Tissue optical clearing: State of the art and prospects

The term “tissue optical clearing” (TOC) came into use at the end of the 20th century and is associated with the development of methods for controlling tissue scattering properties using the refractive index matching effect. However, the first mention of increasing the transparency of biological tissues using immersion agents can be attributed to the work of Spalteholz in 1914, in which an organic solvent-based technique was applied to tissue samples in vitro. The next step was made by Barer et al., in 1955, who proposed the optical clearing of cell suspensions by means of protein solution with the same refractive index as the cell cytoplasm

Nonequilibrium processes from Generalised Langevin Equations: realistic nanoscale systems connected to two thermal baths

We extend the Generalised Langevin Equation (GLE) method [Phys. Rev. B 89, 134303 (2014)] to model a central classical region connected to two realistic thermal baths at two different temperatures. In such nonequilibrium conditions a heat flow is established, via the central system, in between the two baths. The GLE-2B (GLE two baths) scheme permits us to have a realistic description of both the dissipative central system and its surrounding baths. Following the original GLE approach, the extended Langevin dynamics scheme is modified to take into account two sets of auxiliary degrees of freedom corresponding to the mapping of the vibrational properties of each bath. These auxiliary variables are then used to solve the non-Markovian dissipative dynamics of the central region. The resulting algorithm is used to study a model of a short Al nanowire connected to two baths. The results of the simulations using the GLE-2B approach are compared to the results of other simulations that were carried out using standard thermostatting approaches (based on Markovian Langevin and Nose-Hoover thermostats). We concentrate on the steady state regime and study the establishment of a local temperature profile within the system. The conditions for obtaining a flat profile or a temperature gradient are examined in detail, in agreement with earlier studies. The results show that the GLE-2B approach is able to treat, within a single scheme, two widely different thermal transport regimes, i.e. ballistic systems, with no temperature gradient, and diffusive systems with a temperature gradient.Comment: present version accepted for publication in Phys. Rev. B (Apr 2016

Glycerol effects on optical, weight and geometrical properties of skin tissue

Complex study of glycerol e®ects on the skin tissue was performed. The change in optical, weight and geometrical parameters of the rat skin under the action of the glycerol solutions was studied ex vivo. Possible mechanisms of the skin optical clearing under the action of glycerol solutions of di®erent concentrations were discussed. The results can be helpful for re¯nement of models developed to evaluate the e®ective di®usion coe±cients of glycerol in tissues

Estimation of beta-carotene using calibrated reflection spectroscopy method: phantom study

In this work, we use compression and immersio

Kinetics of rat skin optical clearing at topical application of 40%glucose: ex vivo and in vivo studies

Optical, molecule diffusion, and mechanical properties of skin and blood microcirculation in the underlying tissues at topical application of 40%-glucose solution in rats were investigated. Optical clearing of ex vivo and in vivo skin was measured within the wavelength range of 400-900 nm using standard spectrometer, and blood microcirculation alterations was measured with laser speckle contrast imaging. Increase of skin collimated transmittance, transverse, and along skin shrinkage and weight loss was observed for the first 20-60 min of immersion, for the longer time, tissue swelling was found. The glucose diffusion coefficients in ex vivo and in vivo rat skin were evaluated as (1.11 ± 0.78) × 10 -6 and (1.54 ± 0.28) × 10 -6 cm 2 /s, respectively. The decrease of average rate of microcirculation in 2.2 fold was observed. The results received allow one to evaluate glucose impact on skin tissue optical and mechanical properties and blood microcirculation

Visualisation of distribution of gold nanoparticles in liver tissues ex vivo and in vitro using the method of optical coherence tomography

Abstract. The possibility of visualising the distribution of gold nanoparticles in liver by means of the method of optical coherence tomography is studied experimentally in model samples of beef liver in vitro and rat liver ex vivo. In the experiments we used the gold nanoparticles in the form of nanocages with resonance absorption in the near-IR spectral region. In the model studies the suspension of nanoparticles was applied to the surface of the sample, which then was treated with ultrasound. In the ex vivo studies the suspension of nanoparticles was injected to the laboratory rats intravenously. The image contrast and the optical depth of detection of blood vessels and liver structure components are calculated, as well as the depth of liver optical probing before and after the injection of nanoparticles. It was shown that the administration of the nanoparticle increases significantly the imaging contrast of liver blood vessels owing to the localisation of the nanoparticles therein

Refractive properties of human adipose tissue at hyperthermic temperatures

The refractive index (RI) of human adipose tissu

A robust ex vivo method to evaluate the diffusion properties of agents in biological tissues

A robust method is presented for evaluating the diffusion properties of chemicals in ex vivo biological tissues. Using this method that relies only on thickness and collimated transmittance measurements, the diffusion properties of glycerol, fructose, polypropylene glycol and water in muscle tissues were evaluated. Amongst other results, the diffusion coefficient of glycerol in colorectal muscle was estimated with a value of 3.3 × 10−7 cm2/s. Due to the robustness and simplicity of the method, it can be used in other fields of biomedical engineering, namely in organ cryoprotection and food industry

Changes in optical properties of model cholangiocarcinoma after plasmon-resonant photothermal treatment

The heating degree of the inner layers of tumor tissue is an important parameter required to optimize plasmonic photothermal therapy (PPT). This study reports the optical properties of tissue layers of transplanted cholangiocarcinoma and covering tissues in rats without treatment (control group) and after PPT using gold nanorods (experimental group). PPT was carried out for 15 min, and the temperature on the skin surface reached 54.8 1.6 C. The following samples were cut out ex vivo and studied: skin, subcutaneous connective tissue, tumor capsule, top, center, and bottom part of the tumor. The samples’ absorption and reduced scattering coefficients were calculated using the inverse adding–doubling method at 350–2250 nm wavelength. Diffuse reflectance spectra of skin surface above tumors were measured in vivo in the control and experimental groups before and immediately after PPT in the wavelength range of 350–2150 nm. Our results indicate significant differences between the optical properties of the tissues before and after PPT. The differences are attributed to edema and hemorrhage in the surface layers, tissue dehydration of the deep tumor layers, and morphological changes during the heating