► Alginates can be crosslinked with various cations to modify the characteristics of the resultant matrices for different applications. ► New strategies have been successfully employed to improve the ...gelation mechanism of alginates. ► Innovative wound dressings with haemostatic, absorbent and antimicrobial properties have been developed. ► A number of patents involving alginate formulations for cell transplant have emerged. ► Alginates can be employed for rapid, as well as prolonged delivery of bioactive compounds.
This review outlines the role of alginates in microencapsulation and therapeutic applications. It focuses on the physicochemical properties of alginates (e.g. viscosity, thermo-stability, sol–gel transformation and drug release) to gain better insight into their potential medical applications, particularly for wound care and therapeutics. In order to understand how alginates can be optimized as a useful delivery system for therapeutic applications, various factors that impact drug release from alginate matrices (e.g. types of cations used in cross-linking, porosity of alginate matrices, pH effect, alginate composition, molecular weight of encapsulated drugs and modification of the functional groups in alginates) are also discussed. More specifically, practical applications of the cross-linking mechanism and sol–gel transformation property of alginates are explored to assess their potential to improve the mechanical properties of alginate dressings, to impart anti-microbial properties for treating wound infections and to develop products for tissue repair and wound healing. Innovative processes of developing alginate carriers and delivery systems and their recent applications are also discussed. Strategies employed to improve gelation of alginates commonly target the formulation by the inclusion of non-gelling cations or sequestrants during cross-linking. The application of other strategies, such as hot-made alginate gel method,
in situ gelation method, crystal gun method, acoustic excitation method, and the use of extrusion devices with improved design are reviewed.
Bioplastics are plastics made from renewable raw materials such as polysaccharides, proteins and lipids. One of the alternative sources of bioplastic raw materials is hydrocolloid from seaweed, which ...is abundantly available in Indonesia, so that this hydrocolloid-based bioplastic is very prospective to be developed, and can increase the added value of seaweed. The physical and mechanical properties of alginate bioplastics can be improved by combining them with other materials into biocomposite materials that have superior properties and meet specifications. This study aims to determine the effect of calcium chloride (CaCl2) on the physical and mechanical properties of the CMC-Glycerol-Alginate composite bioplastic from Sargassum sp. Bioplastics were made by mixing 0.5 g of alginate flour, added CMC (1.5 g), and 100 ml of distilled water, then stirred with a magnetic stirrer for 10 minutes at 90oC. After that, the temperature was lowered to 40oC and 5 ml of glycerol was added and then homogenized again for 15 minutes. The mixture was filtered and then poured into a glass mold and the surface was leveled using a stainless steel cylinder, then dried in an oven at 80oC for 12 hours. After that the bioplastic is released from the glass plate. In the soaking method, the bioplastic sheets were immersed in a 2% CaCl¬2 solution for 5 minutes, then dried and stored in a desiccator. In the mixing method, 1 gram of CaCl¬2 was put directly into the alginate-CMC-glycerol mixture and homogenized with a magnetic stirrer at 90oC for 15 minutes, then printed on a glass plate, then dried at 100oC for 12 hours. CaCl2 treatment by mixing and soaking decreased elongation, tensile strength, biodegradability and transparency, but increased water resistance and thickness of the alginate-CMC-glycerol composite bioplastic, and changed the surface properties of the bioplastic to be rougher. No new functional groups were formed due to the interaction between alginate, CMC, glycerol, distilled water and CaCl2. Bioplastik adalah plastik yang dibuat dari bahan baku terbarukan seperti polisakarida, protein dan lipida. Salah satu alternatif sumber bahan baku bioplastik adalah hidrokoloid dari rumput laut yang tersedia melimpah di Indonesia, sehingga bioplastik berbahan hidrokoloid ini sangat prospektif untuk dikembangkan, serta dapat meningkatkan nilai tambah rumput laut.Sifat fisik dan mekanik bioplastik alginat dapat ditingkatkan dengan cara dikombinasi dengan bahan lain menjadi material biokomposit yang memiliki sifat unggul dan memenuhi spesifikasi.Penelitian ini bertujuan untuk mengetahui pengaruh kalsium klorida (CaCl2) terhadap sifat fisik dan mekanik bioplastik komposit CMC- Gliserol-Alginat dari Sargassum sp.Bioplastik dibuat mdengan mencampurkan tepung alginat sebanyak 0,5 g ditambahkan CMC ( 1,5 g), dan akuades 100 ml, lalu diaduk dengan magnetic stirrer selama 10 menit pada suhu 90oC. Setelah itu, suhu diturunkan sampai 40oC dan ditambahkan gliserol 5 ml lalu dihomogenkan lagi selama 15 menit. Campuran disaring lalu dituang dalam cetakan kaca dan diratakan permukaannya menggunakan silinder stainless steel, kemudian dikeringkan dalam oven pada suhu 80oC selama 12 jam. Setelah itu bioplastik dilepaskan dari pelat kaca. Pada metoda soaking lembaran bioplastik direndam dalam larutan CaCl2 2% selama 5 menit, lalu dikeringkan dan disimpan dalam desikator. Pada metoda mixing, CaCl2 sebanyak 1 gram dimasukkan langsung ke dalam campuran alginat-CMC-gliserol dan dihomogenkan dengan magnetic stirrer pada suhu 90oC selama 15 menit, lalu dicetak dalam pelat kaca, lalu dikeringkan pada suhu 100oC selama 12 jam. Perlakuan CaCl2 dengan cara mixing dan soaking menurunkan elongasi, kuat tarik, biodegradabilitas dan transparansi, tetapi meningkatkan ketahanan air dan ketebalan bioplastik komposit alginat-CMC-gliserol, serta mengubah sifat permukaan bioplastik menjadi lebih kasar. Tidak terdapat gugus fungsi baru yang terbentuk akibat interaksi antara alginat, CMC, gliserol, akuades dan CaCl2.
