Fabrication, Property and Application of Calcium Alginate Fiber: A Review

Alginate Capsules: Versatile Applications and Production Techniques

Alginate is a natural polysaccharide commonly obtained from brown algae and is usually used in the food industry as an additive, specifically as a thickening, gelling, and emulsifying agent. Due to its polyanionic nature, it can crosslink in the presence of divalent or trivalent cations. This crosslinking process involves the formation of chemical bonds between the carboxylic groups of parallel chains, resulting in a solid structure. In this way, compounds of interest can be enclosed in a capsule or a bead. Thanks to this ability, possible applications of alginate capsules are countless: it is possible to range from the pharmaceutical to the nutritional fields, from the agri-food industry to the textile or cosmetic sectors. These capsules can protect the encapsulated ingredients, promote their delivery or controlled release, or be imagined as small-scale reactors. The present review describes the main techniques used to produce alginate capsules, and several examples of possible application fields are shown.

Modulating the Properties of Brown Alga Alginate-Based Fibers Using Natural Cross-Linkers for Sustainable Textile and Fashion Applications

Seaweed-derived alginate shows promise in the textile industry as a sustainable alternative to synthetic and natural materials. However, challenges arise due to its low mechanical strength. We addressed this limitation by sustainably extracting alginates from European brown algae and employing novel manufacturing methods. Using natural cross-linkers, such as chitosan, ferulic acid, and citric acid, we have successfully modulated the mechanical properties of alginate fibers. Mechanical properties of ferulic acid and citric acid-cross-linked alginate solutions were spinnable, producing fibers with a diameter of 73-75 μm. Ferulic acid cross-linked alginate fibers exhibited stiffness, with a tensile strength of 52.97 MPa and a strain percentage of 20.77, mechanical properties comparable to those of wool, polyester, and rayon. In contrast, citric acid-cross-linked fibers showed partial elasticity, with a tensile strength of 14.35 MPa and a strain percentage of 45.53, comparable to those of nylon. This ability to control the mechanical properties of seaweed-derived fibers represents a significant advancement for their application in sustainable textiles and the fashion industry.

Alginate as a Sustainable and Biodegradable Material for Medical and Environmental Applications-The Case Studies

Alginates are salts of alginic acid derived mainly from sea algae of the genus brown algae. They are also synthesized by some bacteria. They belong to negatively charged polysaccharides exhibiting some rheological properties. High plasticity and the ability to modify the structure are the reasons for their application in numerous industries. Moreover, when in contact with the living tissue, they do not trigger an immune response, and for this reason they are the most often tested materials for medical applications. The paper discusses the latest applications, including 3D bioprinting, drug delivery systems, and sorptive properties. Recognizing alginates as biomaterials, it emphasizes the necessity for precise processing and modification to industrialize them for specific uses. This review aims to provide a thorough understanding of the advancements in alginate research, underscoring their potential for innovative applications.

Highly-Strong and Highly-Tough Alginate Fibers with Photo-Modulating Mechanical Properties

The good combination of high strength and high toughness is a long-standing challenge in the design of robust biomaterials. Meanwhile, robust biomaterials hardly perform fast and significant mechanical property changes under the trigger of light at room temperature. These limit the application of biomaterials in some specific areas. Here, photoresponsive alginate fibers are fabricated by using the designed azobenzene-containing surfactant as flexible contact point for cross-linking polysaccharide chains of alginate, which gain high mechanics through reinforced plastic strain and photo-modulating mechanics through isomerization of azobenzene. By transferring molecular motion into macro-scale mechanical property changes, such alginate fibers achieve reversible photo-modulations on the mechanics. Their breaking strength and toughness can be photo-modulated from 732 MPa and 112 MJ m-3 to 299 MPa and 27 MJ m-3, respectively, leading to record high mechanical changes among the developed smart biomaterials. With merits of good tolerance to pH and temperature, fast response to light, and good biocompatibility, the reported fibers will be suitable for working in various application scenarios as new smart biomaterials. This study provides a new design strategy for gaining highly-strong and highly-tough photoresponsive biomaterials.

