Layers Of Biological Tissues Research Articles

Mathematical model for constructing a matrix of coefficients thermal conductivity under low-temperature influence on the multilayer epidermis of biological tissue

Objective. The purpose of the study is to develop a mathematical model for constructing a matrix of thermal conductivity coefficients under low-temperature exposure to the multilayer epidermis of biological tissue. Method. The research is based on methods of thermo dynamic analysis, full-scale and computational modeling of processes under low-temperature influence. Result. A mathematical model of the matrix of thermal conductivity coefficients under low-temperature effects on biological tissue has been developed. Heat transfer in a multilayer medium under low-temperature influence on biological tissue is presented as a process with a discrete step in time and coordinate. Thermal properties are evenly distributed throughout the volume of layers of biological tissue. For exposure to cold, layers of the epidermis of biological tissue were used, divided into uniform identical cells, where the cell area of the biological tissue was taken to be equal to one. Conclusion. The results obtained in this work can be useful to specialists who deal with modeling problems with free boundaries.

3D polarization-interference holographic histology for wavelet-based differentiation of the polycrystalline component of biological tissues with different necrotic states. Forensic applications.

The interference-holographic method of phase scanning of fields of scattered laser radiation is proposed. The effectiveness of this method for the selection of variously dispersed components is demonstrated. This method made it possible to obtain polarization maps of biological tissues at a high level of depolarized background. The scale-selective analysis of such maps was used to determine necrotic changes in the optically anisotropic architectonics of biological tissues. Development and experimental approbation of layered phase polarimetry of repeatedly scattered fields in diffuse layers of biological tissues. Application of scale-selective processing of the found coordinate distributions of polarization states in various phase sections of object fields. Determination of criteria (markers) for histological differential diagnosis of the causes of necrotic changes in optical anisotropy of biological tissues. We used a synthesis of three instrumental and analytical methods. Polarization-interference registration of laser radiation scattered by a sample of biological tissue. Digital holographic reconstruction and layered phase scanning of distributions of complex amplitudes of the object field. Analytical determination of polarization maps of various phase cross-sections of repeatedly scattered radiation. Application of wavelet analysis of the distributions of polarization states in the phase plane of a single scattered component of an object field. Determination of criteria (markers) for differential diagnosis of necrotic changes in biological tissues with different morphological structure. Two cases are considered. The first case is the myocardium of those who died as a result of coronary heart disease and acute coronary insufficiency. The second case is lung tissue samples of deceased with bronchial asthma and fibrosis. A method of polarization-interference mapping of diffuse object fields of biological tissues has been developed and experimentally implemented. With the help of digital holographic reconstruction of the distributions of complex amplitudes, polarization maps in various phase sections of a diffuse object field are found. The wavelet analysis of azimuth and ellipticity distributions of polarization in the phase plane of a single scattered component of laser radiation is used. Scenarios for changing the amplitude of the wavelet coefficients for different scales of the scanning salt-like MHAT function are determined. Statistical moments of the first to fourth orders are determined for the distributions of the amplitudes of the wavelet coefficients of the azimuth maps and the ellipticity of polarization. As a result, diagnostic markers of necrotic changes in the myocardium and lung tissue were determined. The statistical criteria found are the basis for determining the accuracy of their differential diagnosis of various necrotic states of biological tissues. Necrotic changes caused by "coronary artery disease-acute coronary insufficiency" and "asthma-pulmonary fibrosis" were demonstrated by the method of wavelet differentiation with polarization interference with excellent accuracy.

О распространении микроволнового излучения в слоистых биотканях грудной клетки человека

The features of microwave propagation have been studied in a model of layered biotissue simulating a section of the human chest in a GHz frequency range. The model contained four layers (skin, subcutaneous fat, muscle, lung), and is bounded by a rectangular parallelepiped. The selection of layer thicknesses was carried out basing on the biological model of the human body. The following frequencies were selected for numerical simulation: 1, 2, 5, 10, 20, 50 and 100 GHz. The transverse size of the model and the incident wave front were chosen to be equal to 5λ, excluding an influence of wave diffraction on the lateral surface of the model on wave propagation along the axis of the model. The choice of the thickness of the last layer in the model ensured minimization of interference effects with the wave penetrating into the model from its back surface. As a result of modeling, the features of microwave propagation in layered biological tissue were revealed and the dependence of the depth of penetration of microwave radiation into the biostructure on the frequency was calculated.

