Daria K. Tuchina

Skin optical clearing potential of disaccharides

Abstract. Skin optical clearing can significantly enhance the ability of biomedical optical imaging. Some alcohols and sugars have been selected to be optical clearing agents (OCAs). In this work, we paid attention to the optical clearing potential of disaccharides. Sucrose and maltose were chosen as typical disaccharides to compare with fructose, an excellent monosaccharide-OCA, by using molecular dynamics simulation and an ex vivo experiment. The experimental results indicated that the optical clearing efficacy of skin increases linearly with the concentration for each OCA. Both the theoretical predication and experimental results revealed that the two disaccharides exerted a better optical clearing potential than fructose at the same concentration, and sucrose is optimal. Since maltose has an extremely low saturation concentration, the other two OCAs with saturation concentrations were treated topically on rat skin in vivo, and optical coherence tomography imaging was applied to monitor the optical clearing process. The results demonstrated that sucrose could cause a more significant increase in imaging depth and signal intensity than fructose.

Ex vivo investigation of glycerol diffusion in skin tissue

The change of optical parameters of rat skin ex vivo under the action of aqueous 30%, 50%, 60%, 70%, 85%, and 100% glycerol solutions has been experimentally studied. The analysis of kinetics of the change of the studied parameters has allowed the estimate of the diffusion coefficient dependence upon the concentration of glycerol in the skin and the efficiency of optical clearing for each of the glycerol solutions. The results can find application in the development of new methods of noninvasive diagnostics and therapy of skin diseases.

Quantification of glucose and glycerol diffusion in myocardium

The results on determination of glucose and glycerol diffusion coefficients in myocardium tissue are presented. The method is based on the measurement and analysis of temporal dependence of tissue optical collimated transmittance under action of a hyperosmotic agent. This temporal tissue response is related to the rate of the agent and water diffusion in a tissue. The diffusion coefficients for tissue fluid fluxes at glucose and glycerol application to the myocardium at 20°C have been estimated as (4.75 ± 3.40) × 10-7 and (7.71 ± 4.63) × 10-7 cm2/s, respectively.

In-vitro terahertz spectroscopy of rat skin under the action of dehydrating agents

In the paper we present the results of study of rat skin and rat subcutaneous tumor under the action of dehydrating agents in terahertz (THz) range (15-30 THz). Frustrated Total Internal Reflection (FTIR) spectra were obtained with infrared Fourier spectrometer Nicolet 6700 and then they were recalculated in the transmittance spectra with Omnic software. Experiments were carried out with healthy and xenografted tumor in skin tissue in vitro. As the dehydrating agents 100% glycerol, 40%-water glucose solution, PEG-600, and propylene glycol were used. To determine the effect of the optical clearing agent (OCA), the alterations of terahertz transmittance for the samples were analyzed. The results have shown that PEG-600 and 40%-glucose water solution are the most effective dehydrating agent. The transmittance of healthy skin after PEG-600 application increased approximately by 6% and the transmittance of tumor tissue after PEG- 600 and 40%-glucose water solution application increased approximately by 8%. Obtained data can be useful for further application of terahertz radiation for tumor diagnostics.

Laser speckle contrast imaging of cerebral blood flow of newborn mice at optical clearing

In this work, we consider the use of optical clearing agents to improve imaging quality of the cerebral blood flow of newborn mice. Aqueous 60%-glycerol solution, aqueous 70%-OmnipaqueTM(300) solution and OmnipaqueTM (300) solution in water/DMSO(25%/5%) were selected as the optical clearing agents. Laser speckle contrast imaging (LSCI) was used for imaging of cerebral blood flow in newborn mice brain during topical optical clearing of tissuesin the area of the fontanelle. These results demonstrate the effectiveness of glycerol and Omnipaque solutions as optical clearing agents for investigation of cerebral blood flow in newborn mice without scalp removing and skull thinning.

Study of glycerol diffusion in skin and myocardium ex vivo under the conditions of developing alloxan-induced diabetes

Diabetes mellitus is one of widespread diseases, the development of which impairs the functioning of organism vital organs. The study of the processes that occur in tissues under diabetic conditions facilitates the development of diabetes diagnostics and treatment methods, as well as the prognosis of its complications. The paper reports a comparative study of glycerol diffusion in skin and myocardium of rats ex vivo in the normal condition and the conditions of alloxan-induced diabetes. The glycerol diffusion coefficients in tissues were determined basing on the analysis of kinetics of collimated light transmittance through tissue samples immersed in 70%-glycerol solution. As a result, it was shown that the glycerol diffusion rate in the tissues of rats with alloxan-induced diabetes is essentially decreased as compared to the control group.

Terahertz spectroscopy of immersion optical clearing agents: DMSO, PG, EG, PEG

Application of terahertz (THz) spectroscopy for biological tissues is strongly limited by the extremely low penetration depth due to THz absorption by tissue water. One of the possible solution of such problem is the usage of THz wave penetration-enhancing agents (PEA) for optical clearing of tissues. In the present paper, the transmission-mode THz spectroscopy of a set of PEAs (polyethylene glycol with different molecular weight, propylene glycol, ethylene glycol, and dimethyl sulfoxide) was performed in order to reconstruct their dielectric properties and compare them with that of water. The obtained results emphasize the feasibility of using PEG to enhance the depth of THz wave penetration into tissues.

Controlling of upconversion nanoparticle luminescence at heating and optical clearing of adipose tissue

The luminescence spectra of a polymer film with embedded upconversion nanoparticles (UCNPs) were measured through 0.1-0.3 mm adipose tissue layer at heating in a wide temperature range. Heating and application of optical clearing agents improved intensity of UCNP fluorescence significantly.