Efficacy of radiopaque substances in optical clearing and their impact on red blood cell aggregation

Abstract

To increase the depth of penetration of visible and near-infrared radiation into the biological tissues to enhance the efficacy of diagnostic and therapeutic procedures, numerous techniques are used to increase the image contrast, in particular, optical clearing [1]. Typically, optical clearing agents (OCAs) are used for this purpose. The mechanism of the OCA action is based on the reduction of the reflectance from the tissue surface and diffuse penetration of the OCA into the deep layers of tissues. The second process results in the reduction of the amount of multiple light scattering by equalizing the relative refractive index of the light scattering nonhomogeneities inside the investigated tissue. These makes the tissues optically more homogeneous, which results in the increase of the depth and resolution of imaging techniques, for example the digital capillaroscopy method for in vivo visualization of terminal capillaries in the nail bed area [2].
One of the aims of this work was to study the efficacy of various OCA which are already used in clinical practice as radiopaque substances for improving the visualization of subsurface structures. The measurements were taken within the nail bed using optical coherence tomography (OCT). Another goal of this work was to investigate the effect of these OCA on the aggregation of rat’s red blood cells (RBCs) to study the mechanisms of OCAs affecting the blood flow after their administration into the blood stream. In this study seven different OCAs, including magnevist, gadovist, visipaque, mixture of visipaque and DMSO (90% and 10%, correspondingly), mixture of visipaque and polypropylene glycol 400 (40% and 60%, correspondingly), accupaque and a solution consisting of visipaque 54%, DMSO 10%, polypropylene glycol 36% were applied to the nail beds of 6 healthy volunteers. Each sample was imaged using a high-resolution OCT GAN930V2-BU (Thorlabs, USA), (wavelength 930±5 nm) before and during 15 minutes of treatment with the OCA. The results were evaluated based on the changes in the attenuation coefficient calculated from the OCT scan images. It was shown that almost all OCAs are effective in the optical clearing of nail beds. For example, after application of gadovist attenuation coefficient decreased by 16 ± 8% at a depth of 0 - 50 μm. In order to study the effect of OCA on aggregation of RBCs two OCAs were chosen: magnevist and gadovist. Samples of blood with different concentrations (1%, 5% and 10%) of these OCAs were measured with a laser aggregometer RheoScan (RheoMeditech, Republic of Korea). According to the obtained experimental data, aggregation of RBCs decreases with the increase in the concentration of OCA. For samples with 10% concentration of the magnevist and gadovist the decrease is 56 ± 14% and 45 ± 12% respectively. This study allows us to expand the scope of application of these agents in optical clearing of tissues, visualizing the capillaries [3] and to shed some light on their interaction with RBCs in the blood stream.
This work was supported by the Russian Science Foundation (Grant No. 23-45-00027)
[1] E. Genina, A. Bashkatov, Y. Sinichkin, I. Yanina, V. Tuchin. Optical clearing of biological tissues: Prospects of application in medical diagnostics and phototherapy [Review]. Journal of Biomedical Science and Engineering. 1. 22-58 (2015).
[2] P. Moldon, P. Ermolinskiy, A. Lugovtsov, P. Timoshina, E. Lazareva, Yu. Surkov, Yu. Gurfinkel, V. Tuchin, A. Priezzhev. Influence of optical clearing agents on the scattering properties of human nail bed and blood microrheological properties: in vivo and in vitro study. J. Biophoton. 2024, 17, e202300524
[3] A. Lugovtsov, Y. Gurfinkel, P. Ermolinskiy, A. Maslyanitsina, L. Dyachuk, A. Priezzhev. Optical assessment of alterations of microrheologic and microcirculation parameters in cardiovascular diseases. Biomedical Optics Express. 10. 3974-3986 (2019).

Speaker

Moldon Pavel Aleksandrovich
Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia
Russia

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