Gellan Gum for Tissue Engineering Applications: A Mini Review
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2018, Vol 7, Issue 2
Abstract
Gellan gum-based hydrogels have been proposed for biomedical applications including bone repair and cartilaginous tissue regeneration. This polysaccharide has the ability to form stable gels without the use of harsh reagents and offers excellent gel stability and flexibility. Gellan gum can function as a minimally invasive injectable system, gelling inside the body in situ under physiological conditions and efficiently adapting to the defect site. This work presents an overview of the recent advances in the research on gellan gum for biomedical applications. Gellan gum (GG) is a polysaccharide produced by microbial fermentation of the Sphingomonas paucimobilis microorganism. GG is a linear anionic polysaccharide composed of tetrasaccharide (1,3-b-D-glucose, 1,4-b-Dglucuronic acid, 1,4-b-D-glucose, 1,4-a-L-rhamnose) repeating units, containing one carboxyl side group, and was initially described by Moorhouse et al. [1]. This material has a broad use in the food industry and biomedical fields, mostly due to its processing into transparent gels that are resistant to acid stress and exhibit excellent heat resistance up to 120 °C. It can be dissolved in water, and when heated and mixed with mono or divalent cations, forms a gel upon lowering the temperature under mild conditions. GG exists in two different forms: acetylated and deacetylated. Both form thermo reversible gels, varying in their mechanical properties, in fact the acetylated form produce soft and elastic gels, while the fully deacetylated polysaccharide yields hard and brittle gels. At high temperatures, GG is in the coil form; upon temperature decrease, a thermally reversible coil to double-helix transition occurs, which is a prerequisite for gel formation. Afterwards, a structure composed of anti-parallel double helices self-assembled to form oriented bundles, called junction zones, is formed. Untwined regions of polysaccharide chains, in the form of extended helical chains, link the junction zones, leading to the formation of a three-dimensional network, that creates the gel. The gelation process of GG solutions is strongly influenced by the chemical nature and amount of cations present in the solution. The presence of cations is of paramount importance when a structurally stable gel is to be prepared. In fact, at low GG concentrations, the helix formation and its partial aggregation may form an ordered structure, but this does not lead to gel formation because the number of helical aggregates does not give rise to a continuous network in the whole volume. The main barrier are the carboxyl side groups that repulse each other by electrostatic interaction, therefore hindering the tight binding of helices and their cohesive aggregation. The introduction of cations shields the electrostatic repulsion and thereby allows the tight binding and aggregation of helices. Furthermore, it is important to note that divalent cations promote the gelation much more strongly than monovalent ones. GG is commonly used in the food and pharmaceutical industry. However, it has been also proposed as new biomaterial for cartilage tissue engineering applications due to its versatility and efficacy for cartilage repair strategies involving both subchondral stimulation and cell transplantation. GG can be used also as drug delivery carrier, thus highlighting the versatility of this material. In fact, polymeric hydrogels represent ideal candidates for the design of sustained drug release platforms. Their high value relies on the tunable properties, such as swelling, porosity, mechanical stability and responsiveness to physical stimuli. All these factors can be precisely optimized to modulate the loading efficiency and the drug release kinetic.
Authors and Affiliations
R Spera, S Nobile, L Di Trapani
Keywords
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- EP ID EP592733
- DOI 10.26717/BJSTR.2018.07.001474
- Views 148
- Downloads 0
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