Valery V. Tuchin

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.

Sapphire shaped crystals for laser-assisted cryodestruction of biological tissues

We have developed cryo-applicators based on the sapphire shaped crystals fabricated using the edge-defined film-fed growth (EFG) and noncapillary shaping (NCS) techniques. Due to the unique physical properties of sapphire: i.e. high thermal, mechanical, and chemical strength, impressive thermal conductivity and optical transparency, these cryo-applicators yield combination of the tissue cryo-destruction with its exposure to laser radiation for controlling the thermal regimes of cryosurgery, and with the optical diagnosis of tissue freezing. We have applied the proposed sapphire cryo-applicators for the destruction of tissues in vitro. The observed results highlight the prospectives of the sapphire cryo-applicators in cryosurgery.

Quantification of absolute blood velocity using LDA

Novel method of signal processing minimizing the effect of undesirable light scattering on estimation of Doppler frequency shift at blood flow velocity measurements has been proposed and tested using various phantoms with blood vessels and for humans in vivo.

Numerical modeling and analytical evaluation of light absorption by gold nanostars

In this paper, the regularity of local light absorption by gold nanostars (AuNSts) model is studied by method of numerical simulation. The mutual diffraction influence of individual geometric fragments of AuNSts is analyzed. A comparison is made with an approximate analytical approach for estimating the average bulk density of absorbed power and total absorbed power by individual geometric fragments of AuNSts. It is shown that the results of the approximate analytical estimate are in qualitative agreement with the numerical calculations of the light absorption by AuNSts.

Blood flow velocity measurements in chicken embryo vascular network via PIV approach

A method for measuring of blood velocity in the native vasculature of a chick embryo by the method of micro anemometry from particle images (μPIV) is improved. A method for interrogation regions sorting by the mask of the vasculature is proposed. A method for sorting of the velocity field of capillary blood flow is implemented. The in vitro method was evaluated for accuracy in a glass phantom of a blood vessel with a diameter of 50 μm and in vivo on the bloodstream of a chicken embryo, by comparing the transverse profile of the blood velocity obtained by the PIV method with the theoretical Poiseuille laminar flow profile.

Wavelet-domain de-noising of OCT images of human brain malignant glioma

We have proposed a wavelet-domain de-noising technique for imaging of human brain malignant glioma by optical coherence tomography (OCT). It implies OCT image decomposition using the direct fast wavelet transform, thresholding of the obtained wavelet spectrum and further inverse fast wavelet transform for image reconstruction. By selecting both wavelet basis and thresholding procedure, we have found an optimal wavelet filter, which application improves differentiation of the considered brain tissue classes – i.e. malignant glioma and normal/intact tissue. Namely, it allows reducing the scattering noise in the OCT images and retaining signal decrement for each tissue class. Therefore, the observed results reveals the wavelet-domain de-noising as a prospective tool for improved characterization of biological tissue using the OCT.

Corneal permeability for cement dust: prognosis for occupational safety

The high dust content in air of a working zone causes prevalence of pathologies of the anterior segment of the eye of workers of cement production. Therefore, studying of features of cement dust impact on structure of a cornea and development of ways of eye protection from this influence is relevant. In this work experimental studies were carried out with twenty eyes of ten rabbits. OCTtomography was used to monitor the light attenuation coefficient of the cornea in vitro during the permeability of cement dust and/or keratoprotector (Systein Ultra). The permeability coefficients of the cornea for water, cement dust and keratoprotector were measured. A computer model allowing one to analyze the diffusion of these substances in the eye cornea was developed. It was shown that 1) the cement dust falling on the eye cornea caused pronounced dehydration of the tissue (thickness decreasing) and led to the increase of the attenuation coefficient, which could affect the deterioration of the eyesight of workers in the conditions of cement production; 2) the application of the keratoprotector to the eye cornea when exposed by cement dust, slowed significantly the dehydration process and did not cause the increase of the attenuation coefficient that characterized the stabilization of visual functions. At this, the keratoprotector itself did not cause dehydration and led to the decrease of the attenuation coefficient, which could allow it to be used for a long time in the order to protect the organ of vision from the negative effects of cement dust.

Comparison of temperature sensing of the luminescent upconversion and ZnCdS nanoparticles

The luminescence spectra of upconversion nanoparticles (UCNPs) and ZnCdS nanoparticles (ZnCdSNPs) were measured and analyzed in a wide temperature range: from room to human body and further to a hyperthermic temperature resulting in tissue morphology change. The results show that the luminescence signal of UCNPs and ZnCdSNPs placed within the tissue is reasonably good sensitive to temperature change and accompanied by phase transitions of lipid structures of adipose tissue. The most likely that the multiple phase transitions are associated with the different components of fat cells, such as phospholipids of cell membrane and lipids of fat droplets. In the course of fat cell heating, lipids of fat droplet first transit from a crystalline form to a liquid crystal form and then to a liquid form, which is characterized by much less scattering. The results of phase transitions of lipids were observed as the changes in the slope of the temperature dependence of the intensity of luminescence of the film with nanoparticles embedded into tissue. The obtained results confirm a high sensitivity of the luminescent UCNPs and ZnCdSNPs to the temperature variations within thin tissue samples and show a strong potential for the controllable tissue thermolysis.

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.

Imaging and navigation of remote controlled nanostructured carriers for theranostics (Conference Presentation)

The modern medicine requires the new type of drug delivery carriers that will combine functions of in vivo navigation and visualization ability to deploy drug in controllable manner, including external triggering. This combination can be realized by multifunctional carriers produced by layer-by-layer assembly method. The carrier biodistribution can be controlled by a chosen mode of in vivo administration. Realization for chemical targeted delivery based on surface modification are not working well in vivo due to the corona effect [Kreyling W. et al., Nature Nanotech., 2015, 619]. Thus, physical targeting of drug delivery is more promising approach. It can be realized by gradient of magnetic field [Voronin D. et al., ACS App. Mater. & Interfaces, 2017, 6885], optical tweezers [Stetciura I. et al., Analyst, 2015,4981]. It was demonstrated that the sensitivity of nanostructured carriers to external influences as laser irradiation, ultrasound treatment can be changed by variation of volume fraction and chemical composition of inorganic nanoparticles in the carrier shell [Korolovych V. et al., PCCP, 2016,2389]. Same approach is applied for nanostructured carriers (NCs) imaging by MRI [German S. et al., PCCP, 2016, 32238], OCT [Genina E. et al., Biomed.Opt.Express, 2016, 2082] and photoacoustic method [Yashchenok A. et al., J. Biophotonics, 2016, 792] using magnetite and gold nanoparticles as contrast agents, respectively. Obtained NCs can be used as drug delivery systems including drug depot, combined much functionalities as navigation and visualization, in vivo monitoring of biochemical process, remote activated release of bioactive substances.