Accepted Article Controlling the near infrared transparency of costal cartilage by impregnation with clearing agents and magnetite nanoparticles Yulia Alexandrovskaya 1,2,3* , Kirill Sadovnikov 3 , Andrey Sharov 3 , Anna Sherstneva 3 , Evgeniy Evtushenko 3 , Alexander Omelchenko 1,2 , Mariya Obrezkova 3 , Valery Tuchin 4,5,6 , Valery Lunin 3 and Emil Sobol 1,2 1 Institute of Applied Physics of the Russian Academy of Sciences, Ul'yanov St. 46, 603950 Nizhny Novgorod, Russia 2 Institute of Photon Technologies, Federal Scientific Research Centre "Crystallography and Photonics" of the Russian Academy of Sciences, Pionerskaya St. 2, 142190 Troitsk, Moscow, Russia 3 M.V. Lomonosov Moscow State University, Leninskiye Gory 3, 119991 Moscow, Russia 4 Research-Educational Institute of Optics and Biophotonics, National Research Saratov State University, Astrakhanskaya St. 83, 410012 Saratov, Russia 5 Laboratory of Laser Diagnostics of Technical and Living Systems, Institute of Precision Mechanics and Control RAS, Rabochaya St. 24, 410028 Saratov, Russia 6 Interdisciplinary Laboratory of Biophotonics, National Research Tomsk State University, Lenin’s avenue 36, 634050 Tomsk, Russia Received zzz, revised zzz, accepted zzz Published online zzz Key words: near infrared laser, optical clearing, costal cartilage, magnetite nanoparticles 1. Introduction Near infrared (NIR) lasers are nowadays widely used in clinical diagnostics and therapy [1-3], in particular for correction of cartilage shape in otolaryngology. [4] Absorption of NIR radiation (from 700 to 2500 nm) by the tissue macromolecules is quite small and usually water is the principal NIR chromophore. Water absorption in NIR region varies in about four orders of magnitude [5] and it determines the penetration depth of NIR laser radiation to the tissue for the chosen Penetration depth of near infrared laser radiation to costal cartilage is controlled by the tissue absorption and scattering and it is the critical parameter to provide the relaxation of mechanical stress throughout the whole thickness of cartilage implant. To enhance the penetration for the laser radiation on 1.56 µm the optical clearing solutions of glycerol and fructose of various concentrations are tested. The effective and reversible tissue clearance was achieved. However, the increasing absorption of radiation should be concerned: 5- 8 ᴼ C increase of tissue temperature was detected. Laser parameters used for stress relaxation in cartilage should be optimized when applying optical clearing agents (OCAs). To concentrate the absorption in the superficial tissue layers magnetite nanoparticle (NP) dispersions with the mean size 95±5 nm and concentration 3.9±1.1x10 11 particles/ml are applied. The significant increase in the tissue heating rate was observed along with the decrease in its transparency. Using NPs the respective laser power can be decreased allowing us to obtain the working temperature locally with reduced thermal effect on the surrounding tissue. Diagrams of transmitted laser radiation intensity on λ=1.56 μm through cartilage impregnated with different agents and kinetics of temperature on the tissue surface in the course of its laser irradiation * Corresponding author: e-mail yu.alexandrovskaya@gmail.com This article is protected by copyright. All rights reserved. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jbio.201700105