Cell-Based Meat Scaffold Based on a 3D-Printed Starch-Based Gel

Starch was mixed with a gel to produce a starch-based gel ink, which exhibited favorable printing characteristics. Through the optimization of infill density, 3D-printed scaffolds with 50% infill density and a highly ordered microstructure were successfully fabricated. The addition of calcium carbonate nanoparticles-glucono delta lactone (CaCO3 NPs-GDL) had notable effects on the swelling degree, in vitro digestion, water stability, and pore distribution of the scaffolds. When the amount of CaCO3 NPs in the starch-based gel was 0.075 g, the resulting 3D-printed gel scaffold with a 50% infill density proved to be the most suitable for cultivating cell-based meat. It featured pore sizes ranging from 80 to 120 μm and a compression modulus of 246.76 Pa. After 7 days of proliferation, the C2C12 mouse skeletal myoblasts exhibited an approximately 2.81-fold increase in cell numbers. The fusion index and maturation index of C2C12 cells on the scaffolds were 57.00 ± 0.45% and 34.56 ± 0.56%, respectively. The starch-based gel scaffolds demonstrated excellent water stability and in vitro degradability. Moreover, C2C12 cells exhibited successful proliferation and differentiation on the starch-based scaffolds, ultimately leading to the production of cell-based meat. This study developed a starch-based composite gel scaffold for the manufacture of cell-based meat.

Using celluloses to reinforce the optimized alginate film in wet state: Effect of cellulose types and cooking treatment

Alginate (Alg) as co-extruded casing is of interest to the meat industry as replacers for natural sausage casing. However, these studies on the mechanical reinforcement of Alg-based film are still limited in the wet state (e.g. co-extrusion process). In this work, Alg-D with the highest viscosity-average molecular weight (1.12 × 105) was selected from four types of alginates based on the results of the viscosity of Alg solutions and film strength. Next, three celluloses (cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and microfibrillated fiber (MFC)) were added to the Alg-D matrix at different concentrations. SEM showed that the cross section of the Alg-based films became more compact and uniform when the size of celluloses decreased. The tensile test revealed that the strength (TS) of Alg-based films exhibited an initial increase followed by a subsequent drop as the cellulose content rose. The best mechanical strengthening effect was the Alg-CNC film (1.16 MPa), which increased by 93.33 % compared with that of pure Alg. Cooking treatment could further enhance this trend. The opacity increased gradually with the increase of cellulose content, while these films were still transparent enough for food packaging. These findings would have potential applications in food packaging, especially co-extruded sausage casings.

Carbon-based single-atom catalysts derived from biomass: Fabrication and application

Single-atom catalysts (SACs) with active metals dispersed atomically have shown great potential in heterogeneous catalysis due to the high atomic utilization and superior selectivity/stability. Synthesis of SACs using carbon-neutral biomass and its components as the feedstocks provides a promising strategy to realize the sustainable and cost-effective SACs preparation as well as the valorization of underused biomass resources. Herein, we begin by describing the general background and status quo of carbon-based SACs derived from biomass. A detailed enumeration of the common biomass feedstocks (e.g., lignin, cellulose, chitosan, etc.) for the SACs preparation is then offered. The interactions between metal atoms and biomass-derived carbon carriers are summarized to give general rules on how to stabilize the atomic metal centers and rationalize porous carbon structures. Furthermore, the widespread adoption of catalysts in diverse domains (e.g., chemocatalysis, electrocatalysis and photocatalysis, etc.) is comprehensively introduced. The structure-property relationships and the underlying catalytic mechanisms are also addressed, including the influences of metal sites on the activity and stability, and the impact of the unique structure of single-atom centers modulated by metal/biomass feedstocks interactions on catalytic activity and selectivity. Finally, we end this review with a look into the remaining challenges and future perspectives of biomass-based SACs. We expect to shed some light on the forthcoming research of carbon-based SACs derived from biomass, manifestly stimulating the development in this emerging research area.

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.

Seaweed as Basis of Eco-Sustainable Plastic Materials: Focus on Alginate

Seaweed, a diverse and abundant marine resource, holds promise as a renewable feedstock for bioplastics due to its polysaccharide-rich composition. This review explores different methods for extracting and processing seaweed polysaccharides, focusing on the production of alginate plastic materials. Seaweed emerges as a promising solution, due to its abundance, minimal environmental impact, and diverse industrial applications, such as feed and food, plant and soil nutrition, nutraceutical hydrocolloids, personal care, and bioplastics. Various manufacturing techniques, such as solvent casting, injection moulding, and extrusion, are discussed for producing seaweed-based bioplastics. Alginate, obtained mainly from brown seaweed, is particularly known for its gel-forming properties and presents versatile applications in many sectors (food, pharmaceutical, agriculture). This review further examines the current state of the bioplastics market, highlighting the growing demand for sustainable alternatives to conventional plastics. The integration of seaweed-derived bioplastics into mainstream markets presents opportunities for reducing plastic pollution and promoting sustainability in material production.

