Geol, A; Tsikritsis, D; Belsey, N; Pendlington, R; Glavin, S; Chen, T (2023) Measurement of Chemical Penetration in Skin using Stimulated Raman Scattering Microscopy and Multivariate Curve Resolution - Alternating Least Squares. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 296. 122639

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Abstract

Skin penetration underpins the design, efficacy and risk assessment of many high-value products including functional personal care products, topical and transdermal drugs. Stimulated Raman scattering (SRS) microscopy, a label free chemical imaging tool, combines molecular spectroscopy with submicron spatial information to map the distribution of chemicals as they penetrate the skin. However, the quantification of penetration is hampered by significant interference from Raman signals of skin constituents. This study reports a method for disentangling of exogeneous contributions and measuring their permeation profile through human skin combining SRS measurements with chemometrics for spectral unmixing. We investigated the spectral decomposition capability of Multivariate Curve Resolution – Alternating Least Squares (MCR–ALS) using hyperspectral SRS images of skin dosed with 4-cyanophenol. By performing MCR-ALS on the fingerprint spectral data, the distribution of 4-cyanophenol in skin is estimated in an attempt to semi-quantify the amount permeated at different depths. The reconstructed distribution was compared with the experimental mapping of C≡N, a strong vibrational peak in 4-cyanophenol where the skin is spectroscopically silent. The similarity between MCR-ALS resolved and experimental distribution in skin dosed for 4 hours was 0.79 which improved to 0.91 for skin dosed for 1 hour. The correlation was observed to be lower for deeper layers of skin where SRS signal intensity is low which is an indication of low sensitivity of SRS. This work is the first demonstration, to the best of our knowledge, of combining SRS imaging technique with spectral unmixing methods for direct observation and mapping of the chemical penetration and distribution in biological tissues semi-quantitatively.

Item Type:	Article
Keywords:	Stimulated Raman Scattering Chemometrics Spectral Unmixing Topical delivery Multivariate analysis
Subjects:	Optical Radiation and Photonics > Bio-Medical
Divisions:	Chemical & Biological Sciences
Identification number/DOI:	10.1016/j.saa.2023.122639
Last Modified:	04 Jul 2023 14:32
URI:	https://eprintspublications.npl.co.uk/id/eprint/9775