Analytical data of synthesized deuterated isopropyl myristate and data about the influence of IPM/IPMdeut on the thermodynamics and morphology of 2D Stratum Corneum models

The data in this article shows the effect of isopropyl myristate (IPM) on a 2D Stratum Corneum lipid model. In the first part, the analytical characterization of the synthesized deuterated isopropyl myristate is given. Then a BAM image of the pure Stratum Corneum model used is shown and a dataset of surface-pressure – area isotherms considering various ratios of deuterated and non-deuterated IPM and the Stratum Corneum model mixture is provided. Assuming that after the plateau in the isotherm the area per molecule corresponds only to the Stratum Corneum model (squeezing out of IPM), the value of the area will correspond to the percentage of these lipids in the mixture when considering the pure SC model. The comparison of the real and the calculated areas per molecule is also done.


a b s t r a c t
The data in this article shows the effect of isopropyl myristate (IPM) on a 2D Stratum Corneum lipid model. In the first part, the analytical characterization of the synthesized deuterated isopropyl myristate is given. Then a BAM image of the pure Stratum Corneum model used is shown and a dataset of surface-pressurearea isotherms considering various ratios of deuterated and nondeuterated IPM and the Stratum Corneum model mixture is provided. Assuming that after the plateau in the isotherm the area per molecule corresponds only to the Stratum Corneum model (squeezing out of IPM), the value of the area will correspond to the percentage of these lipids in the mixture when considering the pure SC model. The comparison of the real and the calculated areas per molecule is also done.
& Validation of 2D models by direct comparison of deuterated and non-deuterated molecules.

Analytical characterization of the newly synthesized and purified deuterated isopropyl myristate
The analytical characterization of the newly synthetized and purified deuterated isopropyl myristate was performed by HPLC, HRMS and NMR as shown in Figs. 1-4.

Data of Langmuir monolayers considering deuterated and non-deuterated isopropyl myristate, Stratum Corneum lipid models and their mixtures
The Stratum Corneum (SC) is the outermost layer of our skin and the main problem when addressing topical/transdermal delivery drugs [1]. Langmuir monolayers serve as simple biological models to study the interaction between molecules, as for instance the effect of a penetration enhancer in the SC [2]. As a SC lipid model a mixture of ceramide [AP], stearic acid and cholesterol in a   Ceramide [AP] presents diastereomers: the D-form, which occurs naturally in our skin, and the L-form, which exists only if synthetized. Therefore, a SC model with only the D-form of ceramide [AP] in a mixture with the other two components -which will be called D-SC -is a better model of the human skin lipids. Fig. 6 shows the surface pressurearea isotherms of isopropyl myristate, pure D-SC monolayer and the mixture of the two in different ratios. For comparison and validation reasons the systems with non-deuterated isopropyl myristate (on the left) are compared with the deuterated ones (on the right), and the area per molecule (obtained by averaging the molecular weight of the molecules present in the mixtures) in such isotherms at selected surface pressures is presented in Table 1. In Table 2 the comparison of such areas regarding the calculated area corresponding to the ratio of D-SC present in the mixture is shown.    The surface-pressure area isotherms were also measured for the SC model with the racemic mixture of ceramide [AP] (isotherms presented in [3]). Table 3 shows the area per molecule taken from the isotherm of the different systems, while Table 4 shows the comparison of such areas regarding the calculated area corresponding to the ratio of SC present in the mixture.

Experimental design, materials and methods
Analytical characterization of the newly synthetized and purified deuterated Isopropyl myristate  A BAM2plus from NanoFilm Technologie (Göttingen, Germany) equipped with a miniature film balance from NIMA Technology (Coventry, UK) was used to image the morphology of the monolayer. The microscope has a frequency-doubled Nd-YAG laser (532 nm, $ 50 mW), a polarizer, an analyzer, and a CCD camera. When p-polarized light is directed onto the pure air/water interface at the Brewster angle ( $53.1°), zero reflectivity is observed. When a monolayer is added, the light starts to be reflected because of the different refractive index of the surface layer. The reflected light is registered by the CCD camera after passing the analyzer. BAM images of 355 Â 470 mm 2 were digitally recorded during compression of the monolayer with a resolution of approx. 2 mm.

Isotherms
The pressure-area isotherms were recorded on a computer interfaced home-made Langmuir trough. The trough is equipped with a Wilhelmy balance using a glass plate. The compression speed was 3 Å 2 molecule -1 min -1 . The temperature was kept constant at (2170.1)°C. Isotherms were measured three times on individually prepared samples to check for reproducibility. The isotherms were plotted in Origin 9 and the area per molecule was read directly from the graph at the surface-pressure considered. The calculated area corresponding to the ratio of SC model present in the mixture was obtained by multiplying the area obtained in the isotherm by the percentage of SC in the mixture. For example, at 35 mN/m the area per molecule of the SC model is 30 Å 2 . Considering the mixture with 90 mol% SC, the calculated area which corresponds to the SC is 27 Å 2 .