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Macroalgal Fucoidan for Biomedical Applications
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Jayachandran Venkatesan, Sukumaran Anil, Sneha Rao, Se-Kwon Kim
For fucoidan isolation from seaweed, dry material is finely powered through either pulverisation to get the micrometer size particulate matter. Further, sufficient amount of ethanol should be added into the seaweed powder to remove the pigments, proteins and other dust particles. Subsequently, seaweed power is washed with acetone and centrifuged and dried. A small amount of seaweed (approximately 5g) is treated with 100 ml of distilled water and stirred for an hour, and this process can be repeated two to three times to extract the maximum amount of fucoidan. The fractions are combined and centrifuged, and the supernatant treated with 1% (W/V)CaCl2 solution to get the alginate precipitation. Further, the complete solution is kept overnight at 4°C for total alginic acid precipitation, followed by centrifugation to spate the alginate (Rani et al., 2017; Yang et al., 2008). To get the fucoidan, the solution is mixed firstly with 30% ethanol and kept for 4 h at 4°C and centrifuged to remove the impurities. The supernatant is made to 70% of ethanol to precipitate the fucoidan and placed at 4°C overnight for total yield. Precipitated fucoidan solution is centrifuged and washed with ethanol and acetone to get the crude fucoidan and dried at room temperature (Rani et al., 2017). Figure 2.1 (A) shows the similar isolation procedure while Synytsya et al. (2010) have used mild acid (HCl) for the isolation of fucoidan. The yield of fucoidan is calculated as follows,
Therapeutic Uses of Phycocolloids
Published in Leonel Pereira, Therapeutic and Nutritional Uses of Algae, 2018
Alginic acid is present in the cell walls of brown seaweeds, where it is partially responsible for their flexibility (McHugh 2003). Alginic acid was discovered in 1883 by E.C.C. Stanford, a British pharmacist, who called it algin. Alginic acid is extracted as a mixed salt of sodium and/or potassium, calcium, and magnesium. Since Stanford discovered algin, the name has been applied to a number of substances, e.g., alginic acid and all alginates derived from alginic acid. The extraction process is based on the conversion of an insoluble mixture of alginic acid salts of the cell wall in a soluble salt (alginate) which is appropriate for the water extraction (Lobban et al. 1988, Lahaye 2001).
Marine Biopolymers
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Alginate can be used in drug delivery under different forms as tablets, capsule, hydrogels, films, or nanofibers. The simple way used sodium alginate as an excipient that is mixed into a drug and pressed into tablet. When going through the gastrointestinal (GI) tract, the tablet will absorb the water in the stomach at a low pH (pH = 1.2 to 2), swells, transforms to alginic acid gel and then releases the drugs. After that when the tablet moves to the intestine, the pH will increase to 6.5 to 7. With the high Na+ concentration in the GI tract, the alginic acid will exchange ions and return the sodium alginate and dissolve. This process depends on many factors such as the MW of alginate, the M/G ratio, the particle size, the ratio of alginate/drug, and the porosity of the tablet. Liew et al. have carried out the impressive examination on the influence of these factors on the release of chlorpheniramine maleate from sodium alginate excipient tablet. The result showed that in low pH, the small sodium alginate particles rehydrated faster than the large particles, transformed to acid gel, and reduce the burst release. The alginate with high mannuronate slows down the release better than high guluronate. The high concentration of alginate also controls the release better than low concentration. In general, the alginate excipient can keep the release of drug within eight hours (Liew et al., 2006). The influence of various grades of alginate (with different M/G ratio, size and viscosity), sodium/calcium alginate and ammonium/calcium alginate, pH of medium on swelling, erosion and drug (metronidazole) and release from alginate-based matrix tablets were investigated in the study of Sriamornsak et al. The influence of the M/G ratio of sodium alginate is different depending on the pH. The high M alginate tablet released the drug faster in a buffer of pH 6.8 than in pH 1.2, while the high G alginate tablet delivered drug faster in acid solution with pH 1.2 and slowest in pH 6.8. Especially, the two mixtures of salt alginate, sodium/calcium alginate and ammonium/calcium alginate, were disintegrated very quickly in pH 1.2, released up to 90% in 30 minutes (Sriamornsak et al., 2007). Beside the solid form in tablet drug, alginate can be prepared under hydrogel, film, sponge, and scaffold forms that can contain and release the drugs in different applications in medicine as discussed in the next sections.
