![]() The pathway of alginate biosynthesis is generally divided into (i) synthesis of precursor substrate, (ii) polymerization and cytoplasmic membrane transfer, (iii) periplasmic transfer and modification, and (iv) export through the outer membrane. Bacterial alginate can be produced from Azotobacter and Pseudomonas. īacterial biosynthesis may provide alginate with more defined chemical structures and physical properties than can be obtained from seaweed-derived alginate. On a dry weight basis, the alginate contents are 22–30% for Ascophyllum nodosum and 25–44% for Laminaria digitata. After further purification and conversion, water-soluble sodium alginate power is produced. This alginate salt can be transformed into alginic acid by treatment with dilute HCl. The extract is filtered, and either sodium or calcium chloride is added to the filtrate in order to precipitate alginate. In this review, general properties of alginate and its current and potential applications in biomedical science and engineering will be discussed.Ĭommercially available alginate is typically extracted from brown algae ( Phaeophyceae), including Laminaria hyperborea, Laminaria digitata, Laminaria japonica, Ascophyllum nodosum, and Macrocystis pyrifera by treatment with aqueous alkali solutions, typically with NaOH. ![]() In this approach, hydrogels are used to deliver cells to the desired site, provide a space for new tissue formation, and control the structure and function of the engineered tissue. ![]() Tissue engineering aims to provide man-made tissue and organ replacements to patients who suffer the loss or failure of an organ or tissue. Alginate gels are also promising for cell transplantation in tissue engineering. In addition, alginate gels can be orally administrated or injected into the body in a minimally invasive manner, which allows extensive applications in the pharmaceutical arena. Drug molecules, from small chemical drugs to macromolecular proteins, can be released from alginate gels in a controlled manner, depending on the cross-linker types and cross-linking methods. Alginate wound dressings maintain a physiologically moist microenvironment, minimize bacterial infection at the wound site, and facilitate wound healing. Alginate hydrogels can be prepared by various cross-linking methods, and their structural similarity to extracellular matrices of living tissues allows wide applications in wound healing, delivery of bioactive agents such as small chemical drugs and proteins, and cell transplantation. The design of new biomaterials is now focused on mimicking many functions of the extracellular matrices of body tissues, as these can regulate host responses in a well-defined manner, and naturally-derived materials have recently been regaining much attention owing to their inherent biocompatibility.Īlginate is a naturally occurring anionic polymer typically obtained from brown seaweed, and has been extensively investigated and used for many biomedical applications, due to its biocompatibility, low toxicity, relatively low cost, and mild gelation by addition of divalent cations such as Ca 2+. The more recent evolution in this field has now led to the definition of a biomaterial as a material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body, and boundaries for the use of biomaterials are still expanding. Since the early twentieth century, however, these materials began to be replaced by synthetic polymers, ceramics, and metal alloys, due to their better performance and more reproducible properties, as compared to naturally derived materials. Materials derived from natural sources (e.g., wood) have a long history as biomaterials, and have often been used to replace tissues lost to disease or trauma (e.g., prosthetics). ![]() Biomaterials have traditionally been designed to be inert and not to interact with biological systems in the host.
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