Physicochemical and Rheological Characterization of Different Low Molecular Weight Gellan Gum Products and Derived Ionotropic Crosslinked Hydrogels

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.

[Chemistry research on natural product derivatives of dihydro-β-agarofuran sesquiterpenoids]

Dihydro-β-agarofuran sesquiterpenoids possess chemical diversity and biodiversity. A dihydro-β-agarofuran sesquiterpenoid with only hydroxyl groups has been prepared by basic hydrolysis of crude extract of Euonymus bungeanus with 0.4% yield. Twelve derivatives were available in esterification, oxidation, decarboxylation, etc. Extensive ~1H-NMR,~(13)C-NMR, MS spectroscopic analyses and single-crystal X-ray diffraction analysis with Cu Kα radiation indicated that eleven derivatives were new compounds. The results will provide reference for chemistry study on natural product derivatives of dihydro-β-agarofuran sesquiterpenoids.