Abstract
A series of four different low molecular weight gellan gum products was obtained by alkaline hydrolysis with the aim to investigate the impact of the molecular weight on the rheological properties of the polysaccharide aqueous dispersions and on the physicochemical characteristics of derived ionotropic crosslinked hydrogels. In particular, thermo-rheological analysis was conducted on aqueous dispersions to study the influence of molecular weight on the thermogelation properties typical of the native polysaccharide while strain sweep experiments were conducted to establish if aqueous dispersion shows a viscoelastic behavior. The effect of different Ca2+ on the rheological properties of hydrogels were studied. Furthermore, ionotropic crosslinked hydrogels were analyzed in terms of morphology on the dried state and swelling behavior, while their viscoelastic properties were studied by means of rheological analysis conducted in frequency sweep regime after different time points of incubation in phosphate buffer at pH 7.4. Release experiments conducted using fluorescein isothiocyanate labelled dextran as a model diffusion agent and was performed to investigate the possibility of using the low molecular weight GG-derived hydrogels as an active molecule-releasing device. Finally, the cytocompatibility of hydrolysis products was investigated, as well as the capacity of hydrogels to encapsulate viable MC3T3-E1 preosteoblastic cells.
Highlights
Gellan Gum (GG) is a high molecular weight bacterial exopolysaccharide secreted by Pseudomonas elodea during aerobic fermentation
We aimed to investigate the influence of the molecular weight on the main physicochemical features of GG hydrogels
Basic hydrolysis is a well-known method used to reduce GG molecular weight in order to obtain derivatives that can be dispersed in water at relatively high concentrations without resulting in too viscous solutions, still maintaining ionotropic and thermos-rheological properties such as those of native GG
Summary
Gellan Gum (GG) is a high molecular weight bacterial exopolysaccharide secreted by Pseudomonas elodea during aerobic fermentation. It is an anionic polysaccharide composed of a tetrasaccharide repeating unit of one α-L-rhamnose (Rhap), one β-D-glucuronic acid (GlcpA) and two β-D-glucoses (Glcp) [1]. GG has been used as a thickener, gelling agent and stabilizer in many products of the food industry. Two types of GG have been mainly used for these purposes. The former is characterized by the presence of acyl substituents and is known as high-acyl, the second is called low acyl or deacetylated and is obtained by alkaline hydrolysis of HA Gellan Gum [4]
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