Stratum corneum (SC) is comprised of lipids, protein and low molecular weight water-soluble components. Changes in these skin micro constituents can be understood by instrumental methods like differential scanning calorimetry (DSC) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The former provides information about changes in thermotropic behavior of SC lipids and proteins, whereas the latter provides data about alterations at molecular and conformational level. Most of the DSC thermograms of intact mammalian SC show two reversible and two irreversible transitions in the temperature range of 25-125 degrees C. The reversible endotherms are ascribed to lipid melting transitions, whereas the irreversible endotherms are ascribed to protein denaturation. Similarly, the FTIR spectral bands of SC occurring between 2920-2850 cm-1 and between 1650-1550 cm-1 have been suggested to arise from lipid and protein molecular vibrations, respectively. Treatment of skin with solvents or permeation enhancers alters the composition of lipids or their molecular arrangement in the skin microenvironment, which leads to changes in permeability of drug molecules. Furthermore, inhibition of lipid synthesis in epidermis with concomitant decrease in enthalpy of lipid endothermic transitions and reduction in height and area of asymmetric and symmetric C-H stretching peaks have been found to be directly correlated with enhanced permeation of drugs. In addition, method of skin preparation, type of skin, types of enhancer etc. also influence both the nature and intensity of responses recorded in spectrographs and thermograms. Therefore, the modification in spectrographs and thermograms of skin samples treated with various enhancers, vehicles etc. are expected to provide better insight into their mechanism of action on the skin. This review article shall critically evaluate the thermotropic and infrared spectroscopic data of SC/epidermis after various treatments.
Nano-magnetic ferrites with composition Mg1−xZnxFe2O4 (x = 0.3, 0.4, 0.5, 0.6, and 0.7) have been prepared by coprecipitation method. X-ray diffraction (XRD) studies showed that the lattice parameter was found to increase from 8.402 to 8.424 Å with Zn2+ ion content from 0.3 to 0.7. Fourier transform infrared (FTIR) spectra revealed two prominent peaks corresponding to tetrahedral and octahedral at around 560 and 430 cm−1 respectively that confirmed the spinel phase of the samples. Transmission electron microscopy (TEM) images showed that the particle size was noted to increase from 18 to 24 nm with an increase in Zn content from x = 0.3 to 0.7. The magnetic properties were studied by vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) which ascertained the superparamagnetic behavior of the samples and contribution of superexchange interactions. The maximum magnetization was found to vary from 23.80 to 32.78 emu/g that increased till x = 0.5 and decreased thereafter. Further, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and substantiate their oxidation states.
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