Vyacheslav I. Kochubey

Glucose and Mannitol Diffusion in Human Dura Mater

An in vitro experimental study of the control of the human dura mater optical properties at administration of aqueous solutions of glucose and mannitol has been presented. The significant increase of the dura mater optical transmittance under action of immersion liquids has been demonstrated. Diffusion coefficients of glucose and mannitol in the human dura mater tissue at 20 degrees C have been estimated as (1.63 +/- 0.29) x 10(-6)cm(2)/s and as (1.31 +/- 0.41) x 10(-6) cm(2)/s, respectively. Experiments show that administration of immersion liquids allows for the effective control of tissue optical characteristics that make dura mater more transparent, thereby increasing the ability of light penetration through the tissue.

Optical Properties of the Subcutaneous Adipose Tissue in the Spectral Range 400-2500 nm

The optical characteristics of subcutaneous adipose tissue are studied in the wavelength range 400–2500 nm. The experiments are conducted in vitro using a Cary 2415 spectrophotometer. Based on the measured diffuse reflectance and total transmittance spectra, the spectra of the absorption and transport scattering coefficients are calculated in terms of the inverse adding-doubling method.

In vitro and in vivo study of dye diffusion into the human skin and hair follicles

We present experimental results on the in vitro and in vivo study of dye diffusion into human skin and hair follicles. We have studied some commercially available dyes for potential using in the laser selective thermolysis. The degree and the depth of hair follicle dyeing inside the skin were determined. For hairs in different stages the sebaceous gland was stated as a reservoir for a dye administration. It was found that the penetration depth of dyes is about 1.2 mm from the skin surface. We have developed the biocompatible Indocyanine Green lotions and the method for in vivo dyeing and dye in depth monitoring. Shift on 16-21 nm of absorption peak of Indocyanine Green to the longer wavelengths due to Indocyanine Green binding with cell proteins in the human skin was found.

Optical properties of human cranial bone in the spectral range from 800 to 2000 nm

The optical properties of human cranial bones were measured in the wavelength range 800-2000 nm. The measurements were carried out using the commercially available spectrophotometer with an integrating sphere. The inverse adding-doubling method was used to determine the absorption and reduced scattering coefficients from the measurements.

Optical Clearing of Human Dura Mater

The changes in the optical parameters of the human dura mater in the spectral range 400–700 nm caused by the action of an aqueous solution of mannitol with a concentration of 0.16 g/ml are studied in vitro. The diffusion of mannitol into the tissue leads to a partial matching between the refractive indices of the structure-forming elements (the collagen fibrils) and the base substance of the dura mater (the interstitial fluid). As a result, the light scattering by the biological tissue in the entire spectral range under study is decreased, on the average, by a factor of 1.5–2. The immersion of the biological tissue is shown to cause a decrease in the absorption of the dura mater in the range of the blood absorption bands by a factor of 1.2–1.6. The results presented may prove to be useful in the laser therapy and optical diagnostics of brain diseases.

Estimation of wavelength dependence of refractive index of collagen fibers of scleral tissue

We present experimental results and computer modeling on the optical properties of the human scleral tissue. The wavelength dependence of the refractive index of collagen fibers in the human scleral tissue was estimated on the base of Mie theory. Dispersion formula describing this dependence was derived. The results are general and can be used to describe optical properties of many other fibrous tissues.

Optical properties of melanin in the skin and skinlike phantoms

Experimental study and computer modeling were used to investigate the optical properties of melanin in the skin and skin-like phantoms. To investigate light scattering by melanosomes in skin we made skin-like phantoms on the base of gelatin with different content of melanin particles. Spectra of total transmittance and diffuse reflectance of the phantoms were obtained in the wavelength range from 400 to 800 nm. Absorption and reduced scattering coefficients of melanin were calculated. Mie theory was used to estimate the optical properties of melanin particles. Wavelength dependence of refractive indices of eumelanin particles (isolated and purified from the ink of the cuttlefish Sepia officinalis) and synthetic melanin particles was estimated.

In-vivo and in-vitro study of control of rat skin optical properties by action of osmotical liquid

We present experimental results on optical properties of the rat skin controlled by administration of osmotically active chemical, such as glycerol. In vivo reflectance and in vitro reflectance and transmittance spectra of the rat skin were measured. Results of experimental study of influence of glycerol on reflectance spectra of the rat skin are presented. The significant increase of transmittance and decrease of reflectance of the rat skin under action of osmotical agent are demonstrated. Basing on mathematical modeling the optical parameters of the rat skin are determined.

Human sclera dynamic spectra: in-vitro and in-vivo measurements

Experimental results on the optical properties of the human eye sclera controlled by administration of osmotically active chemicals, such as propylene glycol and glucose are presented. Administration of chemical agents induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Experimental study of influence of propylene glycol and glucose on reflectance and transmittance spectra of human eye sclera was performed. In vitro diffusion reflectance spectra of the whole human eye and transmittance spectra of the sclera samples were investigated. In vivo measurements were fulfilled on a rabbit eyes. The significant increase of transmittance and decrease of reflectance of human eye sclera and rabbit eye under action of osmolytic liquids was demonstrated. The matter diffusion coefficient for the scleral samples impregnated by glucose solution was estimated; the average value is 1.27x10-5 ± 2.26x10-6 cm2/sec. The results are general and can be used to describe many other fibrous tissues.

Transcutaneous delivery of micro- and nanoparticles with laser microporation

Abstract. Fractional laser ablation is one of the relatively safe and minimally invasive methods used to administer micro- and nanoparticles into the skin at sufficiently large depth. In this article, we present the results of delivery of TiO2 nanoparticles and Al2O3 microparticles into skin. Fractional laser microablation of skin was provided by a system based on a pulsed Er:YAG laser with the following parameters: the wavelength 2940 nm, the pulse energy 3.0 J, and the pulse duration 20 ms. Ex vivo and in vivo human skin was used in the study. The suspensions of titanium dioxide and alumina powder in polyethylene glycol with particle size of about 100 nm and 27 μm, respectively, were used. In the ex vivo experiments, reflectance spectra of skin samples with administered particles were measured and histological sections of the samples were made. In the in vivo experiment, reflectance spectroscopy, optical coherence tomography, and clinical photography were used to monitor the skin status during one month after suspension administering. It is shown that particles can be delivered into dermis up to the depth 230 μm and distributed uniformly in the tissue. Spectral measurements confirm that the particles stay in the dermis longer than 1 month.