Alginate-based matrix tablets for drug delivery
Published in Expert Opinion on Drug Delivery, 2023
Natalia Veronica, Paul Wan Sia Heng, Celine Valeria Liew
Alginate-based matrix tablets prolong drug release through the formation of a gelatinous barrier layer upon hydration that impedes drug release. By utilizing the gelling property of alginate, formulations that can maintain drug release from 6 h up to 16 h have been developed [35,37,43]. Alginates demonstrate pH-dependent hydration due to the presence of mannuronic acid (pKa 3.38) and guluronic acid (pKa 3.65) [1]. At a pH milieu below the pKa, alginate converts to alginic acid, which can swell on hydration but is insoluble. Hodsdon et al. [46] reported that a continuous, viscous gel layer was formed in neutral pH, whereas a tough, rubbery, and porous gel layer was formed in acidic pH. These differences in the gel layer morphology and polymer hydration are thought to be responsible for the differences in the drug release behavior in neutral and acidic pH dissolution medium.
Fibronectin modified alginate coating enhances cell targeting and homing to bone marrow in BALB/c mice
Published in Journal of Microencapsulation, 2022
Yogesh Kumar Verma, Gangenahalli Ugraiah Gurudutta
The A-F conjugate was found to significantly coat cells within 20 min of incubation without showing any cytotoxicity. The conjugate was not internalised by cell up to 48 h of coating, which is sufficient time for transfused stem cells to reach BM (www.cancer.net). This would also not interfere with the cellular homeostasis of stem cells and maintain primitiveness of cells. Upon reaching to BM endothelium, due to high concentration of secreted fibronectin from BM stromal cells, the A-F coat would be removed from the cell surface. In addition, the secreted MMPs from many organs also help in clearing of Fibronectin. To completely remove the alginate coat from blood stream after deshielding, we have used ascorbic acid mediated oxidative degradation of alginate. In vitro, complete alginate capsules degradation was observed within 96 h of incubation, therefore alginic acid supplementation was given to mice for 4–5 days after infusion of A-F-coated cells. Ascorbic acid having pH 3.5 also acts as antimicrobial and confers protection against infections (Tajkarimi and Ibrahim 2011).
Development and pharmacokinetic evaluation of alginate-pectin polymeric rafts forming tablets using box behnken design
Published in Drug Development and Industrial Pharmacy, 2018
The advancement of new materials built on polysaccharides is due to their benefits as low cost, freely available, biodegradable, nontoxic and sustainability. Biopolymers such as sodium alginate, pectin and numerous others have been used in the field of GRDDs. Sodium alginate, the sodium salt of alginic acid, is a biodegradable nontoxic naturally occurring macromolecule hydrate and swells in water, but in acidic environment it produces gel after protonation [7,8]. Sodium alginate is a pH sensitive polymer stable at acidic pH, but unstable in alkaline medium because at higher pH, a rapid dissolution occurs that limits its application and can be crosslinked by physical and chemical mechanisms. Mono and divalent cations (sodium and calcium) can be used for crosslinking of sodium alginate to form three-dimensional gel network [9,10]. Pectin, a naturally occurring polysaccharide present in the cell wall of plants, is made by uronic acid residues linked through α-1, 4-glycosidic bond. Carboxyl groups of pectin rapidly form viscous gel upon contact with gastric fluid in the presence of divalent cations. Hydroxypropyl methyl cellulose K100M (HPMC K100M), a hydrophilic polymer, sustained the release of drug by enhancing the viscosity of gel layer. HPMC K100M releases the drug from gel barrier by diffusion process [11].