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•Honey/SA/PVA nanofibers were fabricated via all-aqueous electrospinning.•The effect of honey content on the swelling ratio of membrane was investigated.•Honey enhanced the ...antioxidant and antibacterial activities of nanofibers.•Honey/SA/PVA nanofiber membrane exhibited good biocompatibility.
Honey is an ancient natural wound-healing agent and has been reintroduced to modern clinical wound care as it has various bioactivities. In this study, honey was incorporated into an alginate/PVA-based electrospun nanofibrous membrane to develop an efficient wound dressing material. The morphology and chemical composition of the nanofibrous membrane were observed by scanning electron microscopy and characterized via Fourier transform infrared spectroscopy, respectively, demonstrating that honey was successfully introduced to the nanofibers. The nanofibrous membranes with increasing honey content showed enhanced antioxidant activity, suggesting the ability to control the overproduction of reactive oxygen species. Disc diffusion assay and dynamic contact assay proved the antibacterial activity of the honey loaded nanofibers towards Gram-positive bacterium (Staphylococcus aureus) and Gram-negative bacterium (Escherichia coli). The cytotoxicity assay illustrated the non-cytotoxicity and biocompatibility of the nanofibrous membranes. Therefore, the developed honey/alginate/PVA nanofibrous membranes are promising for wound dressings.
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•Dual-physically cross-linked double network endows hydrogel recoverability and fatigue resistance.•Ca2+ ions provide hydrogel excellent strain-sensitive conductivity.•The hydrogel ...can be assembled as wearable strain sensor to monitor human-motions.•The monitor of slight physiological activities like talking and breathing were achieved.
Soft, stretchable, and elastic hydrogels have recently attracted immense interest due to their potential applications in wearable strain sensors. However, most of hydrogel-based sensors exhibit poor mechanical properties. Here, a robust, flexible and strain-sensitive conductive wearable sensor is prepared based on dual physically cross-linked double network hydrogels consisting of core-shell hybrid nanoparticles cross-linked polyacrylamide as first network and Ca2+ cross-linked alginate as second network. Dynamic physical cross-linking as sacrifice bonds can effectively dissipate energy and reconstruct the network structure, endowing hydrogels with high strength, toughness, stretchability and excellent self-recovery properties. Moreover, the hydrogels exhibit outstanding strain sensitive behavior with repeatable, stable, and precise changes in resistance signals. Based on the excellent strain sensitivity, the hydrogel can be assembled as a wearable strain sensor to monitor joint motions such as finger, wrist, elbow, neck, and knee joints, and even the slight motions including breathing and speaking. Thus, the tough, anti-fatigue, self-recovery and conductive hydrogels have promising potential as soft, high-performance and flexible wearable strain sensor for soft robots, biomimetic prostheses, human activity monitoring and health-monitoring systems.
Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical ...features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to −70 °C and are stable under ambient conditions or even vacuum.
Anti‐freezing, non‐drying tough organohydrogels are fabricated by a solvent displacement strategy. Water molecules in the hydrogels are partially displaced by cryoprotectants, as inspired by the cryopreservation of biological samples. This method opens a way to rationally tune the freezing and drying tolerance for many water‐based hydrogels.
•Agar is a sulfated galactan synthesized in the cell wall matrix of red seaweeds.•The gaps in current knowledges on agar biosynthesis in red seaweeds are reviewed.•Development of molecular markers ...for the selection of seaweeds is also discussed.
Agar is a jelly-like biopolymer synthesized by many red seaweeds as their major cell wall component. Due to its excellent rheological properties, it has been exploited commercially for applications in food, cosmetic, pharmaceutical, biomedical and biotechnology industries. Despite its multiple uses, the biosynthesis of this phycocolloid is not fully understood. The current knowledge on agar biosynthesis is inferred from plant biochemistry and putative pathways for ulvan and alginate biosynthesis in green and brown seaweeds, respectively. In this review, the gaps in our current knowledge on agar biosynthetic pathway are discussed, focusing on the biosynthesis of agar precursors, elongation of agar polysaccharide chain and side chain modification. The development of molecular markers for the screening of desired seaweeds for industrial exploitation is also discussed.
A smart valve is created by 4D printing of hydrogels that are both mechanically robust and thermally actuating. The printed hydrogels are made up of an interpenetrating network of alginate and ...poly(N‐isopropylacrylamide). 4D structures are created by printing the “dynamic” hydrogel ink alongside other static materials.
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Hydrogel-based wound dressings are one of the most promising materials in wound care, fulfilling important dressing requirements, including: (a) keeping the wound moist whilst ...absorbing extensive exudate, (b) adhesion-free coverage of sensitive underlying tissue, (c) pain reduction through cooling and (d) a potential for active intervention in the wound healing process. Although numerous hydrogel-based dressings are already on the market, new wound care treatment options are urgently required to address the growing number of severe, acute and chronic wounds experienced by today’s aging society. High cost, safety concerns surrounding the use of drugs and allogeneic/xenogeneic materials, and issues specific to hydrogels, such as lack of mechanical stability, are impeding clinical implementation of many novel approaches. To meet clinical needs, the development of new hydrogel wound dressings that overcome these drawbacks would be desirable. This review provides a broad overview of recent progress – commercial and scientific – in the field of bioactive hydrogel wound dressings. A variety of approaches to bioactive wound healing, such as bioactive dressing materials, use of antimicrobial agents, inclusion of biological signaling molecules like growth factors, and incorporation of seeded stem cells, are considered and critically evaluated.
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