Nanofibrous material from hyaluronan derivatives preserving fibrous structure in aqueous environment.

Nanofibrous materials produced from natural polymers have wide range of potential uses in regenerative medicine. This paper focuses on preparation of nanofibrous layers produced from intentionally hydrophobized derivatives of hyaluronan, which is known for its ability to promote wound healing. This structural modification of hyaluronan expands the range of potential uses of this promising material, which is otherwise limited due to the hydrophilic nature of hyaluronic acid. The aim of this research was preparation of nanofibrous material that would retain its fibrous structure and dimensional stability even after getting into contact with an aqueous medium, which is impossible to achieve with layers composed solely of native hyaluronan. As a result, such material would be able to retain its breathability and good mechanical properties when both dry and wet. Furthermore, all prepared materials were proved non-toxic for cells. This self-supporting nanofibrous matrix can be used as a scaffold, or porous wound dressing.

Seasonal variations in the skin parameters of Caucasian women from Central Europe.

BACKGROUND: The human skin is greatly affected by external factors such as UV radiation (UVR), ambient temperature (T), and air humidity. These factors oscillate during the year giving rise to the seasonal variations in the skin properties. The aim of this study was to evaluate the effect of seasons, environmental T, relative and absolute humidity on the skin parameters of Caucasian women, perform a literature review and discuss the possible factors lying behind the found changes. MATERIALS AND METHODS: We measured stratum corneum (SC) hydration, transepidermal water loss (TEWL), sebum level, erythema index, and elasticity parameters R2 and R7 on the forehead and the cheek of Caucasian women from the Czech Republic throughout the year. We also performed a non-systematic literature review focused on the seasonal variations in these skin parameters. RESULTS: We confirmed a well-documented low SC hydration and sebum production in winter. In spring, we found the lowest TEWL (on the forehead) and the highest SC hydration but also the highest erythema index and the lowest elasticity presumably indicating skin photodamage. For most of the skin parameters, the seasonal variations probably arise due to a complex action of different factors as we extensively discussed. CONCLUSION: The data about the seasonal variations in the skin parameters are still highly inconsistent and further studies are needed for better understanding of the normal skin changes throughout the year.

Multiwavelength UV-metric and pH-metric determination of the multiple dissociation constants of the lesinurad.

Potentiometric and spectrophotometric pH-titrations of the lesinurad for three consecutive dissociation constants determination were compared. Lesinurad is a selective inhibitor of uric acid reabsorption as part of a combination of medicines to treat high levels of uric acid in blood, also called hyperuricemia. Nonlinear regression of the pH-spectra with REACTLAB and SQUAD84 and of the pH-titration curve with ESAB determined three multiple close dissociation constants. The protonation scheme of lesinurad was suggested. A sparingly soluble anion L- of lesinurad was protonated to the still soluble species LH, LH2+ and LH32+ in pure water. Three consecutive thermodynamic dissociation constants were estimated pKTa1 = 2.09, pKTa2 = 4.25, pKTa3 = 6.58 at 25 °C and pKTa1 = 1.96, pKTa2 = 4.16, pKTa3 = 6.32 at 37 °C by UV-metric spectra analysis. The graph of molar absorption coefficients shows that the spectrum of species LH2+ and LH vary in colour, while protonation of chromophore LH2+ to LH32+ has less influence on chromophores in the lesinurad molecule. Three multiple thermodynamic dissociation constants of 1 × 10-4 M lesinurad were determined by the pH-metric analysis pKTa1 = 2.39, pKTa2 = 3.47, pKTa3 = 6.17 at 25 °C and pKTa1 = 2.08, pKTa2 = 3.29, pKTa3 = 6.03 at 37 °C. The values of enthalpy ΔH0(pKa1) = 19.19 kJ mol-1, ΔH0(pKa2) = 13.29 kJ mol-1, ΔH0(pKa3) = 38.39 kJ mol-1, show the dissociation process is endothermic. The positive values of ΔG0(pKa1) = 11.93 kJ mol-1, ΔG0(pKa2) = 24.26 kJ mol-1, ΔG0(pKa3) = 37.56 kJ mol-1 at 25 °C indicate that the dissociation process of pKa2 is not spontaneous, which was confirmed by its value of entropy ΔS0(pKa1) = 24.37 J mol-1, ΔS0(pKa2) = -36.79 J mol-1, ΔS0(pKa3) = 2.79 J mol-1. Three macro-dissociation constants of lesinurad and protonation locations were predicted by MARVIN and ACD/Percepta.