Skin aging causes changes such as wrinkles and flaccidity leading to a large demand for aesthetic procedures, including dermal filling. A key agent in dermal filling is hyaluronic acid (HA), which is a naturally occurring glycosaminoglycan. However, it is a hydrophilic macromolecule that experiences great difficulty in crossing the skin barrier causing most commercial formulations containing it to be injectable, which in turn brings risks since they involve an invasive technique. In that sense, the aim of this study was to develop and characterize nanoparticles obtained from ionic interaction between HA and lysine (Lys) for use as a potential agent of dermal filling for topical application, increasing and improving its applicability and safety. To this end, nanoparticles were obtained by dripping of Lys over HA under magnetic stirring. A nanometric size was confirmed and a suitable surface charge was obtained by zeta potential. Nanoparticles were almost spherical in shape with a smooth surface. Interaction between raw materials for preparing nanoparticles was studied by FTIR and NMR spectroscopy and an ionic interaction was confirmed. These physicochemical features suggest that obtained nanoparticles can be further used as a topical dermal filling.Uniterms: Nanotechnology. Skin aging/non-invasive method. Skin aging/treatment/study.

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The solvent dependence of the 1H, 13C and 15N NMR spectra of (E)‐fluoroacetoxime [(E)‐FAO] and of (E)‐fluoroacetoxime O‐methyl ether [(E)‐FAOME], was examined and the HF, CF and NF couplings are reported. Density functional theory (DFT) at the B3LYP/6–311++g(2df,2p) level with ZPE (zero point energy) correction was used to obtain the rotamer geometries. In both (E)‐FAO and (E)‐FAOME the DFT method gave two energy minima corresponding to the cis (F—C—CN, 0°) and gauche (F—C—CN, 124.1°) rotamers. In contrast, in (Z)‐FAO the DFT method gave only one energy minimum corrsponding to the trans rotamer. The 4JHF and 1JCF couplings in (E)‐FAO were analyzed by solvation theory assuming the cis and gauche forms to give $E_{cis}-E_{gauche} = 3.3 \, {\rm kcal\, mol}^{-1}$ in the vapor phase, decreasing to 1.54 kcal mol−1 in CCl4 and −1.19 kcal mol−1 in DMSO (1 kcal=4.184 kJ. In (E)‐FAOME the observed couplings, when analysed similarly by solvation theory, gave $E_{cis}-E_{gauche} = 2.2 \,{\rm kcal\, mol}^{-1}$ in the vapor phase, 0.91 kcal mol−1 in CCl4 and −1.18 kcal mol−1 in DMSO. The 3JNF coupling was independent of the molecular conformation, as it did not change with the solvent polarity. Copyright © 2003 John Wiley & Sons, Ltd.

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Studies on the conformational equilibria of 2-methoxy, 2-methylthio, and 2-methylselenocyclohexanol are reported. Dynamic NMR spectroscopy experiments at 203-210 K were performed, which provided the percentages of each conformer in equilibrium. Theoretical calculations using the B3LYP method and aug-cc-pvdz basis set were applied to determine the differences in energy between the conformers. The analysis of the potential energy surface of each conformer showed the presence of two rotamers. Natural bond orbital analysis provided an explanation of which factors are driving the rotamer and conformer preferences.