CC BY
11B-I-14
Integrated effects on skin immersion optical clearing in vivo
E. Genina1,2, A. Bashkatov1,2, V. Tuchin1,2,3, V. Zharov4
1Saratov State University, Optics and Biophotonics, Saratov, Russian Federation 2Tomsk State University, Interdisciplinary Laboratory of Biophotonics, Tomsk, Russian Federation
3Institute of Precision Mechanics and Control RAS, Laboratory of laser diagnostics of technical and living systems, Saratov, Russian Federation
4University of Arkansas for Medical Sciences, Arkansas Nanomedicine Center, Little Rock, USA
The use of optical clearing agents makes it possible to increase the probing depth of non-invasive optical diagnostic methods. However, the protective epidermal barrier of the skin prevents the penetration of hydrophilic immersion liquids into the deeper layers of the skin. The aim of this study is to improve the efficiency of skin optical clearing by increasing the permeability of the epidermis for polyethylene glycol with MW 300 (PEG-300) using different approaches.
We present the results of a comparative analysis of optical immersion clearing of skin in laboratory rats in vivo with and without preliminary ablation of epidermis, fraction microablation and/or sonophoresis. Laser ablation and microablation has been implemented using a setup based on a pulsed erbium laser (X= 2940 nm) with different hand-pieces. Sonophoresis has been applied with the following parameters: 1 MHz, 1 W/cm2, continuous mode. As an optical clearing agent (OCA) PEG-300 has been used. Basing on optical coherence tomography, we have estimated the scattering coefficient in the process of optical clearing in 2 regions at depths of 50 - 170 mm and 150 - 400 mm.
The results have shown that both surface and fraction ablation of skin in vivo lead to the local edema of the affected region that increases the scattering coefficient. However, the intense evaporation of water from the ablation zone facilitates the optical clearing at the expense of tissue dehydration, particularly in the upper layers. Besides, ablation enhances the transepidermal penetration of OCA. Sonophoresis also provides effective penetration of OCA into dermis. Time dependences of the skin optical clearing efficiency for separate and combined laser irradiation and therapeutic ultrasound action have been obtained.
