No abstract

A highly stretchable hyaluronic acid (HA)/sodium alginate (SA) hydrogel was developed in this study based on an interpenetrating polymer network. HA/SA hydrogels were prepared by mixing two polysaccharides followed by covalent crosslinking via epoxy groups on HA molecules and ionic crosslinking via divalent ions on SA chains sequentially. The effect of HA/SA ratio on the pore size and distribution, swelling ratio, elongation and rheological properties as well as protein loading and release properties of HA/SA hydrogels was explored. Moreover, a surface modification method, layer-by-layer (LBL) assembly technique, was applied to modify the hydrogel to evaluate the hydrogel's tenability in varying biological performance. It was then shown that the hydrogels had the pore sizes ranging from 100 to 50 μm. With the increase in SA content of the resulting hydrogels, the pore size, swelling ratio, and storage modulus (G') and loss modulus (G″) of the hydrogel all decreased, whereas the in vitro bulk weight loss was fastened. Moreover, elongation at break (EB) value increased first, reached a peak value and then decreased, that is HA8/SA1 (HA:SA = 8:1) had the highest EB value of 417%. This hydrogel could retain 33.2% of the pre-loaded protein even after 72 h, which could be further attenuated when LBL was used to shell the hydrogel. The growth of fibroblasts on HA8/SA1 hydrogel gave preliminary assessment on its suitability as a cellular carrier, while the LBL modified HA8/SA1 hydrogel also favored the anchoring of keratinocytes, further enhancing its cell carrier role for tissue regeneration, especially skin engineering.

The density and the heat capacity at saturation vapor pressure of isoamyl dl-lactate were measured at a temperature range of 288.15–453.65 K using a capillary pycnometer and adiabatic calorimeter, respectively. The Antoine equation was used to correlate the vapor pressure data which was determined with an ebulliometric technique at a temperature range of 374.59–478.56 K, and the deviation between the calculated value and the experimental data was less than 0.87%. On the basis of the Clausius–Clapeyron equation, the vaporization enthalpy of isoamyl dl-lactate at atmospheric pressure boiling point (T b, 474.89 K) was calculated to be 43.27 kJ/mol. According to the Othmer’s method, the standard vaporization enthalpy, Δvap H (298.15 K) was estimated using octanol and heptanol as reference substances, and the results are 57.21 and 57.35 kJ/mol, respectively.

The esterification reaction between isoamyl alcohol and lactic acid was studied over silica gel-supported sodium hydrogen sulphate (NaHSO 4 Á Silica). The influences of the external mass transfer, internal mass transfer, reaction temperature, catalyst loading, and initial reactant molar ratio were investigated. Kinetic experimental data of this esterification reaction obtained at different temperatures (343-378 K) were correlated with three models (the pseudo-homogeneous (PH), Eley-Rideal (ER), and Langmuir-Hinshelwood (LH) model). The UNIFAC method was employed to estimate the activity coefficients when the non-ideal thermodynamic behaviour of the reaction mixture was considered. The results show that the ER model is more appropriate for predicting the dynamic data of an esterification reaction. It was found that water and isoamyl alcohol were more strongly adsorbed onto the surface of NaHSO 4 Á Silica than lactic acid and isoamyl lactate, by comparing the adsorption equilibrium constants of different components existing in the reaction. The activation energy and standard enthalpy of the reaction were found to be 54.1 and À6.27 kJ mol À1 , respectively.

No abstract