The measurement of skin electrical resistance (SER) has drawn a great deal of attention for the rapid screening of transdermal penetration enhancers (PEs). However, the mechanisms underlying the SER measurement are still unclear. This study was to investigate the effects and mechanisms of seven oxygen-containing terpenes on the SER kinetics. Stratum corneum (SC) lipids were proved to play a key role in SER measurement. Then, the factors affecting the SER measurement were optimized. By the determination of SER kinetics, cyclic terpenes (1,8-cineole, terpinen-4-ol, menthol and α-terpineol) were demonstrated to possess higher enhancement ratio (ER) values compared with linear terpenes (linalool, geraniol and citral). For the first time, the linear correlation was found between ER of terpenes and the interaction energy of terpene–ceramide complexes revealed by molecular simulation. The attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis revealed that the effect of cyclic terpenes on SC lipid arrangement was obviously stronger than that of linear terpenes. In addition, by evaluating HaCaT skin cell viability, little difference was found between the toxicities of cyclic and linear terpenes. In conclusion, measurement of SER could be a feasible approach for the efficient evaluation of the PEs that mainly act on SC lipids.
Discotic liquid crystal consisting of polycyclic aromatic hydrocarbon (PAH) core and peripheral alkyl chains is a kind of soft organic materials showing semiconductivity and fluorescence, and it can be fabricated into opto-electronic devices by solution process or printing technique, with low-cost advantage. We report benzo[g]chrysene unsymmetrical functional discotic liquid crystals, which were synthesized by Suzuki-Miyaura cross-coupling reaction and Scholl oxidative annulation. Five new π-extended compounds containing ester, anhydride, imide and benzoimidazole unit were synthesized and characterized. Their liquid crystalline property was fully characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS), these compounds showed ordered columnar hexagonal (Colhex) mesophase with broad mesophase range as wide as 206 ℃. The functional groups have essential impact on the phase transition temperatures. The ultraviolet-visible (UV-Vis) absorption and photoluminescent property were studied, they displayed fluorescent quantum yield as high as 34% in solution, and the emission spectra can be tuned from blue, green to red by functional group and π-conjugation extension. Density functional theory (DFT) computation results explained these physical properties. We anticipate that more π-extended functional molecules can be developed from naphthalic anhydride by our method.
A prerequisite for successful transdermal or dermal drug therapy is the drug ability to penetration through the skin, especially stratum corneum (SC). The most acceptable technique for measuring skin permeation in vitro is the application of both the Franz diffusion cell device and the skin model. In the skin model, a liposome-based artificial skin membrane (LASM) consisting of tight layers of liposomes immobilized on a filter was prepared and characterized. Using porcine ear skin, rat skin and Strat-M™ artificial membrane as control, the LASM was then evaluated in permeation studies with five active compounds: ferulic acid, paeoniflorin, albiflorin, tetrahydrocolumbamine, and tetrahydropalmatine. The scanning electron microscope images demonstrated complete filling of the membrane pores with lipids and the formation of a continuous liposomal coating. The contents of egg phosphatidylcholine (EPC) and cholesterol in LASM were measured to be 12.08 ± 0.18 and 4.41 ± 0.04 mg/cm, respectively. Moreover, revealed by the measurement of electrical resistance, the LASM remains intact for at least 12 h with the incubation of 20% ethanol. The results of permeation studies demonstrated a good correlation (r= 0.9743, r = 0.9871) of P values between the drugs' permeation through LASM and porcine ear skin. In addition, by ATR-FTIR analysis, a slighter shift of CH stretching frequency between LASM and porcine ear skin was observed compared with the shift between Strat-M™ membrane and porcine ear skin. In summary, for the first time, the LASM has been proved to be a valuable alternative to porcine ear skin in permeation studies using Franz diffusion cell device.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.