Recent advances in alginate-based composite gel spheres for removal of heavy metals

The discharge of heavy metal ions from industrial wastewater into natural water bodies is a consequence of global industrialisation. Due to their high toxicity and resistance to degradation, these heavy metal ions pose a substantial threat to human health as they accumulate and amplify. Alginate-based composite gels exhibit good adsorption and mechanical properties, excellent biodegradability, and non-toxicity, making them environmentally friendly heavy metal ion adsorbents for water with promising development prospects. This paper introduces the basic properties, cross-linking methods, synthetic approaches, modification methods, and manufacturing techniques of alginate-based composite gels. The adsorption properties and mechanical strength of these gels can be enhanced through surface modification, multi-component mixing, and embedding. The main production processes involved are sol-gel and cross-linking methods. Additionally, this paper reviews various applications of alginate composite gels for common heavy metals, rare earth elements, and radionuclides and elucidates the adsorption mechanism of alginate composite gels. This study aimed to provide a reference for synthesising new, efficient, and environmentally friendly alginate-based adsorbents and to contribute new ideas and directions for addressing the issue of heavy metal pollution.

Bioremediation of Hazardous Pollutants Using Enzyme-Immobilized Reactors

Bioremediation uses the degradation abilities of microorganisms and other organisms to remove harmful pollutants that pollute the natural environment, helping return it to a natural state that is free of harmful substances. Organism-derived enzymes can degrade and eliminate a variety of pollutants and transform them into non-toxic forms; as such, they are expected to be used in bioremediation. However, since enzymes are proteins, the low operational stability and catalytic efficiency of free enzyme-based degradation systems need improvement. Enzyme immobilization methods are often used to overcome these challenges. Several enzyme immobilization methods have been applied to improve operational stability and reduce remediation costs. Herein, we review recent advancements in immobilized enzymes for bioremediation and summarize the methods for preparing immobilized enzymes for use as catalysts and in pollutant degradation systems. Additionally, the advantages, limitations, and future perspectives of immobilized enzymes in bioremediation are discussed.

Progress in the Use of Hydrogels for Antioxidant Delivery in Skin Wounds

The skin is the largest organ of the body, and it acts as a protective barrier against external factors. Chronic wounds affect millions of people worldwide and are associated with significant morbidity and reduced quality of life. One of the main factors involved in delayed wound healing is oxidative injury, which is triggered by the overproduction of reactive oxygen species. Oxidative stress has been implicated in the pathogenesis of chronic wounds, where it is known to impair wound healing by causing damage to cellular components, delaying the inflammatory phase of healing, and inhibiting the formation of new blood vessels. Thereby, the treatment of chronic wounds requires a multidisciplinary approach that addresses the underlying causes of the wound, provides optimal wound care, and promotes wound healing. Among the promising approaches to taking care of chronic wounds, antioxidants are gaining interest since they offer multiple benefits related to skin health. Therefore, in this review, we will highlight the latest advances in the use of natural polymers with antioxidants to generate tissue regeneration microenvironments for skin wound healing.

Feasibility of Invasive Brown Seaweed Rugulopteryx okamurae as Source of Alginate: Characterization of Products and Evaluation of Derived Gels

Rugulopteryx okamurae (RO) is an invasive brown seaweed that causes severe environmental problems in the Mediterranean Sea. This work proposed an extraction method that enables their use as a raw material for producing sodium alginate. Alginate was successfully extracted from this invasive seaweed, with its gelling performance in the presence of Ca2+ ions comparable to existing commercial alginates. The mannuronic acid (M)-to-guluronic (G) acid ratio in the 1H-NMR profile indicated a higher percentage of G in the RO-extracted alginate, which implies a greater formation of so-called egg box structures. These differences resulted in their different rheological behaviour, as sodium alginate aqueous solutions exhibited a greater viscosity (η at 1 s-1 = 3.8 ± 0.052 Pa·s) than commercial alginate (2.8 ± 0.024 Pa·s), which is related to the egg box structure developed. When gelled in the presence of calcium, an increase in the value of the elastic modulus was observed. However, the value of the tan δ for the extracted alginate was lower than that of commercial alginate gels, confirming a structure more densely packed, which implies a different restructuring of the alginate chain when gelling. These results confirm the suitability of using invasive Rugulopteryx okamurae as a source of calcium alginate gels. In this way, sustainable bio-based materials may be produced from undesired biomass that currently poses a threat to the ecosystem.

