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Oxidized sodium alginate (OSA) is selected as an appropriate material to be extensively applied in regenerative medicine, 3D-printed/composite scaffolds, and tissue engineering for its excellent physicochemical properties and biodegradability. However, few literatures have systematically investigated the structure and properties of the resultant OSA and the effect of the oxidation degree (OD) of alginate on its biodegradability and gelation ability. Herein, we used NaIO4 as the oxidant to oxidize adjacent hydroxyl groups at the C-2 and C-3 positions on alginate uronic acid monomer to obtain OSA with various ODs. The structure and physicochemical properties of OSA were evaluated by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and thermogravimetric analysis (TGA). At the same time, gel permeation chromatography (GPC) and a rheometer were used to determine the hydrogel-forming ability and biodegradation performance of OSA. The results showed that the two adjacent hydroxyl groups of alginate uronic acid units were successfully oxidized to form the aldehyde groups; as the amount of NaIO4 increased, the OD of OSA gradually increased, the molecular weight decreased, the gelation ability continued to weaken, and degradation performance obviously rose. It is shown that OSA with various ODs could be prepared by regulating the molar ratio of NaIO4 and sodium alginate (SA), which could greatly broaden the application of OSA-based hydrogel in tissue engineering, controlled drug release, 3D printing, and the biomedical field.

3D printing technology has great potential for the reconstruction of human skin. However, the reconstructed skin has some differences from natural skin, largely because the hydrogel used does not have the appropriate biological and physical properties to allow healing and regeneration. This study examines the swelling, degradability, microstructure and biological properties of Collagen/Sodium Alginate (Col/SA) hydrogels of differing compositions for the purposes of skin printing. Increasing the content of sodium alginate causes the hydrogel to exhibit stronger mechanical and swelling properties, a faster degradation ratio, smaller pore size, and less favorable biological properties. An optimal 1% collagen hydrogel was used to print bi-layer skin in which fibroblasts and keratinocytes showed improved spreading and proliferation as compared to other developed formulations. The Col/SA hydrogels presented suitable tunability and properties to be used as a bioink for bioprinting of skin aiming at finding applications as 3D models for wound healing research.

The effects of a new edible sodium alginate (SA) coating incorporating cinnamon essential oil nanocapsules (CEO-NPs) and nisin were investigated with beef slices in refrigerated storage for 15 days. All beef samples were analyzed for physicochemical properties (pH, weight loss, and total volatile base nitrogen) and antimicrobial activity against total bacteria. Changes in color parameters and sensory attributes of all beef samples also were evaluated. Incorporation of the complex of CEO-NPs and nisin into the SA coating retarded the growth of microorganisms and reduced lipid oxidation, as determined by pH, total volatile base nitrogen, and total bacteria counts. This treatment also extended the shelf life of beef slices to 15 days. The SA coating with CEO-NPs and nisin significantly reduced weight loss and improved color, odor, texture, and purge quality of the beef samples. These results suggest that treatment with the SA coating enriched with CEO-NPs and nisin can significantly retard the deterioration of beef slices, and the complex of CEO-NPs and nisin can improve antioxidant, antibacterial, and sensory properties of the SA coating. This new edible coating could be useful for preserving beef slices.

