Preparation and properties of alginate superabsorbent filament fibers crosslinked with glutaraldehyde

Diverse Approaches in Wet-Spun Alginate Filament Production from the Textile Industry Perspective: From Process Optimization to Composite Filament Production

Alginate, categorized as a natural-based biodegradable polymer, stands out for its inherently exclusive properties. Although this unique polymer is widely processed using film, coating, and membrane technologies for different usage areas, textile applications are still limited. This study aims to compile promising approaches that will pave the way for the use of wet-spun alginate filaments in textile applications. In this regard, this study provides information about the molecular structure of alginate, the gel formation mechanism, and cross-linking using different techniques. Our literature review categorizes parameters affecting the mechanical properties of wet-spun alginate filaments, such as the effect of ion source and spinning dope concentration, needle diameter, temperature, and coagulants. Following this, a detailed and comprehensive literature review of the various approaches, such as use of additives, preparation of blended filaments, and grafted nanocrystal addition, developed by researchers to produce composite alginate filaments is presented. Additionally, studies concerning the use of different cations in the coagulation phase are reported. Moreover, studies about the functionalism of wet-spun alginate filaments have been offered.

Progress on green crosslinking of polysaccharide hydrogels for drug delivery and tissue engineering applications

Natural polysaccharides are being studied for their biocompatibility, biodegradability, low toxicity, and low cost in the fabrication of various hydrogel devices. However, due to their insufficient physicochemical and mechanical qualities, polysaccharide hydrogels alone are not acceptable for biological applications. Various synthetic crosslinkers have been tested to overcome the drawbacks of standalone polysaccharide hydrogels; however, the presence of toxic residual crosslinkers, the generation of toxic by-products following biodegradation, and the requirement of toxic organic solvents for processing pose challenges in achieving the desired non-toxic biomaterials. Natural crosslinkers such as citric acid, tannic acid, vanillin, gallic acid, ferulic acid, proanthocyanidins, phytic acid, squaric acid, and epigallocatechin have been used to generate polysaccharide-based hydrogels in recent years. Various polysaccharides, including cellulose, alginate, pectin, hyaluronic acid, and chitosan, have been hydrogelized and investigated for their potential in drug delivery and tissue engineering applications using natural crosslinkers. We attempted to provide an overview of the synthesis of polysaccharide-based hydrogel systems (films, complex nanoparticles, microspheres, and porous scaffolds) based on green crosslinkers, as well as a description of the mechanism of crosslinking and properties with a special emphasis on drug delivery, and tissue engineering applications.

Research Advances in Superabsorbent Polymers

Superabsorbent polymers are new functional polymeric materials that can absorb and retain liquids thousands of times their masses. This paper reviews the synthesis and modification methods of different superabsorbent polymers, summarizes the processing methods for different forms of superabsorbent polymers, and organizes the applications and research progress of superabsorbent polymers in industrial, agricultural, and biomedical industries. Synthetic polymers like polyacrylic acid, polyacrylamide, polyacrylonitrile, and polyvinyl alcohol exhibit superior water absorption properties compared to natural polymers such as cellulose, chitosan, and starch, but they also do not degrade easily. Consequently, it is often necessary to modify synthetic polymers or graft superabsorbent functional groups onto natural polymers, and then crosslink them to balance the properties of material. Compared to the widely used superabsorbent nanoparticles, research on superabsorbent fibers and gels is on the rise, and they are particularly notable in biomedical fields like drug delivery, wound dressing, and tissue engineering.

Formalin-casein enhances water absorbency of calcium alginate beads and activity of encapsulated Metarhizium brunneum and Saccharomyces cerevisiae

The control of root-feeding wireworms has become more challenging as synthetic soil insecticides have been progressively phased out due to environmental risk concerns. Innovative microbial control alternatives such as the so-called attract-and-kill strategy depend on the rapid and successful development of dried encapsulated microorganisms, which is initiated by rehydration. Casein is a functional additive that is already used in food or pharmaceutical industry due to its water binding capacity. Cross-linked forms such as formalin-casein (FC), exhibit altered network structures. To determine whether FC influences the rehydration of alginate beads in order to increase the efficacy of an attract-and-kill formulation for wireworm pest control, we incorporated either casein or FC in different alginate/starch formulations. We investigated the porous properties of alginate/starch beads and subsequently evaluated the activities of the encapsulated entomopathogenic fungus Metarhizium brunneum and the CO₂ producing yeast Saccharomyces cerevisiae. Adding caseins altered the porous structure of beads. FC decreased the bead density from (1.0197 ± 0.0008) g/mL to (1.0144 ± 0.0008) g/mL and the pore diameter by 31%. In contrast to casein, FC enhanced the water absorbency of alginate/starch beads by 40%. Furthermore, incorporating FC quadrupled the spore density on beads containing M. brunneum and S. cerevisiae, and simultaneous venting increased the spore density even by a factor of 18. Moreover, FC increased the total CO₂ produced by M. brunneum and S. cerevisiae by 29%. Thus, our findings suggest that rehydration is enhanced by larger capillaries, resulting in an increased water absorption capacity. Our data further suggest that gas exchange is improved by FC. Therefore, our results indicate that FC enhances the fungal activity of both fungi M. brunneum and S. cerevisiae, presumably leading to an enhanced attract-and-kill efficacy for pest control.