Photochromic biomaterials: Synthesis and fluorescence properties of spiroxanthenes-grafted alginate derivatives

Herein, we reported a general and green synthetic strategy for photochromic functional alginate derivatives grafting with isoindolinone spiroxanthenes. Under mild condition, diverse 2-aminoalkyl isoindolinone spiroxanthene derivatives have been prepared from organic photochromic isobenzofuranone spiroxanthenes (including rhodamine B, rhodamine 6G and fluorescein), and grafted on alginate chains through amidation reaction using diamine as a linkage with water as a green solvent at room temperature. The photochromic properties of the fluorophores-modified polymers and the effect of pH value have been explored. Under acid conditions, the spiroisoindolinone rings of alginate derivatives are opened resulting in showing absorption bands and fluorescence with orange to green emission, while the alginate derivatives turned to colourless under basic conditions which is reversibly. In addition to biodegradability and biocompatibility, the polymers exhibit good film-forming properties simultaneously. The films and fibers produced from the alginate derivatives also project good fluorescence properties.

Study on the Permeability and Absorption Performance of the Crotch Layer in Seamless Knitted Period Underwear

During the physiological period, women have the problem of lateral and posterior leakage, and they expect to have period underwear that can reduce lateral and posterior leakage. This study is combined with menstrual needs, and in the crotch penetration layer, three types of yarns are used, seaweed viscose yarn, apocynum viscose yarn, and viscose yarn, as well as two fabric structures: honeycomb-shaped convex-concave stitching and grid-shaped convex point stitching. In the crotch absorption layer, three types of yarns are used, modal yarn, bamboo yarn, and viscose yarn, as well as two fabric structures: plush stitching and plain stitching. The above two parts establish a sample scheme according to full-factor experimental tests, and 12 knitted fabric samples were knitted. The experimental data were analyzed through SPSS one-way ANOVA. The results indicate that in terms of veil raw materials, the crotch penetration layer with seaweed viscose yarn has better penetration performance, while the crotch absorption layer with bamboo yarn has better absorption performance. In terms of fabric structure, the crotch penetration layer with grid-shaped convex point stitching has better penetration performance, while the crotch absorption layer with plush stitching has better absorption performance. This study provides a theoretical basis for the development of period underwear.

Eco-friendly phosphorus-free flame-retardant coating for microfiber synthetic leather via alginate-based layer-by-layer technology

The excellent comprehensive properties of microfiber synthetic leathers have led to their wide application in various aspects of our lives. However, the issue of flammability remains a significant challenge that needs to be addressed. Nowadays, the bio-based chemicals used in the flame-retardant materials have extremely grabbed our eyes. Herein, we developed an ecologically friendly flame-retardant microfiber synthetic leather using phosphorus-free layer-by-layer assembly technology (LBL) based on natural polysaccharide alginate (SA) coupled with polyethyleneimine (PEI) and 3-aminopropyltriethoxysilane (APTES). The effect of different LBL coating systems on the flame retardancy of microfiber synthetic leather was investigated. The results demonstrated that the introduction of APTES can completely inhibit the melt-dripping by enhancing char formation through silica elements. Furthermore, the trinary coating system consisting of SA/APTES/PEI exhibited excellent flame retardancy by combining gas-phase action from PEI and condensed-phase function from APTES. This modified microfiber synthetic leather showed a significantly higher limiting oxygen index (LOI) value of 33.0 % with no molten droplet. Additionally, the SA-based coating slightly suppressed the heat release, resulting in a 20 % reduction in total heat release during the combustion test. Overall, this work presents a facile and environmentally-friendly approach for achieving flame-retardant and anti-dripping microfiber synthetic leather.

