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

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.

Confocal Raman Micro-Spectroscopy for Discrimination of Glycerol Diffusivity in Ex Vivo Porcine Dura Mater

“…To evaluate the glycerol concentration in DM during the OC process, the effect of the OC on the tissue optical properties and the efficiency of the Raman excitation has to be excluded. For this, first we determined the OC efficiency from the increase of the intensity of collagen-related Raman band (see Figure 2 D) as OC eff = I OC / I 0 , which is the ratio of the Raman band intensity after OCA treatment ( I OC ) to the Raman band intensity without treatment ( I 0 ), calculated at specific depth and time [ 56 , 78 , 79 ]. Then, we calculated the ratio of glycerol band intensities at 485 cm −1 measured during the experiment to OC eff of different collagen-related Raman bands to obtain the change solely of the reconstruction of the glycerol concentration.…”

In vivo skin optical clearing for improving imaging and light-induced therapy: a review

“…2(d) . Skin optical clearing also improved Raman spectroscopy to detect stronger and deeper Raman peaks of skin 68 and assisted surface-enhanced Raman scattering imaging in identifying the shape and boundary of the tumor phantom more accurately, 69 , 70 which would help determine the location of tumors and the presence of metastases. In addition, skin optical clearing increased detection sensitivity of circulating cells by flow cytometry 71 , 72 and improved the signal intensity and imaging depth of laser confocal microscopy when detecting monocytes in mice footpads, 31 as shown in Fig.…”

Monitoring Dermal Penetration and Permeation Kinetics of Topical Products; the Role of Raman Microspectroscopy

“…4), opening up new prospects for non-invasive, in situ/ in vivo monitoring of dermatological processes [8]. The use of optical clearing fluids has more recently been explored to reduce scattering and improve light penetration [73,74], and the state of the art of CRM for probing the physiological structure of the SC has recently been reviewed by Darvin et al [75].…”