Tunable Properties via Composition Modulations of Poly(vinyl alcohol)/Xanthan Gum/Oxalic Acid Hydrogels

Preserving plum perfection: Buckwheat starch edible coating with xanthan gum and lemongrass essential oil

The research focused on the fabrication of composite coatings using buckwheat starch (BS) and xanthan gum (XG) with incorporation of lemongrass (Cymbopogon citratus) essential oil (LEO) with varying concentration (0.75 %, 1.0 % and 1.25 % (w/v). BS was extracted from buckwheat groats (Fagopyrum esculentum) and its physico-chemical characteristics were determined. BS showed spherical and polygonal morphology and its XRD pattern was similar to starch extracted from other cereal sources. The amount of reducing sugar, starch and amylose content in extracted BS were 0.99 ± 0.33 %, 86.32 ± 0.22 % and 21.02 ± 1.89 % respectively, which indicates that BS is a suitable base material for the formation of edible coatings. XG was mixed with BS in different ratios (1:1, 2:1, 3:1 and 4:1) to optimize the best ratio of combination for composite coatings. The coating with a ratio of 2:1 was very smooth and was chosen for incorporation of LEO and the coatings physical, functional, mechanical, thermal and micro-structural characteristics were examined. The coating S5 with 1.25 % (w/v) concentration of LEO showed the best results with least moisture content (MC), minimum water vapor permeability (WVP) and maximum contact angle value. Moreover, the S5 formulation had the highest antioxidant (73.3 %) ability and maximum antimicrobial efficiency with inhibition zones of 22.09 ± 0.06 mm and 28.65 ± 0.14 mm against S. aureus and E. coli respectively. The coatings were then coated on plum fruit, and various parameters like weight loss, pH, shrinkage and TSS were calculated every 4th day during the 20 days of refrigeration period. The coated plums' ripening pace was delayed by the S5 formulation which improved moisture retention, maintained the plums' TSS value and overall pH. Therefore, composite coatings made up of BS, XG and 1.25 % (w/v) can be used as a cost-effective bio-active coating material for plum preservation under refrigeration conditions.

A comprehensive review of recent advances in the applications and biosynthesis of oxalic acid from bio-derived substrates

Organic acids are important compounds with numerous applications in different industries. This work presents a comprehensive review of the biological synthesis of oxalic acid, an important organic acid with many industrial applications. Due to its important applications in pharmaceuticals, textiles, metal recovery, and chemical and metallurgical industries, the global demand for oxalic acid has increased. As a result, there is an increasing need to develop more environmentally friendly and economically attractive alternatives to chemical synthesis methods, which has led to an increased focus on microbial fermentation processes. This review discusses the specific strategies for microbial production of oxalic acid, focusing on the benefits of using bio-derived substrates to improve the economics of the process and promote a circular economy in comparison with chemical synthesis. This review provides a comprehensive analysis of the various fermentation methods, fermenting microorganisms, and the biochemistry of oxalic acid production. It also highlights key sustainability challenges and considerations related to oxalic acid biosynthesis, providing important direction for further research. By providing and critically analyzing the most recent information in the literature, this review serves as a comprehensive resource for understanding the biosynthesis of oxalic acid, addressing critical research gaps, and future advances in the field.

Antimicrobial Activity of Artemisia dracunculus Oil-Loaded Agarose/Poly(Vinyl Alcohol) Hydrogel for Bio-Applications

In this study, the potential use of Artemisia dracunculus essential oil in bio-applications was investigated. Firstly, the phytochemicals from Artemisia dracunculus were analyzed by different methods. Secondly, the Artemisia dracunculus essential oil was incorporated into the hydrogel matrix based on poly(vinyl alcohol) (PVA) and agar (A). The structural, morphological, and physical properties of the hydrogel matrix loaded with different amounts of Artemisia dracunculus essential oil were thoroughly investigated. FTIR analysis revealed the successful loading of the essential oil Artemisia dracunculus into the PVA/A hydrogel matrix. The influence of the mechanical properties and antimicrobial activity of the PVA/A hydrogel matrix loaded with different amounts of Artemisia dracunculus was also assessed. The antimicrobial activity of Artemisia dracunculus (EO Artemisia dracunculus) essential oil was tested using the disk diffusion method and the time-kill assay method after entrapment in the PVA/A hydrogel matrices. The results showed that PVA/agar-based hydrogels loaded with EO Artemisia dracunculus exhibited significant antimicrobial activity (log reduction ratio in the range of 85.5111-100%) against nine pathogenic isolates, both Gram-positive (S. aureus, MRSA, E. faecalis, L. monocytogenes) and Gram-negative (E. coli, K. pneumoniae, S. enteritidis, S. typhimurium, and A. salmonicida). The resulted biocompatible polymers proved to have enhanced properties when functionalized with the essential oil of Artemisia dracunculus, offering opportunities and possibilities for novel applications.