Effect of the pre-crosslinking of Ba2+ ions on wet spinning of agar fibers

Decreased coagulation bath concentration and difficult recovery are classical issues observed during the wet spinning of fibers. In this paper, a novel method was presented for preparing environment-friendly agar fibers using deionized water as the coagulation and stretch baths. The addition of Ba2+ into the spinning solution increased the crosslinking time and improved the performance of spinning solution. The results showed that the introduction of Ba2+ in the spinning solution increased the viscosity of the spinning solution. Particularly, when the concentration of BaCl2 in the spinning solution was 7 wt%, the viscosity increased to 39.29 Pa·s, which made the molecular chain arrangement of agar more compact and ordered and promoted the gelation transformation of the spinning solution, resulting in an increase in the gel temperature from 0.2 °C (Ba-0/agar) to 5.4 °C (Ba-7/agar). The spinning solution was more conducive to the formation of fibers in deionized water. In addition, the physical and chemical properties of agar fibers were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The results showed that the use of deionized water as the coagulation bath can improve the color of fiber and solve the problem of fiber adhesion, whereas the mechanical strength of agar fibers with pre-cross-linking metal ions was also improved. For example, the breaking strength of Ba-7/agar/DIW was 0.73 cN/dtex while the breaking strength of Ba-0/agar/DIW was only 0.62 cN/dtex.

Fabrication and Performance of Bubble-Containing Multicompartmental Particles: Novel Self-Orienting Carriers

In this work, a class of bubble-containing multicompartmental particles with self-orienting capability is developed, where a single bubble is enclosed at the top of the super-segmented architecture. Such bubbles, driven by potential energy minimization, cause the particles to have a bubble-upward preferred orientation in liquid, enabling efficient decoding of their high-density signals in an interference-resistant manner. The particle preparation involves bubble encapsulation via the impact of a multicompartmental droplet on the liquid surface and overall stabilization via rational crosslinking. The conditions for obtaining these particles are systematically investigated. Methodological compatibility with materials is demonstrated by different hydrogel particles. Finally, by encapsulating cargoes of interest, these particles have found broad applications in actuators, multiplexed detection, barcodes, and multicellular systems.

Fully bio-based fire-safety composite from cotton/viscose wastes and alginate fiber as furniture materials

The increasing demand of textiles and apparel as global economy booms deepens environmental crisis associated with excessive textile waste disposed by landfill or incineration. This work implemented an eco-friendly and sustainable strategy to recycle up to 50 wt% textile waste with marine bio-based calcium alginate fiber into fire-proof fully bio-based composite textile by carding process. Incorporation of intrinsic nonflammable calcium alginate fibers endowed these needle-punching bio-composite felt with excellent inherent flame retardancy and improved safety. Horizontal burning test showed that by mixing with alginate fiber in proper ratio and pattern, extremely flammable cotton fiber and viscose fiber became totally inflammable. Analysis revealed that the generation of CaCO3 char residue and gaseous volatile of H2O inhibited the diffusion of O2 and heat, contributing to the outstanding fire proof performance of produced composite felt. The improved safety was affirmed by cone calorimetry test. It demonstrated limited heat, smoke and toxic volatile compound in the burning, as well as production of CO and CO2. All results showed that a straightforward yet economical method could recycle textile waste fibers into fully bio-based, fireproof and greener products, a potential candidate as fireproof structural filling and insulation materials for household textile or construction material.

Mechanical Properties of Alginate Hydrogels Cross-Linked with Multivalent Cations

Ionically, cross-linked alginate gels have a potential to be used in a wide range of biomedical, environmental and catalytic applications. The study deals with preparation of alginate hydrogels cross-linked with various cations and the analysis of their equilibrium swelling and mechanical properties. It is shown that the type of cations used in the cross-linking process affects the elastic moduli and the equilibrium degree of swelling of the gels. The experimental data in small-amplitude oscillatory tests are fitted with a model that involves two material parameters: the elastic modulus of a polymer network and a measure of its inhomogeneity. The influence of cations on these quantities is studied numerically. It is revealed that the dependence of the elastic modulus of ionically cross-linked alginate gels on their equilibrium degree of swelling differs from that predicted by the conventional theory for covalently cross-linked gels.

