Recent progress in gellan gum hydrogels provided by functionalization strategies

Abstract

Gellan gum, a microbial exopolysaccharide fermentation product of Pseudomonas elodea, is a natural biomaterial that has shown promise for tissue engineering and regenerative medicine applications. Although this exopolysaccharide possesses many advantages, such interesting physicochemical properties and non-cytotoxicity, the mechanical properties and processability of gellan gum are not totally satisfactory in different tissue engineering contexts, i.e. gellan gum hydrogels are mechanically weak and the high gelling temperature is also unfavourable. An additional critical limitation is the lack of specific attachment sites for anchorage-dependent cells. However, the multiple hydroxyl groups and the free carboxyl per repeating unit of gellan gum can be used for chemical modification and functionalization in order to optimize its physicochemical and biological properties. A number of physical modification approaches have also been employed. This review outlines the recent progresses for gellan gum hydrogels and derivatives, and identifies the new challenges in tissue engineering, provided by blending and/or chemical modifications. Figure 2 -(A) Gradual transformation of gellan gum in aqueous solutions: (1) due to a change in temperature, the transition of a thermally reversible coil to double-helix chain occurs (coil-helix transition). Then, the helices self-assemble in clusters joined together by the untwined polysaccharide regions; (2) ionic-crosslinking: polymer backbone carrying the charge bind with cations (blue circles); (3) chemical crosslinking: covalent bond between polymer chains. (B) Photographs of 2% (w/v) HAGG and LAGG hydrogels.The described properties have been supporting the exploitation of gellan gum for different tissue engineering (TE) and regenerative medicine applications 13,16 . Both acellular and cellular strategies using GG were successfully proposed for drug delivery 17-20 , cartilage 21, 22 and intervertebral disc repair 23,24 . Further attractive characteristics of gellan for TE are its biocompatibility, non-cytotoxicity, mild conditions of processing, structural similarity with native glycosaminoglycans (due to the presence of glucuronic bioprinted structures that consist of discrete layers of primary cortical neurons encapsulated in GG-RGD hydrogels. These gellan gum-based brain-like structures provide an opportunity to mimic more accurately in in vitro studies the 3D microstructure of neuronal tissues.The permeability of cells from GG hydrogels is crucial for cell culture and for cell survival. GG-based hydrogels present different permeability to cells. The chick embryo chorioallantoic membrane (CAM) assay performed by in GG, iGG-MA and phGG-MA hydrogels showed that the hydrogels present different permeability to cells. iGG-MA and phGG-MA hydrogels are non-permissive to endothelial cells ingrowth, behaviour not observed in the unmodified GG hydrogels. The results showed that the methacrylation of GG allowed tuning the hydrogel permeability to cells. Conclusions and final remarksGellan ...

Recent trends and applications of polysaccharides for microencapsulation of probiotics

“…Gellan gum is an extracellular polysaccharide produced by bacterium Sphingomonas elodea using a fermentative process through immersion method (Osmałek et al., 2017). Structurally, gellan gum is a linear polysaccharide composed of a four‐unit structure including glucose, glucuronic acid, and rhamnose with a molar ratio of 2:1:1 (Bacelar, Silva‐Correia, Oliveira, & Reis, 2016). The most important functionalities of gellan gum applied in probiotic microencapsulation are that it can hold small particles in suspension without increasing the viscosity significantly, not easily be degraded by the action of enzymes, and resistance to acidic environments (Wang, Wen, & Bai, 2016).…”

Biological Role of Gellan Gum in Improving Scaffold Drug Delivery, Cell Adhesion Properties for Tissue Engineering Applications

“…Deacylated GG is the most commonly used in the tissue engineering (TE) and pharmaceutical fields [3], because of their relative ease of isolation and processing methodology. The GG average molecular weight is about 500 kDa [4]. GG is commercially available under the trade name Gelrite TM (acyl GG or acylated GG) and Kelcogel TM (low acyl GG or deacylated GG) [5][6][7][8].…”

“…Major routes for preparing gellan gum-based biomaterials[4,32,[34][35][36][37][38][39][65][66][67][68][69].…”

Evaluation of double network hydrogel of poloxamer-heparin/gellan gum for bone marrow stem cells delivery carrier

“…Recently, an interest of gellan gum (GG) has been generated due to its various advantages in pharmaceutical and biomedical applications [9,10]. GG hydrogel can transform from a coiled form to a double-helix structure when exposed to high (˜90°C for a 1% solution) to low temperature [10]. This property provides soft and elastic gels to hard and rigid gels depending on the amount of GG.…”

“…Despite its many advantages in tissue engineering, GG hydrogel fails to meet the conditions of cell vehicle because of its too high gelation temperature for cell encapsulation. Another challenge which limits the application of GG hydrogel is lack of moieties for ligand binding [10]. Several reports lowered gelation temperature of GG hydrogel by chemically scissoring or carboxymethylation and thiolation of the backbone of GG hydrogel.…”