Impact of optical clearing on ex vivo human skin optical properties characterized by spatially resolved multimodal spectroscopy

Abstract

A spatially resolved multimodal spectroscopic device was used on a two-layered "hybrid" model made of ex vivo skin and fluorescent gel to investigate the effect of skin optical clearing on the depth sensitivity of optical spectroscopy. Time kinetics of fluorescence and diffuse reflectance spectra were acquired in four experimental conditions: with optical clearing agent (OCA) 1 made of polyethylene glycol 400 (PEG-400), propylene glycol and sucrose; with OCA 2 made of PEG-400 and dimethyl sulfoxide (DMSO); with saline solution as control and a "dry" condition. An increase in the gel fluorescence back reflected intensitywas measured after optical clearing. Effect of OCA 2 turned out to be stronger than that of OCA 1, possibly due to DMSO impact on the stratum corneum keratin conformation. Complementary experimental results showed increased light transmittance through the skin and confirmed that the improvement in the depth sensitivity of the multimodal spectroscopic approach is related not only to the dehydration and refractive indices matching due to optical clearing, but also to the mechanical compression of tissues caused by the application of the spectroscopic probe.

Principles, developments, and applications of spatially resolved spectroscopy in agriculture: a review

“…In the field of biomedicine, SRS is widely used in human hemoglobin detection, skin pathology detection, and so on. It can help doctors to more accurately identify hemoglobin levels and the human condition so that they can precisely analyze the cause of the patient illness ( Zaytsev et al., 2022 ; Zhang et al., 2023 ). It can also be used to identify blood species to enhance wildlife protection and preserve national resource information ( Zhang et al., 2021 ).…”

Probing Dynamic Variation of Layered Microstructure Using Backscattering Polarization Imaging

“…Tissue optical clearing (TOC) is a convenient technique to increase the penetration depth of thick tissues [17][18][19][20][21][22]. The replacement of free water with optical clearing agents of higher refractive index, such as glycerin, causes refractive index matching between the scatterers and their surrounding media to reduce the scattering coefficient of biological tissues, which is often considered as one of the major mechanisms of TOC [23][24][25]. In fact, the optical properties of skins can be affected in many medical practices, such as the application of cosmetics or transdermal drug delivery [26,27].…”

Tissue Optical Clearing: State of the Art and Prospects

“…TOC in vivo and ex vivo is realized using biocompatible OCAs separately or in combination with chemical and physical actions for enhancement of tissue permeability. In this case, biologically safe solvents in small concentrations can be included into the content of OCAs [ 35 , 36 , 37 ]. The use of DMSO, sonophoresis, laser irradiation, microdermabrasion, microperforation and other enhancers of OCA penetration in tissues are described in Refs.…”