Synthesis and Characterization of a New Alginate/Carrageenan Crosslinked Biopolymer and Study of the Antibacterial, Antioxidant, and Anticancer Performance of Its Mn(II), Fe(III), Ni(II), and Cu(II) Polymeric Complexes

Natural polysaccharides are essential to a wide range of fields, including medicine, food, and cosmetics, for their various physiochemical and biological properties. However, they still have adverse effects limiting their further applications. Consequently, possible structural modifications should be carried out on the polysaccharides for their valorization. Recently, polysaccharides complexed with metal ions have been reported to enhance their bioactivities. In this paper, we synthesized a new crosslinked biopolymer based on sodium alginate (AG) and carrageenan (CAR) polysaccharides. The biopolymer was then exploited to form complexes with different metal salts including MnCl₂·4H₂O, FeCl₃·6H₂O, NiCl₂·6H₂O, and CuCl₂·2H₂O. The four polymeric complexes were characterized by Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, ultraviolet-visible spectroscopy (UV-Vis), magnetic susceptibility, molar conductivity methods, and thermogravimetric analysis. The X-ray crystal structure of the Mn(II) complex is tetrahedral and belongs to the monoclinic crystal system with the space group P121/n1. The Fe(III) complex is octahedral and crystal data fit with the cubic crystal system with the space group Pm-3m. The Ni(II) complex is tetrahedral and crystal data correspond to the cubic crystal arrangement with the space group Pm-3m. The data estimated for the Cu(II) polymeric complex revealed that it is tetrahedral and belongs to the cubic system with the space group Fm-3m. The antibacterial study showed significant activity of all the complexes against both Gram-positive bacteria (Staphylococcus aureus and Micrococcus luteus) and Gram-negative (Escherichia coli and Salmonella typhimurium) pathogenic strains. Similarly, the various complexes revealed an antifungal activity against Candida albicans. The Cu(II) polymeric complex recorded a higher antimicrobial activity with an inhibitory zone reaching 4.5 cm against Staphylococcus aureus bacteria and the best antifungal effect of 4 cm. Furthermore, higher antioxidant values of the four complexes were obtained with DPPH scavenging activity varying from 73 to 94%. The two more biologically effective complexes were then selected for the viability cell assessments and in vitro anticancer assays. The polymeric complexes revealed excellent cytocompatibility with normal human breast epithelial cells (MCF10A) and a high anticancer potential with human breast cancer cells (MCF-7) which increase significantly in a dose-dependent manner.

Advanced polymer hydrogels that promote diabetic ulcer healing: mechanisms, classifications, and medical applications

Diabetic ulcers (DUs) are one of the most serious complications of diabetes mellitus. The application of a functional dressing is a crucial step in DU treatment and is associated with the patient's recovery and prognosis. However, traditional dressings with a simple structure and a single function cannot meet clinical requirements. Therefore, researchers have turned their attention to advanced polymer dressings and hydrogels to solve the therapeutic bottleneck of DU treatment. Hydrogels are a class of gels with a three-dimensional network structure that have good moisturizing properties and permeability and promote autolytic debridement and material exchange. Moreover, hydrogels mimic the natural environment of the extracellular matrix, providing suitable surroundings for cell proliferation. Thus, hydrogels with different mechanical strengths and biological properties have been extensively explored as DU dressing platforms. In this review, we define different types of hydrogels and elaborate the mechanisms by which they repair DUs. Moreover, we summarize the pathological process of DUs and review various additives used for their treatment. Finally, we examine the limitations and obstacles that exist in the development of the clinically relevant applications of these appealing technologies. This review defines different types of hydrogels and carefully elaborate the mechanisms by which they repair diabetic ulcers (DUs), summarizes the pathological process of DUs, and reviews various bioactivators used for their treatment.

Potential use of seaweed polysaccharides as prebiotics for management of metabolic syndrome: a review

Seaweed polysaccharides (SPs) obtained from seaweeds are a class of functional prebiotics. SPs can regulate glucose and lipid anomalies, affect appetite, reduce inflammation and oxidative stress, and therefore have great potential for managing metabolic syndrome (MetS). SPs are poorly digested by the human gastrointestinal tract but are available to the gut microbiota to produce metabolites and exert a series of positive effects, which may be the mechanism by which SPs render their anti-MetS effects. This article reviews the potential of SPs as prebiotics in the management of MetS-related metabolic disturbances. The structure of SPs and studies related to the process of their degradation by gut bacteria and their therapeutic effects on MetS are highlighted. In summary, this review provides new perspectives on SPs as prebiotics to prevent and treat MetS.

