Follow-up of drug permeation through excised human skin with confocal Raman microspectroscopy

Abstract

Skin is a multilayered organ which covers and protects the surface of human body by providing a barrier function against exogenous agents. Meanwhile, the efficacy of several topically applicated drugs is directly related to their penetration through the skin barrier. Several techniques are commonly used to evaluate the rate, the speed and the depth of penetration of these drugs, but few of them can provide real-time results. Therefore, the use of nondestructive and structurally informative techniques permits a real breakthrough in the investigations on skin penetration at a microscopic scale. Confocal Raman microspectroscopy is a nondestructive and rapid technique which allows information to be obtained from deep layers under the skin surface, giving the possibility of a real-time tracking of the drug in the skin layers. The specific Raman signature of the drug enables its identification in the skin. In this study, we try to follow the penetration of Metronidazole, a drug produced by Galderma as a therapeutic agent for Rosacea treatment, through the skin. The first step was the spectral characterization of Metronidazole in the skin. Then micro-axial profiles were conducted to follow the penetration of the drug in the superficial layers, on excised human skin specimens. For more accurate information, transverse sections were cut from the skin and spectral images were conducted, giving information down to several millimeters deep. Moreover, the collected spectra permit us to follow the structural modifications, induced by the Metronidazole on the skin, by studying the changes in the spectral signature of the skin constituents.

Towards drug quantification in human skin with confocal Raman microscopy

“…So far, most studies relied on a relative method to deal with Raman signal attenuation. By applying this method, the intensity of a drug representing Raman peak is related to a skin derived Raman peak [12,18].…”

“…Furthermore, the influence of skin inhomogenities on concentration depth profiles is reduced. On the contrary to the existing qualitative and semiquantitative studies, this facilitates the acquisition of quantitative concentration depth profiles [9,12]. However, future studies will investigate the applicability of the developed algorithm on a larger set of different drug depth profiles including a comparison of Raman spectroscopy results and established standard techniques for the acquisition of drug depth profiles.…”

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

“…One approach to overcome the influence of Raman signal attenuation in skin was already performed by relating the intensity of a drug Raman peak to the intensity of a skin derived Raman peak [12,18]. Unfortunately, potential inhomogenities due to the complex skin structure cannot be taken into consideration with this relative method.…”

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

“…[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.…”