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      In-Depth Study into Polymeric Materials in Low-Density Gastroretentive Formulations

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          Abstract

          The extensive use of oral dosage forms for the treatment of diseases may be linked to deficient pharmacokinetic properties. In some cases the drug is barely soluble; in others, the rapid transit of the formulation through the gastrointestinal tract (GIT) makes it difficult to achieve therapeutic levels in the organism; moreover, some drugs must act locally due to a gastric pathology, but the time they remain in the stomach is short. The use of formulations capable of improving all these parameters, as well as increasing the resident time in the stomach, has been the target of numerous research works, with low-density systems being the most promising and widely explored, however, there is further scope to improve these systems. There are a vast variety of polymeric materials used in low-density gastroretentive systems and a number of methods to improve the bioavailability of the drugs. This works aims to expedite the development of breakthrough approaches by providing an in-depth understanding of the polymeric materials currently used, both natural and synthetic, their properties, advantages, and drawbacks.

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          Most cited references152

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          Biological interactions between polysaccharides and divalent cations: The egg-box model

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            Protein release from alginate matrices.

            W Gombotz (1998)
            There are a variety of both natural and synthetic polymeric systems that have been investigated for the controlled release of proteins. Many of the procedures employed to incorporate proteins into a polymeric matrix can be harsh and often cause denaturation of the active agent. Alginate, a naturally occurring biopolymer extracted from brown algae (kelp), has several unique properties that have enabled it to be used as a matrix for the entrapment and/or delivery of a variety of biological agents. Alginate polymers are a family of linear unbranched polysaccharides which contain varying amounts of 1,4'-linked beta-D-mannuronic acid and alpha-L-guluronic acid residues. The residues may vary widely in composition and sequence and are arranged in a pattern of blocks along the chain. Alginate can be ionically crosslinked by the addition of divalent cations in aqueous solution. The relatively mild gelation process has enabled not only proteins, but cells and DNA to be incorporated into alginate matrices with retention of full biological activity. Furthermore, by selection of the type of alginate and coating agent, the pore size, degradation rate, and ultimately release kinetics can be controlled. Gels of different morphologies can be prepared including large block matrices, large beads (>1 mm in diameter) and microbeads (<0.2 mm in diameter). In situ gelling systems have also been made by the application of alginate to the cornea, or on the surfaces of wounds. Alginate is a bioadhesive polymer which can be advantageous for the site specific delivery to mucosal tissues. All of these properties, in addition to the nonimmunogenicity of alginate, have led to an increased use of this polymer as a protein delivery system. This review will discuss the chemistry of alginate, its gelation mechanisms, and the physical properties of alginate gels. Emphasis will be placed on applications in which biomolecules have been incorporated into and released from alginate systems.
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              Carrageenans: Biological properties, chemical modifications and structural analysis – A review

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                Author and article information

                Journal
                Pharmaceutics
                Pharmaceutics
                pharmaceutics
                Pharmaceutics
                MDPI
                1999-4923
                07 July 2020
                July 2020
                : 12
                : 7
                : 636
                Affiliations
                Departamento de Química Orgánica y Farmacéutica, Facultad de Farmacia, Universidad de Sevilla, C/ Prof. García González, n.º 2, 41012 Seville, Spain; nievesiglesias@ 123456us.es (N.I.); elsa@ 123456us.es (E.G.); lrazogil@ 123456us.es (L.R.-A.); ebenito@ 123456us.es (E.B.); rlucas1@ 123456us.es (R.L.); graciagm@ 123456us.es (M.G.G.-M.)
                Author notes
                [* ]Correspondence: vdepaz@ 123456us.es
                Author information
                https://orcid.org/0000-0001-8521-2835
                https://orcid.org/0000-0002-8796-6873
                https://orcid.org/0000-0002-7171-5236
                https://orcid.org/0000-0002-6544-4732
                Article
                pharmaceutics-12-00636
                10.3390/pharmaceutics12070636
                7408198
                32645909
                0bfb07b1-a1ce-47eb-b1e9-3999a6ee52a1
                © 2020 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 12 May 2020
                : 03 July 2020
                Categories
                Review

                floating,low-density,grdds,raft systems,alginate,polysaccharides,cellulose,gums,carbopol,eudragit,gastroretentive

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