Algae Biomass: Characteristics and Applications by Katarzyna Chojnacka Piotr Pawel Wieczorek Grzegorz Schroeder & Izabela Michalak

Author:Katarzyna Chojnacka, Piotr Pawel Wieczorek, Grzegorz Schroeder & Izabela Michalak
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

7.3.1.1 Alginates

Alginates are a group of anionic copolymers isolated mainly from brown algae and, in particular, from species such as Laminaria hyperborea, Laminaria digitata, Laminaria japonica, Ascophyllum nodosum, and Macrocystis pyrifera, representing 17–45% of the algal dry weight (George and Abraham 2006; Vera et al. 2011; Goh et al. 2012; Kraan 2012; Lee and Mooney 2012). Alginates have the ability to create gels that are responsible for the mechanical and structural features enabling the flexibility and participation in the ion exchange of brown seaweeds (Silva et al. 2012a). These biopolymers have a number of important advantages, including the fact that hydrogels form under mild conditions of pH and temperature and are biodegradable, biocompatible, cheap, nontoxic, and susceptible to sterilization and storage (Mayakrishnan et al. 2013). Many articles have reported that alginates mainly have an antioxidant effect, and their biological activity depends on the molecular weight and content of the anionic groups. The unique properties of alginates and their biological activity can be adapted to many applications (Ahmed et al. 2014).

Alginates are valuable and important polysaccharides, as they can be applied to the engineering and the regeneration of almost all tissues. In the form of injection hydrogel, they are being used to encapsulate and deliver bubbles ovarian follicle maturation, islets of Langerhans and stem cells. Alginate hydrogel has been tested in nerve tissue engineering, bone tissue engineering and cartilage, intervertebral disks, and the regeneration of skeletal muscle. In conjunction with poly(ethylene glycol) molecules and antibodies, it participates in the capture of intraepithelial human blood progenitor cells, while, when associated with hydroxyapatite, it takes part in the regeneration of the bone interface. As a porous skeleton, it creates deposits of capillaries in tissues, and as a nanofiber skeleton, it is used in engineering skin tissue and building blood vessel replacements. It also plays an important role in cardiac tissue engineering (Bačáková et al. 2014). Alginates are present in the pharmaceutical industry as useful encapsulate matrices and drug carriers. In addition, when included in oral tablets, they can improve the bioadhesive properties of said tablets (Goh et al. 2012). The ability of alginic acid to bind divalent metal causes the heavy metals to be gelled by alginic acid, and consequently, they become insoluble in the intestine and cannot be absorbed into the body tissue. Therefore, both it and its derivatives are used in the treatment of gastritis and as antiulcer substances. Examples of such drugs containing alginates are “Gaviscon,” “Algitec,” and “Gastralgin.” Besides, alginates have an antitoxic effect on hepatitis through the normalizing of lipid and glycogen in the liver, an example of such a drug being “Detoxal” (Kraan 2012). Alginate hydrogels show a structural resemblance to the extracellular matrix of the living tissue, so that they play an important role in the process of wound healing/dressing, delivery of bioactive substances, and transplantation of cells. Due to their adsorbent and hemostatic properties, they have many uses in the protection of wounds. Alginate-based wound dressings have many advantages, like the support of granulation tissue formation, swift epithelialization, and healing.

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