroscopy and differential scanning calorimetry studies indicated no significant interactions between drug and polymer. Drug is distributed uniformly in the matrix but showed a slight amorphous nature. Drug-loaded films were analyzed by X-ray diffraction to understand the drug polymorphism inside the films. Scanning electron microscopic studies of the placebo and drug-loaded films demonstrated a remarkable change in their surface morphology. The skin irritation tests were performed in mice and these results suggested that both placebo and drug-loaded films produced negligible erythema and edema compared to formalin (0.8% v/v) as the standard irritant. The in vitro drug release studies were performed in phosphate buffer saline using a Keshary-Chien diffusion cell. Different formulations were prepared and variations in drug release profiles were observed. Release data were analyzed by using the Ritger and Peppas equation to understand the mechanism of drug release as well as the estimation of n values, which ranged between 0.41 and 0.53, suggesting a Fickian diffusion trend.