In this work, microalgae-based zinc oxide nanoparticles loaded with electrospun polyvinyl alcohol (PVA)/sodium alginate (SA) nanofibers were fabricated by electro-spinner. PVA/SA fibrous mats were crosslinked by citric acid, which enhanced their thermal stability and swelling behavior. Green-synthesized ZnO NPs were laboratory synthesized and characterized by FTIR, XRD, EDX, SEM, TEM and TGA analyses. Electrospinning of PVA/SA with optimized mixing ratios was further carried out with different ratios of ZnO NPs of (0.25, 0.50 and 0.75%, wt./v) to fabricate SA/PVA/ZnO composite nanofibers. The formula of NF of (SA/PVA/ZnO (0.75%) with different ratios of glycine was used for testing as topical wound dressing as promised biomaterials. Results revealed that NF formula coded AS3.3; composed of (10%PVA/1.5%SA/10%CA/0.75%ZnO/0.5% glycine), in contrast to all the other formulations examined; showed marked reduced percentages of biofilm development of both Gram -positive and Gram -negative bacteria in relation to fungal cells. The relative viable count for Bacillus cereus (98.40 ± 0.51%), Salmonella paratyphi (98.33 ± 0.79%), and Candida albicans (94.29 ± 0.76%) decreased significantly after 36-hour of incubation period with AS3.3 treatment. The obtained findings offered that the prepared composite nanofiber based on ZnO NPs and glycine; could be used as a promising and excellent antimicrobial dressing for inhibiting the microbial growth for the topical wounds healing.

In this study, two different materials—alginate and glutaraldehyde-activated chitosan beads—were used for the co-immobilization of α-amylase, protease, and pectinase. Firstly, optimization of multienzyme immobilization with Na alginate beads was carried out. Optimum Na alginate and CaCl2 concentration were found to be 2.5% and 0.1 M, respectively, and optimal enzyme loading ratio was determined as 2:1:0.02 for pectinase, protease, and α-amylase, respectively. Next, the immobilization of multiple enzymes on glutaraldehyde-activated chitosan beads was optimized (3% chitosan concentration, 0.25% glutaraldehyde with 3 h of activation and 3 h of coupling time). While co-immobilization was successfully performed with both materials, the specific activities of enzymes were found to be higher for the enzymes co-immobilized with glutaraldehyde-activated chitosan beads. In this process, glutaraldehyde was acting as a spacer arm. SEM and FTIR were used for the characterization of activated chitosan beads. Moreover, pectinase and α-amylase enzymes immobilized with chitosan beads were also found to have higher activity than their free forms. Three different enzymes were co-immobilized with these two materials for the first time in this study.

Biodegradable sodium alginate/gum Arabic (SG) films were obtained. The influence of Syzygium cumini seeds extract (SCSE) incorporation in SG films on morphological structure, polymer interaction, thermal behavior, antioxidant activity and physical characteristics were investigated. Moreover, the fabricated films were tested as wrapping materials to extend the shelf life of sunflower oil. Scanning electron microscopy micrographs showed heterogeneous and rough surface after incorporation by SCSE. Possible cross-linked interaction between alginate and gum Arabic and physical interaction between SCSE and SG films were assessed by FT-IR. Although, the addition of SCSE into SG films declined the thermal stability, elongation at break (EB), tensile strength (TS) and moisture content, films with better opacity, solubility and water vapor permeability were obtained. The SG-SCSE films showed obvious obstructing effects on the oil oxidation process during storage days. According to these results, it can be emphasized that edible films with the highest concentrations of added SCSE can serve as a good source of antioxidant compounds and physicochemical properties. Certainly, these properties can be usefully incorporated into the wrapped food commodity.

Tansy (Tanacetum vulgare) is a common plant used in folk medicine for digestive problems, fevers, and migraines; against parasites; and as an insect repellent. The active substances in essential oil are responsible for its antimicrobial and antioxidant activity. Thus, tansy essential oil (TO) was added to alginate films to fabricate materials with antioxidant and antibacterial properties for food packaging. Sodium alginate films with glycerol and TO were tested in terms of structure, mechanical, thermal, antioxidant, and antibacterial properties. The structure of the films was examined using SEM and an ATR-FTIR spectrophotometer. The addition of TO to the alginate film significantly changed the films’ microstructure, making them rougher and porous. A low-intensity band at 1739 cm−1, indicative of the presence of TO, appeared in all spectra of alginate films with TO. Moreover, the studies revealed that essential oil acted as a plasticizer, slightly reducing tensile strength from about 7 MPa to 5 MPa and increasing elongation at break from 52% to 56% for the sample with 2% TO. The alginate films enriched in TO exhibited antioxidant properties (280 μmol Trolox/100 g of the sample with 2% TO) and antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.

