Glass Transition and Water Dynamics in Hyaluronic Acid Hydrogels

Abstract

, J.; A. Kyritsis; Monleón Pradas, M.; Vallés Lluch, A.; Gallego Ferrer, G.; P. Pissis (2013). Glass transition and water dynamics in hyaluronic acid hydrogels. Food Dielectric measurements contribute to the study of the molecular dynamics of water at biological interfaces, in the case of several biomolecules, such as polysaccharides [14] and hydrated proteins [15][16][17][18][19] and also in the case of synthetic hydrogels [20]. In the case of hydrated proteins, it has been shown that the observed dynamics depends strongly on the hydration level and a minimum amount of water is necessary for the onset of enzymatic activity in globular proteins [21]. The dynamics of water molecules in hydrated proteins which do not form a separate ice phase at subzero temperatures (uncrystallized water), has been extensively studied by dielectric measurements and a main secondary relaxation is recorded, attributed to water molecules in the hydration shell [16,17,19]. The main secondary relaxation of uncrystallized water exhibits similar characteristics in various hosting environments [22,23]. In the case of studies on hydrated proteins at low levels of hydration, the evolution of this main secondary dielectric relaxation of uncrystallized water with is not fully understood and it is believed to be highly connected to water dynamics.Theoretical studies suggest that the glass transition is driven by the translational reorientation of the hydrogen bonded network on the protein surface [33] and also connect the water-protein glass transition to the denaturation of the globular proteins, suggesting that both correspond to energetic sub-states, while an energy criterion for the onset of mobility of strong protein-water bonds is induced [34]. In the case of globular proteins the observed dielectric relaxation associated to the calorimetric glass transition has been attributed in literature to a combined motion of uncrystallized water molecules in the protein hydration shell and segments of the protein surface [19,24,25,30]. Measurements in synthetic hydrogels based on poly(hydroxyl ethyl acrylate) (PHEA) by dielectric and other experimental techniques showed that the segmental α relaxation (dynamic glass transition) is significantly plasticized by water [20]. In addition, correlations were observed between results on the organization of water in the hydrogels and on water effects on polymer dynamics. In particular, distinct changes in the dielectric response at the water content of the completion of the first hydration layer indicated that water molecules themselves contribute to the dielectric response at higher water contents [20]. Despite the extended use of HA hydrogels in biological applications, the dielectric behavior of such materials at low water concentrations and subzero temperatures has not been studied so far in detail. In the existing literature dielectric results refer mainly to dilute aqueous solutions of HA salts and particularly at room temperature, using time-domain dielectric measurements [35]. The present study pr...

Formulation and Characterization of Native and Crosslinked Hyaluronic Acid Microspheres for Dermal Delivery of Sodium Ascorbyl Phosphate: A Comparative Study

“…On the one hand, this suggested that SAP was not reversible in terms of humidity sorption/desorption, and that water molecules were not easily detached from it, perhaps because of their condensation among the hydrophobic skeleton of the drug. On the other hand, MS formulations (panels (b) and (c)) showed, as previously observed for native HA [67,68], similar trends for their sorption and desorption ramps, and high water-binding capacity due to H-bonds and electrostatic interaction with hyaluronan hydroxyl and carboxylic groups, respectively. Two-stages moisture sorption processes occurred for hyaluronan MS formulations, and this was in agreement with data already reported in the literature for native HA [67,68].…”

“…On the other hand, MS formulations (panels (b) and (c)) showed, as previously observed for native HA [67,68], similar trends for their sorption and desorption ramps, and high water-binding capacity due to H-bonds and electrostatic interaction with hyaluronan hydroxyl and carboxylic groups, respectively. Two-stages moisture sorption processes occurred for hyaluronan MS formulations, and this was in agreement with data already reported in the literature for native HA [67,68]. Indeed, in response to RH increment from 0 to 60%, water uptake slowly increased up to 20.9% for HA MS, 14.2% for HA–SAP MS, 16.4% for HA-CL MS, 23.0% for HA-CL–SAP MS (changes in mass similar to that of SAP (+ 17.8%) at 60% RH).…”

Bleached extruder chemi‐mechanical pulp fiber‐PLA composites: Comparison of mechanical, thermal, and rheological properties with those of wood flour‐PLA bio‐composites

“…However, the T g values of both of the WF and PF composites decreased slightly when the fiber content increased from 10% to 40%. This is probably because of the presence of a low fraction of cellulose fibers that contain polar groups (such as hydroxyl groups), and the electrostatic repulsion between these polar groups increased the distance between molecular chains and resulted in a decrease in T g . The crystallinity values ( X c ) of the WF and PF composites increased compared to that of the PLA matrix (Table ).…”

Characterization of bound water in skin hydrators prepared with and without a 3D3P interpenetrating polymer network

“…The water content from topical humectants can quickly evaporate from the warm skin surface, depending on the influence of RH and temperature, leaving a dehydrated product film along with HA and other nonvolatile ingredients. Others have pursued improving topical humectant performance by modifying HA through covalently bonded cross‐linking structures and covalently bonded hydrophobic modifications (e.g., AcHA) . Although these altered forms of HA do offer superior hydration benefits compared to traditional linear HA, they do not combine both properties of improved water binding by cross‐linking with improved affinity to the skin's surface through hydrophobic modifications.…”

“…Others have pursued improving topical humectant performance by modifying HA through covalently bonded cross-linking structures and covalently bonded hydrophobic modifications (e.g., AcHA). 19,20,22,23,34,35 Although these altered forms of HA do offer superior hydration benefits compared to traditional linear HA, they do not combine both properties of improved water binding by cross-linking with improved affinity to the skin's surface through hydrophobic modifications. However, we theorized water and binding water more tightly in comparison to the commercial HA-containing benchmark.…”