Ex-vivo confocal Raman microspectroscopy of porcine skin with 633/785-NM laser excitation and optical clearing with glycerol/water/DMSO solution

Ali Jaafar,Anton Y Sdobnov,László Himics,Roman Holomb,Malik H Mahmood,Miklós Veres,Valery V Tuchin,Tamás Váczi

doi:10.1142/s1793545821420037

Abstract

Confocal Raman microspectroscopy (CRM) with 633- and 785-nm excitation wavelengths combined with optical clearing (OC) technique was used for ex-vivo study of porcine skin in the Raman fingerprint region. The optical clearing has been performed on the skin samples by applying a mixture of glycerol and distilled water and a mixture of glycerol, distilled water and chemical penetration enhancer dimethyl sulfoxide (DMSO) during 30[Formula: see text]min and 60[Formula: see text]min of treatment. It was shown that the combined use of the optical clearing technique and CRM at 633[Formula: see text]nm allowed one to preserve the high probing depth, signal-to-noise ratio and spectral resolution simultaneously. Comparing the effect of different optical clearing agents on porcine skin showed that an optical clearing agent containing chemical penetration enhancer provides higher optical clearing efficiency. Also, an increase in treatment time allows to improve the optical clearing efficiency of both optical clearing agents. As a result of optical clearing, the detection of the amide-III spectral region indicating well-distinguishable structural differences between the type-I and type-IV collagens has been improved.

Highlights

We present an investigation of optical clearing agents (OCAs)' in°uence on probing depth using porcine skin with confocal Raman microspectroscopy (CRM) assessment
The principal Raman peaks of skin are located at 937 cmÀ1 (C–C stretch backbone), 1003 cmÀ1, 1246 cmÀ1, 1271 cmÀ1, 1426 cmÀ1 (C–C stretching vibrations) and 1665 cmÀ1 at a depth of 0 m
It was shown that the principal Raman peak intensities of skin are signicantly increased at all observed depths after OCAs treatment for 30 min and 60 min for both the excitations

Summary

Introduction

There has been increasing research interest in biomedical photonics, with the main focus on the development of in-vivo techniques and methods allowing for noninvasive skin disease diagnosis and monitoring of penetration and permeation of drugs and cosmetics into the skin as well as for the investigation of their action.[1,2] There are numerous noninvasive optical techniques, including but not limited to the confocal Raman microspectroscopy (CRM),[3,4,5,6] Raman spectroscopy (RS) and coherent anti-Stokes Raman spectroscopy (CARS),[4,7] optical coherence tomography (OCT),[8,9,10] multiphoton tomography (MPT),[11,12,13,14] including laser scanning microscopy (LSM),15 °uorescence spectroscopy[16,17] and terahertz spectroscopy,[18,19] and other methods,[20,21] which have been successfully implemented in vitro and in vivo for tissue physiological evaluation and diagnosis of skin pathophysiology.[22]. The e®ect of Raman scattering has been discovered in 1928.23 In general, this e®ect can be described using the quantum theory In this way, the interaction of photons of emitted light with tissue molecules leads to photon scattering. The Raman peaks give information about the bonding conguration of functional groups, and the molecule can be identied from a combination of Raman bands or based on previous data on a given sample system In this way, the analysis of Raman spectra allows obtaining information about the biochemical properties of the observed tissue.[24] even slightest changes in tissue composition lead to changes in Raman peaks' position and intensity; CRM can be used as an e®ective tool for early diagnosis of skin diseases and monitoring age-related changes. In the case of the skin, the recorded Raman spectrum representsngerprint signatures for the chemical composition of various tissue components such as collagen, blood, proteins, lipids and nucleic acids.[25]

Methods

Results

Conclusion