Approaches in Animal Proteins and Natural Polysaccharides Application for Food Packaging: Edible Film Production and Quality Estimation

Natural biopolymers are an interesting resource for edible films production, as they are environmentally friendly packaging materials. The possibilities of the application of main animal proteins and natural polysaccharides are considered in the review, including the sources, structure, and limitations of usage. The main ways for overcoming the limitations caused by the physico-chemical properties of biopolymers are also discussed, including composites approaches, plasticizers, and the addition of crosslinking agents. Approaches for the production of biopolymer-based films and coatings are classified according to wet and dried processes and considered depending on biopolymer types. The methods for mechanical, physico-chemical, hydration, and uniformity estimation of edible films are reviewed.

Development and Characterization of Xanthan Gum and Alginate Based Bioadhesive Film for Pycnogenol Topical Use in Wound Treatment

Pycnogenol (PYC) is a concentrate of phenolic compounds derived from French maritime pine; its biological activity as antioxidant, anti-inflammatory and antibacterial suggests its use in the treatment of open wounds. A bioadhesive film, loaded with PYC, was prepared by casting, starting with a combination of two biopolymer acqueous solutions: xanthan gum (1% wt/wt) and sodium alginate (1.5% wt/wt), in a 2.5/7.5 (wt/wt) ratio. In both solutions, glycerol (10% wt/wt) was added as plasticizing agent. The film resulted in an adhesive capable to absorb a simulated wound fluid (~ 65% wt/wt within 1 h), therefore suitable for exuding wounds. The mechanical characterization showed that the film is deformable (elastic modulus E = 3.070 ± 0.044 MPa), suggesting adaptability to any type of surface and resistance to mechanical solicitations. PYC is released within 24 h by a sustained mechanism, achieving a maximum concentration of ~0.2 mg/mL, that is safe for keratinocytes, as shown by cytotoxicity studies. A concentration of 0.015 mg/mL is reached in the first 5 min after application, at which point PYC stimulates keratinocyte growth. These preliminary results suggest the use of PYC in formulations designed for topical use.

Preparation of Beebread Caviar from Buckwheat Honey through Immobilization with Sodium Alginate

Honeys have a pleasant taste and a wide range of use. They are characterized by a relatively high consumption compared to bee pollen or beebread. Honeys are the most popular bee products. Considering health reasons, beebread exhibits the strongest properties as it has the highest nutritional value as well as strong detoxifying, antioxidant, and antiradical properties. Despite having such valuable properties, consumption of beebread is negligible; sometimes, it is limited only to supplementation in case of diseases. This paper proposes a new food product, that is, beebread caviar made from buckwheat honey. The expiry date and sensory and physicochemical quality of beebread caviar have been determined in this study. Beebread caviar, obtained by immobilization on alginate carrier, contained 0.34 mg GAE/mL extract. It remained stable until five days after preparation. Its total acidity was 33.7 mval/kg. Its extract content was 22.53%. Caviar had a high overall sensory score of 4.8 points on a 5-point scale. Beebread caviar can be successfully classified as probiotic food because beebread contains a large amount of lactic acid. In the form of caviar, a new, attractive, and convenient form of beebread consumption could become one of the products of comfortable and functional food.

Alginate-Based Edible Films and Coatings for Food Packaging Applications

Alginate is a naturally occurring polysaccharide used in the bio industry. It is mainly derived from brown algae species. Alginate-based edible coatings and films attract interest for improving/maintaining quality and extending the shelf-life of fruit, vegetable, meat, poultry, seafood, and cheese by reducing dehydration (as sacrificial moisture agent), controlling respiration, enhancing product appearance, improving mechanical properties, etc. This paper reviews the most recent essential information about alginate-based edible coatings. The categorization of alginate-based coatings/film in food packaging concept is formed gradually with the explanation of the most important titles. Emphasis will be placed on active ingredients incorporated into alginate-based formulations, edible coating/film application methods, research and development studies of coated food products and mass transfer and barrier characteristics of the alginate-based coatings/films. Future trends are also reviewed to identify research gaps and recommend new research areas. The summarized information presented in this article will enable researchers to thoroughly understand the fundamentals of the coating process and to develop alginate-based edible films and coatings more readily.

Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs) seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials.

Electrospinning of natural polymers for advanced wound care: towards responsive and adaptive dressings

Nanofibrous dressings produced by electrospinning proteins and polysaccharides are highly promising candidates in promoting wound healing and skin regeneration.

Synthesis and Characterization of Chitosan & Amino Acid Superabsorbent Hydrogels

Chitosan & L-alanine and chitosan & L-leucine superabsorbent hydrogels were prepared by crosslinking chitosan with glutaraldehyde. L-alanine and L-leucine were used as amino acid structures in different loading degrees and the optimum amount of amino acid was determined for both types of hydrogel. The swelling behaviors of neat chitosan, chitosan & L-alanine and chitosan & L-leucine hydrogels were investigated by gravimetric measurements with different pH values and at different intervals of time. The neat chitosan, chitosan & L-alanine and chitosan & L-leucine hydrogels were characterized by Fourier transform infrared spectroscopy (FT-IR). Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) were used to find the thermal stability of the hydrogels. Also, surface morphological studies of all the hydrogels were carried out by using a Scanning Electron Microscope (SEM). In addition, XRD analysis demonstrated significant changes in the characteristic and morphological structures of the hydrogels.

Fabrication and assessment of polyacrylate/(guar gum modified bentonite) superabsorbent polymeric composite

A superabsorbent composite was synthesized via polymerization in a complete aqueous environment. A polymeric composites was fabricated effectively by varying the concentration of natural gum and crosslinker. Reinforcing of the polymer chains with bentonite sheets was confirmed by Fourier transform infrared (FTIR) spectra. X-ray diffraction (XRD) revealed that bentonite was exfoliated and dispersed in the polymeric matrix. Scanning electron microscopy (SEM) and thermal analysis (TGA/DSC/DTA) were used to study the morphology and thermal stability of the composites, respectively. The effects of natural gum and crosslinker were investigated. Results showed that introducing organic-inorganic composites improved the swelling capability and water retention ability of the superabsorbent.

Synthesis of Starch—Poly(Sodium Acrylate-co-Acrylamide) Superabsorbent Hydrogel with Salt and pH-Responsiveness Properties as a Drug Delivery System

The synthesis and swelling behavior of a superabsorbent hydrogel based on starch (St) and polyacrylonitrile (PAN) were investigated. The physical mixture of St and PAN was hydrolyzed with NaOH solution to yield St—poly(sodium acrylate-co-acrylamide) superabsorbent hydrogels. The nitrile groups of PAN were completely converted to a mixture of hydrophilic carboxamide and carboxylate groups during the basic hydrolysis followed by in situ crosslinking of the PAN chains by the starch alkoxide ions. A mechanism for hydrogel formation was proposed and the structure of the product was established using FTIR spectroscopy. The effect of reaction variables, such as, base concentration, hydrolysis time, and temperature were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The optimized swelling capacity in distilled water was found to be >500g/g. The absorbency of the hydrogels indicated that the swelling ratios decreased with ionic strength increases. The St—poly(sodium acrylate-co-acrylamide) hydrogel exhibited a pH-responsive swelling—deswelling behavior at pH's 2 and 8. This on—off switching behavior provides the hydrogel with the potential to control delivery of bioactive agents. Release profiles of ibuprofen (IBU), a poor watersoluble drug, from the hydrogels were studied under both simulated gastric and intestinal pH conditions. The release was much quicker at pH 7.4 than at pH 1.2. The swelling rates of the hydrogels with various particle sizes were investigated as well.

Elastic, superporous hydrogel hybrids of polyacrylamide and sodium alginate

A novel approach was developed to prepare a superporous hydrogel with superior mechanical and elastic properties. According to this method, a synthetic monomer was polymerized and crosslinked in the presence of a water-soluble alginate polymer. Later in the process, the alginate part of the synthesized hydrogel was treated with metal cations, which resulted in a hydrogel hybrid with an interpenetrating network structure. In this article, a hydrogel hybrid of acrylamide and alginate is highlighted because of its unique swelling and mechanical properties. This hydrogel hybrid shows resilience and a rubbery property in its fully water-swollen state, which not previously been reported. To help understand the underlying mechanism responsible for such unique properties with hydrogel hybrids, the ionotropic gelation of the alginate polymer was also studied in more detail.