Dissolvable Calcium Alginate Microfibers Produced via Immersed Microfluidic Spinning

Fabrication of micro- and nanofibers are critical for a wide range of applications from microelectronics to biotechnology. Alginate microfibers with diameters of tens to hundreds of microns play an important role in tissue engineering and fibers of these diameters are impossible to fabricate via electrospinning and can only be produced via fluidic spinning. Typically, microfluidic spinning based on photopolymerization produces fibers that are not easily dissolvable, while fluidic spinning with chemical cross-linking employs complex setups of microfabricated chips or coaxial needles, aimed at precise control of the fiber diameter; however, fluidic spinning introduces significant cost and complexity to the microfluidic setup. We demonstrate immersed microfluidic spinning where a calcium alginate microfiber is produced via displacement of alginate solution through a single needle that is immersed in a cross-linking bath of calcium chloride solution. The resulting diameter of the fiber is characterized and the fiber diameter and topology of the deposited fiber is related to the concentration of the alginate solution (2 wt%, 4 wt%, and 6 wt%), needle gauge (30 g, 25 g, and 20 g), and the volumetric flow rate of the alginate solution (1 mL/min, 2 mL/min, and 2.7 mL/min). The resulting fiber diameter is smaller than the internal diameter of the needle and this dependence is explained by the continuity of the flow and increased rate of fall of the liquid jet upon its issuing from the needle. The fiber diameter (demonstrated diameter of fibers range from 100 microns to 1 mm) depends weakly on the volumetric flow rate and depends strongly on the needle diameter. It also seems that for a smaller needle size, a greater concentration of alginate results in smaller diameter fibers and that this trend is not evident as the needle diameter is increased. In terms of topology of the deposited fiber, the higher wt% alginate fiber produces larger loops, while smaller wt% alginate solution yields a denser topology of the overlaid fiber loops. These fibers can be dissolved in DMEM/EDTA/DSC solution in 20-30 min (depending on the fiber diameter), leaving behind the hollow channels in the hydrogel matrix. We believe that the demonstrated simple setup of the immersed microfluidic spinning of the calcium alginate microfibers will be useful for creating tissue constructs, including the vascularized tissue implants.

Design of a New 3D Gelatin-Alginate Scaffold Loaded with Cannabis sativa Oil

There is an increasing medical need for the development of new materials that could replace damaged organs, improve healing of critical wounds or provide the environment required for the formation of a new healthy tissue. The three-dimensional (3D) printing approach has emerged to overcome several of the major deficiencies of tissue engineering. The use of Cannabis sativa as a therapy for some diseases has spread throughout the world thanks to its benefits for patients. In this work, we developed a bioink made with gelatin and alginate that was able to be printed using an extrusion 3D bioprinter. The scaffolds obtained were lyophilized, characterized and the swelling was assessed. In addition, the scaffolds were loaded with Cannabis sativa oil extract. The presence of the extract provided antimicrobial and antioxidant activity to the 3D scaffolds. Altogether, our results suggest that the new biocompatible material printed with 3D technology and with the addition of Cannabis sativa oil could become an attractive alternative to common treatments of soft-tissue infections and wound repair.

In Situ Generating CaCO3 Nanoparticles Reinforced Nonflammable Calcium Alginate Biocomposite Fiber

Petroleum-based synthetic flame-proof fiber releases toxic volatile organic compounds in thermal decomposition process and has other problems, like tickling feeling and high density. A natural polysaccharide, calcium alginate, is an intrinsic fire-resistant biodegradable material, but its limited mechanical performance prevents it from being a practical flame-retardant fabric. To address this problem, Na₂CO₃ was doped into alginate spinning solution to obtain in situ generating CaCO₃ nanoparticle-reinforced alginate fiber by microfluidic spinning technique. Comparative analysis illustrated that incorporation of 0.50% Na₂CO₃ into the fiber greatly improved its mechanical performance; meanwhile, in situ generated CaCO₃ nanoparticles also throttled oxygen and heat flow in burning, endowing the fiber with excellent flame retardancy. The prepared composite fiber released less heat, smoke, and toxic volatile organic compounds in burning, which reduced the fire hazard. The formed residue char and pyrolysis products functioned as the physical barrier and displayed a synergistic effect to inhibit oxygen and heat transmission and impede the further combustion. All of the results demonstrate that the obtained fiber exhibits a good mechanical and flame-retardant performance, making it an ideal candidate as a fire-protection textile.