Gaussian-function-based deconvolution method to determine the penetration ability of petrolatum oil into in vivo human skin using confocal Raman microscopy

Abstract

Human skin pre-treated with petrolatum was analyzed in vivo using confocal Raman microscopy in order to determine the penetration depth of the oil into the skin. The broad Raman peak (2820–3030 cm−1) measured in vivo on human skin in the high wavenumber region exhibits two prominent main Raman peaks at 2880 cm−1 and 2935 cm−1 that originated from cutaneous lipids and keratin and two main peak shoulders at 2850 cm−1 and 2980 cm−1 that originated from lipids and keratin, respectively. Topical application of petrolatum oil onto the skin gives rise to an increase of the intensity of the broad lipid–keratin Raman peak (2820–3030 cm−1). Herewith, not only the intensity of the lipid part but also of the keratin part is increased, making the normalization to keratin and the determination of the petrolatum penetration profile erroneous. To solve this problem, the Gaussian-function-based deconvolution method is introduced in analyzing the Raman spectrum of the lipid–keratin peak and the least square method is applied for analyzing the petrolatum penetration profile. Results obtained in vivo show that the petrolatum oil does not penetrate deeper than 10 µm into intact human skin.