Natural polymers alginate

For many years, in most cases synthetic polyelectrolytes such as PDADMAC or PEI as PC, and PAC, PAMPS, or PSS as PA were used for complex formation. But at present, the application of so-called natural polymers is of growing importance in the field of complex formation. Natural polymers occur in nature and can be extracted. Examples are chitosan as well as polysaccharides such as starch, pectin, or alginate. Natural polymers are used because of their good biodegradability and high biocompatibility in a wide range of applications in industry. They can have cationic charge (chitosan) [137] or can be modified with cationic as well as hydro-phobic units [74]. 

When acidic and basic polymeric polyelectrolytes are mixed, they form a complex which precipitates. Based on this, mammalian cells are coated with sodium alginate (natural polymer) solution (in water) and then put in a suitable water-soluble acrylate solution. This forms a hard encapsulation around the mammalian cell this is impervious to antibodies. Suggest a suitable acrylate (as methacrylate) for the encapsulation. 

Besides the previously mentioned collagen, a wide variety of natural polymers have been involved in the synthesis of bio-nanohybrid materials with potential application in bone repair and dental prostheses. For instance, some recent examples refer to bionanocomposites based on the combination of HAP with alginate [96,97], chitosan [98,99], bovine serum albumin (BSA) [100], sodium caseinate [101], hyaluronic acid [102], silk fibroin [103,104], silk sericin [105], or polylactic add (PLA) [106,107]. These examples illustrate the increasing interest in the subject of HAP-based biohybrid materials, which has led to almost 400 articles appeared in scientific journals in 2006 alone. 

There are several reports on the coating of bone-like hydroxyapatite onto natural polymer substrates. Kawashita et at. [57] reported that carboxymethylated chitin and gellan gum gels, which have carboxyl groups, can form hydroxyapatite on their surfaces in SBF if they are treated with a saturated Ca(OH)2 solution in advance, while curdlan gel, which has no carboxyl group, does not form hydroxyapatite in SBF, even if it is treated with Ca(OH)2 solution. These results support the hypothesis that carboxyl groups induce hydroxyapatite nucleation. Kokubo et at. [58,59] reported that non-woven fabrics of carboxymethylated chitin and alginate fibers also form hydroxyapatite on their surfaces in SBF if they are treated with Ca(OH)2 solution. 

Ionic cross-linking can be achieved in a number of systems and different microstructures result. For rigid chains it is possible for the ion to coordinate in a specific manner with the chain. Alginates are a good example of this. These are natural polymers derived from a brown macro-algae. The method of extraction and the species of the algae influences the chemistry and hence the rheology of these polymers. There... 

The selective dense layer of hydrophilic membranes is made from different polymers with a high affinity for water. These polymers contain ions, oxygen functions like hydroxyl, ester, ether or carboxylic moieties, or nitrogen as imino or imi-do groups. Preferred hydropilic polymers are polyvinylalcohol (PVA) [32], poly-imides, cellulose acetate (CA) or natural polymers like chitosan [33] or alginates. Organophilic membranes usually consist of crosslinked silicones, mostly polydimethyl siloxane (PDMS) or polymethyl octyl siloxane (POMS). 

Biodegradable polymers, both synthetic and natural, have gained more attention as carriers because of their biocompatibility and biodegradability and therewith the low impact on the environment. Examples of biodegradable polymers are synthetic polymers, such as polyesters, poly(orfho-esters), polyanhydrides and polyphosphazenes, and natural polymers, like polysaccharides such as chitosan, hyaluronic acid and alginates. 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

Natural polymers polysaccharides (celullose, starch, pectins, dextrans, agar, agarose, alginate, chitine, chitosan, etc.) and fibrous proteins (collagen, keratine, etc.). 

The most common method for enzyme entrapment is by polymerizing acrylamide in the presence of the enzyme. The result is a flexible porous polymeric gel, which traps the enzyme but allows the diffusion of substrates and products (Figure 5.11). Whole cells are also similarly entrapped in alginate, a natural polymer which occurs in... 

In this experiment you will work with a natural polymer called alginic acid that comes from seaweed. Alginic acid is a polysaccharide as are cellulose and starch. Unlike cellulose and starch, however alginic acid as the name implies contains acidic functional groups called carboxylic acids. Salts of alginic acid are used as food additives, especially as a thickener. 

Natural polymers extracted and purified from plant and animal sources often vary significantly in their purity. For example, alginate is available in over 200 different... 

Transformations with immobilized enzymes or cells Often the stability of the biocatalyst can be increased by immobilization and many different enzymes and cells have been immobilized by a variety of different methods. The most popular method for the fixation of whole cells is entrapment or encapsulation with calcium alginate. Other natural gels e.g., carrageenan, collagen, chemically-modified natural polymers e.g., cellulose acetate and synthetic gels and polymers e.g., polyacrylamide or polyhydroxyethylmethacrylate can also be used for this type of immobilization. 

The materials used to make the impressions for dentures, crowns, or bridges are almost always polymeric. Natural polymers, such as agar-agar (a polygalactan) or alginates, have been used in this application for many years, but more recently various polysulfides. 

Synthetic fibres, manufactured fibres can be divided into those derived from natural polymers (such as regenerated protein fibres rayon, cellulose acetates, or alginates) and those derived from synthetic polymers including nylons, polyesters, acrylics, and polyolefins. 

Natural polymer originated compounds can be applied as stabilizers of nanoclusters. Highly stable silver nanoparticles have been successfully synthesized by gamma ray irradiation in the presence of sodium alginate (Liu et al. 2009) or chitosan (Chen et al. 2007). 

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