Molecular level and microstructural characterisation of thermally sensitive chitosan hydrogels

Abstract

Chitosan-glycerophosphate (GP) is a physiological pH solution at room temperature which forms a physical hydrogel upon heating to 37 C. The hydrogel is suitable for biomedical applications and in particular as a biodegradable scaffold for tissue engineering. Since the structure of the hydrogel is critical to cell-material interactions, small angle neutron scattering (SANS) and ultra SANS (USANS) were used to examine the molecular conformation of chitosan chains and the larger scale microstructure. On the nanoscale, the hydrogel is described in terms of a static component (characteristic length, X) which accounts for the physical cross-links, and a dynamic component (correlation length, x) which accounts for solution-like properties. Over the range 0.25-1.5 w/v% chitosan concentration the molecular structure is dependent on concentration with the characteristic length decreasing from $450

Investigation of gelation mechanism of an injectable hydrogel based on chitosan by rheological measurements for a drug delivery application

“…The correlation length at the spinodal temperature was calculated to be 46 nm, which is interestingly in the order of the hydrophobic domain dimensions recently investigated via the small angle neutron scattering (SANS) method. 55 The processes discussed above were concerned with the first and second regions in the temperature sweep graph of HV-HD2 sample shown in Fig. 1.…”

Water and polymer dynamics in a model polysaccharide hydrogel: the role of hydrophobic/hydrophilic balance

“…The detailed explanation of the structure and dynamics of hydrogel systems thus requires the combination of different and complementary physical methods suitable for the exploration of such different time and distance domains. [16][17][18][19] All these studies indicated that the balance between the hydrophilic/hydrophobic chemical groups and the degree of cross-linking of the polymer structure are key parameters which allow us to control the equilibrium swelling in hydrogels and their water-retaining ability, 20 thus providing the physicochemical bases for the design of efficient, smart hydrogelbased carriers and controlled release systems. 14,15 Additionally, rheology, NMR relaxometry measurements and neutron scattering experiments have been described in the literature as emerging methodologies used for the elucidation of the structural and viscoelastic properties of hydrogels.…”

“…14,15 Additionally, rheology, NMR relaxometry measurements and neutron scattering experiments have been described in the literature as emerging methodologies used for the elucidation of the structural and viscoelastic properties of hydrogels. [16][17][18][19] All these studies indicated that the balance between the hydrophilic/hydrophobic chemical groups and the degree of cross-linking of the polymer structure are key parameters which allow us to control the equilibrium swelling in hydrogels and their water-retaining ability, 20 thus providing the physicochemical bases for the design of efficient, smart hydrogelbased carriers and controlled release systems. 2 With this picture in mind, an extensive, multidisciplinary investigation has been carried out in the recent years on a paradigmatic model of chemically cross-linked polymers, namely cyclodextrin nanosponges (CDNS), with the main goal of understanding the state and the molecular environment of water molecules within the 3D polymeric network in the hydrogel state.…”

Synergistic interactions during thermosensitive chitosan-β-glycerophosphate hydrogel formation

“…[13][14][15][16][17] Whilst the application of the CS/b-GP system has been extensively studied, the understanding of its gelation mechanism is still controversial. 3,[18][19][20][21][22][23] Several interactions were proposed for the contribution to the gelation process of CS/b-GP by investigating its morphology, physicochemical and rheological properties, etc. The hydrophobic or water-structuring character of the glycerol moiety of b-GP was thought to be the main source of the heat-induced increase in hydrophobic attraction between CS molecules from the investigations on the effect of temperature 3,18,19 and urea 21 during the gelation process.…”