Evaluation of Poly(vinyl alcohol)-Xanthan Gum Hydrogels Loaded with Neomycin Sulfate as Systems for Drug Delivery

In recent years, multidrug-resistant bacteria have developed the ability to resist multiple antibiotics, limiting the available options for effective treatment. Raising awareness and providing education on the appropriate use of antibiotics, as well as improving infection control measures in healthcare facilities, are crucial steps to address the healthcare crisis. Further, innovative approaches must be adopted to develop novel drug delivery systems using polymeric matrices as carriers and support to efficiently combat such multidrug-resistant bacteria and thus promote wound healing. In this context, the current work describes the use of two biocompatible and non-toxic polymers, poly(vinyl alcohol) (PVA) and xanthan gum (XG), to achieve hydrogel networks through cross-linking by oxalic acid following the freezing/thawing procedure. PVA/XG-80/20 hydrogels were loaded with different quantities of neomycin sulfate to create promising low-class topical antibacterial formulations with enhanced antimicrobial effects. The inclusion of neomycin sulfate in the hydrogels is intended to impart them with powerful antimicrobial properties, thereby facilitating the development of exceptionally efficient topical antibacterial formulations. Thus, incorporating higher quantities of neomycin sulfate in the PVA/XG-80/20-2 and PVA/XG-80/20-3 formulations yielded promising cycling characteristics. These formulations exhibited outstanding removal efficiency, exceeding 80% even after five cycles, indicating remarkable and consistent adsorption performance with repeated use. Furthermore, both PVA/XG-80/20-2 and PVA/XG-80/20-3 formulations outperformed the drug-free sample, PVA/XG-80/20, demonstrating a significant enhancement in maximum compressive stress.

pH-Sensitive Degradable Oxalic Acid Crosslinked Hyperbranched Polyglycerol Hydrogel for Controlled Drug Release

pH-sensitive degradable hydrogels are smart materials that can cleave covalent bonds upon pH variation, leading to their degradation. Their development led to many applications for drug delivery, where drugs can be released in a pH-dependent manner. Crosslinking hyperbranched polyglycerol (HPG), a biocompatible building block bearing high end-group functionality, using oxalic acid (OA), a diacid that can be synthesized from CO2 and form highly activated ester bonds, can generate this type of smart hydrogel. Aiming to understand the process of developing this novel material and its drug release for oral administration, its formation was studied by varying reactant stoichiometry, concentration and cure procedure and temperature; it was characterized regarding gel percent (%gel), swelling degree (%S), FTIR and thermal behavior; impregnated using ibuprofen, as a model drug, and a release study was carried out at pH 2 and 7. Hydrogel formation was evidenced by its insolubility, FTIR spectra and an increase in Td and Tg; a pre-cure step was shown to be crucial for its formation and an increase in the concentration of the reactants led to higher %gel and lower %S. The impregnation resulted in a matrix-encapsulated system; and the ibuprofen release was negligible at pH 2 but completed at pH 7 due to the hydrolysis of the matrix. A pH-sensitive degradable HPG-OA hydrogel was obtained and it can largely be beneficial in controlled drug release applications.

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G') was significantly greater than the viscous modulus (G″) for the entire frequency range.

Evaluation of the Antibacterial Properties of Polyvinyl Alcohol-Pullulan Scaffolds Loaded with Nepeta racemosa Lam. Essential Oil and Perspectives for Possible Applications

Essential oil of Nepeta racemosa Lam. was extracted and characterized to determine its antimicrobial activity and potential use in applications. The essential oil was loaded on polyvinyl alcohol-pullulan films and gels and characterized by optical microscopy, scanning electron microscopy, and UV-Vis spectroscopy before having its antimicrobial capacities assessed. The essential oil extracted from Nepeta racemosa Lam. was characterized using gas chromatography coupled with mass spectroscopy, which indicated that the most abundant component was nepetalic acid (55.5%), followed by eucalyptol (10.7%) and other compounds with concentrations of about 5% or less. The essential oil, as well as the loaded films and gels, exhibited good antibacterial activity on both gram-positive and gram-negative strains, with growth inhibition zones larger in some cases than for gentamicin, indicating excellent premises for using these essential-oil-loaded materials for applications in the food industry or biomedicine.

Polyvinyl alcohol/xanthan gum composite film with excellent food packaging, storage and biodegradation capability as potential environmentally-friendly alternative to commercial plastic bag

Polyvinyl alcohol (PVA)-xanthan gum (XG) composite films with good degradation properties were prepared by casting method. The effects of XG amount on thickness, moisture content, water solubility, water vapor transmission (WVP), transmittance and mechanical properties of the composite film were investigated. All composite films produced uniform and transparent films and Fourier transform infrared (FT-IR) spectroscopy, as well as X-ray diffraction (XRD) had proven the formation of hydrogen bonds and subsequently compatibility of the two polymers. In general, addition of XG in PVA was able to decrease moisture content, water solubility and WVP more than the pure PVA films, with sample PX30 demonstrated the best performance. This sample also had the best mechanical properties. It also demonstrated food packaging and capability better than that of commercial plastic bag. More importantly, our sample can be fully decomposed in soil and water within 12 h, which was not only significantly shorter than commercial plastic bag, but also other biodegradable materials. Therefore, PVA/XG-based food packaging material has demonstrated huge potential to be commercialized and replaces commercial plastic bag as an alternative packing material which is renewable, sustainable and environmentally friendly.