Due to natural agents and human activities, large quantities of microplastics enter the marine environment. As an emerging pollutant, MPs have attracted worldwide attention and become a great challenge in recent years. Sodium alginate is a kind of natural polysaccharide with non-toxic, stability, and low cost. In this study, sodium alginate sponge was prepared by secondary freeze-drying technology. Alginate sponge contains a large number of hydrophilic groups; thus, alginate sponge has super water-absorbed (the water absorption rate range from 1193–5232%). Meanwhile, the alginate sponge has high porosity of 81.93% and excellent mechanical properties. The removal efficiency of 100 mg·L −1 microplastics by alginate sponge reached up to 92.3%. The 1 mg·L −1 and 10 mg·L −1 microplastics can be completely absorbed in 27 h and 60 h, respectively. The adsorption mechanism of microplastics adsorbed onto alginate sponge included intra-particle diffusion, hydrogen bonds interactions, and π-π interactions. In addition, the adsorption of MPs loaded Cu 2+ /Na + by sponge in complex aqueous environments is still significant. This study expands the development prospect of sodium alginate sponge materials in the field of water treatment and provides a new green approach for the removal of microplastics. Graphical abstract

The main goal of this research was to create biocompatible hydrogels using gelatin and a double cross-linking technique involving both covalent and ionic bonds to immobilize propolis. The covalent bonds were formed through Schiff base cross-links between protein-free amino groups (NH2) from the lysine residue and aldehyde groups (CHO) produced by oxidizing sodium alginate with NaIO4, while the ionic bonds were achieved using Mg2+ ions. Hydrogel films were obtained by varying the molar ratios of –CHO/–NH2 under different pH conditions (3.5 and 5.5). The presence of aldehyde groups in the oxidized sodium alginate (OSA) was confirmed using FTIR and NMR spectroscopy. The oxidation degree was monitored over 48 h, and the influence of temperature was examined. Results showed that higher –CHO/–NH2 molar ratios led to increased conversion index values of NH2 groups, and a decrease in swelling degree values was observed in mediums with pH values of 5.5 and 7.4. The encapsulation and release efficiency of propolis decreased with an increase in the hydrogel cross-linking degree. UV irradiation enhanced the antioxidant activity of both free and encapsulated propolis. These findings offer valuable insights for the biomedical and pharmaceutical fields into designing biocompatible hydrogels for propolis immobilization, with potential for controlled release.

The aim of the current work was to produce sodium alginate (SA) maltodextrins (MD) based functional films incorporated with phenolic extract of Azolla pinnata leaves fern (AF) by solution molding technique. AF with different concentrations (0.8, 1.2 and 1.6% w/w) were integrated inside SA.MD films. The resulted films were characterized to investigate the surface structure by scanning electron microscope (SEM), thermal disposal by (DSC), crystallization by X-ray diffraction (XRD), potential interaction by (FT-IR) and some mechanical properties. The SEM micrographs indicated that the higher concentration (1.6%) of AF extract caused development of wrinkles on the surface of films. And as a result, there were a significant decrease of elongation at break (EB) and tensile strength properties of films to 55.01 and 58.42%, respectively. By continues addition of AF extract to SA.MD films, the film thickness increased from 0.124 to 0.181 mm, the scavenging and antimicrobial properties were enhanced by the attendance of ferulic acid, rutin, thiamine, tamarixetin, astragalin, quercetin, chlorogenic acid and epicatechin inside extracts. Furthermore, the films solubility, swelling degree and water vapor permeability were decreased to 13.08%, 26.41% and 1.662 × 10− 10 g H2O/m s p.a. The resulted films could be utilized as composite packaging material for different food applications.