Feasibility of Tracking Phospholipid Permeation into Skin Using Infrared and Raman Microscopic Imaging

Abstract

The feasibility of monitoring the permeation of chain perdeuterated 1,2-dipalmitoylphosphatidylcholine (DPPC-d62) and 1-palmitoyl-d31, 2-oleoylphosphatidylcholine (P-d31OPC) vesicles into pigskin using infrared (IR) microscopic imaging and confocal Raman microscopy was demonstrated. The former technique permits the examination of the relative concentration of molecular species (e.g., endogenous and exogenous lipids and proteins) over spatial areas, approximately 1 mm, with a spatial resolution of approximately 10-12 microm. In contrast, Raman microscopy allows the confocal examination of tissue at depths up to 100 microm with a pixel size of about 2-3 microm3. Spectral signal/noise, however, is reduced from IR and significantly smaller areas are generally monitored. The permeation of the gel phase DPPC-d62 was limited to approximately 5-15 microm, whereas the liquid-crystalline phase P-d31OPC permeated to substantially greater depths (35-100 microm), at times ranging up to 24 h after application. The results are generally in accord with literature values. In addition, the state of the P-d31OPC (intact vesicles or molecularly dispersed with skin constituents) was evaluated from the spatial dependence of the deuteriopalmitate chain conformational order. Upon permeation, the chains became more ordered. The advantages and limitations of these imaging technologies are discussed.

Molecular characterization of reconstructed skin model by Raman microspectroscopy: Comparison with excised human skin

“…36,37 For their studies, Xiao et al used deuterated phospholipids. Labeling molecules with deuterium permits to facilitate their detection, since CÀ ÀD bonds arise between 2000 and 2250 cm 21 , a spectral domain free of vibrations from biological constituents.…”

“…[27][28][29][30][31][32][33][34] The follow-up, in real-time analysis, of the diffusion of the exogenous products through skin layers has also been performed. [35][36][37] To evaluate the potential of the Raman spectroscopy for future investigations on reconstructed skin samples, such as percutaneous absorption studies, toxicological risks investigations, drugs development, cosmetic products safety, and assessment of the effect of environmental aggressions like UV radiations, we have tried for the first time to establish a vibrational identity and a spectral characterization of a synthetic epidermis model, Episkin 1 , reconstructed from a culture of keratinocytes on a type-I collagen matrix. In a second time, we have realized a comparative study between the spectral signature of Episkin and the signature of human epidermis from excised skin.…”

Towards drug quantification in human skin with confocal Raman microscopy

“…In vitro follow-up studies of metronidazole [12] and phospholipids [13] indicated the potential of confocal Raman microscopy for penetration experiments.…”

Crossing biological barriers for advanced drug delivery

“…The majority of the experiments was performed in vitro with excised skin samples spanning from the characterization of barrier structures and changes upon cell maturation or diseased state up to permeation of substances and particles into skin [6].…”