Investigation of the dependence of temperature attenuation of the layered bio-tissue

High-intensity focused ultrasound for solid tumor ablation is a noninvasive ultrasound hyperthermia technique wherein ultrasound is transmitted through multiple layers of biological tissues, focusing on the target area. The resulting heat accumulates in the target tissue, leading to irreversible cell death or protein necrosis, achieving tumor ablation. During treatment, the efficiency of acoustic energy converting to heat is closely related to temperature attenuation in the layered tissues. To obtain an accurate prediction of thermal damage, variations in the acoustic parameters should be measured at different temperatures. This study used two methods to induce heating to the tissues: the water heating method (WHM), which involves heat transfer from the outside to the inside, and the ultrasound heating method (UHM), wherein the heat source is located inside the tissue. The finite-amplitude insertion-substitution method was utilized to determine the attenuation coefficients of various bio-tissues such as porcine fat, muscle, and liver as the temperature increased. To mitigate the effects of viscous heating artifacts, the ‘wait then measure’ (WTM) thermometric approach was utilized using wire thermocouples to measure the temperature of the ultrasound-heated tissue. Experimental results demonstrate that the attenuation coefficient of bio-tissues varies with temperature under different heating methods. This study presents the variation in tissue attenuation using WHM at 5 MHz, while tissue categories using UHM are modeled with formulas at a frequency of 2 MHz.

Комп’ютерний сингулярний аналіз процесів лазерної автофлуоресценції двопроменезаломлюючих біологічних тканин

The analytical conditions for the formation of singularities of the Jones matrix elements of birefringent networks of biological tissues are determined. The correlation between coordinate positions of characteristic points of two-dimensional elements of the Mueller matrix of an optically thin layer of biological tissue and the network of S- and C-points in its laser image is established. The effectiveness of the Mueller matrix singular diagnostics of not only oncological changes in the myometrial tissue, but also the differentiation of their severity is demonstrated.

Biaxial tensile testing system for measuring mechanical properties of both sides of biological tissues

The aortic wall exhibits a unique elastic behavior, periodically expanding in aortic diameter by approximately 10% during heartbeats. This elastic behavior of the aortic wall relies on the distinct yet interacting mechanical properties of its three layers: intima, media, and adventitia. Aortic aneurysms develop as a result of multifactorial remodeling influenced by mechanical vulnerability of the aortic wall. Therefore, investigating the mechanical response of the aneurysmal wall, in conjunction with changes in microstructural parameters on both the intimal and adventitial sides, may offer valuable insights into the mechanisms of aortic aneurysm development or rupture. This study aimed to develop a biaxial tensile testing system to measure the mechanical properties of both sides of the tissue to gain insights concerning the interactions in anisotropic layered tissue. The biaxial tensile test set-up consisted of four motors, four cameras, four load cells, and a toggle switch. Porcine ascending aortas were chosen as the test subject. Graphite particles with diameters of approximately 5–11 [μm] were randomly applied to both sides of the aorta. Strain measurements were obtained using the stereo digital-image correlation method. Because stretching a rectangular specimen with a thread inevitably concentrates and localizes stress, to reduce this effect the specimen's shape was investigated using finite element analysis.The finite element analysis showed that a cross-shaped specimen with diagonally cut edges would be suitable. Therefore, we prepared specimens with this novel shape. This test system showed that mechanical response of the aortic tissue was significantly different between the intimal and adventitial side in the high-strain range, due to the disruption of collagen fibers. The adventitia side exhibited a smaller elastic modulus than the intimal side, accompanied by disruption of collagen fibers in the adventitia, which were more pronounced in the longitudinal direction. In contrast, in the mid-strain range, the elastic modulus did not differ between the intimal and adventitial sides, irrespective of longitudinal or circumferential direction, and collagen fibers were not disrupted but elongated.A biaxial tensile test system, which measures the mechanical properties of both sides of biological tissues and the shape of the specimen for reducing the concentration of stress at the chuck region, was developed in this study. The biaxial tensile testing system developed here is useful for better understanding the influences of mechanical loads and tissue degeneration on anisotropic, layered biological tissues.

Comparison of the Penetration Depth of 905 nm and 1064 nm Laser Light in Surface Layers of Biological Tissue Ex Vivo.

The choice of parameters for laser beams used in the treatment of musculoskeletal diseases is of great importance. First, to reach high penetration depths into biological tissue and, secondly, to achieve the required effects on a molecular level. The penetration depth depends on the wavelength since there are multiple light-absorbing and scattering molecules in tissue with different absorption spectra. The present study is the first comparing the penetration depth of 1064 nm laser light with light of a smaller wavelength (905 nm) using high-fidelity laser measurement technology. Penetration depths in two types of tissue ex vivo (porcine skin and bovine muscle) were investigated. The transmittance of 1064 nm light through both tissue types was consistently higher than of 905 nm light. The largest differences (up to 5.9%) were seen in the upper 10 mm of tissue, while the difference vanished with increasing tissue thickness. Overall, the differences in penetration depth were comparably small. These results may be of relevance in the selection of a certain wavelength in the treatment of musculoskeletal diseases with laser therapy.

Tissue-Mimicking Materials for Ultrasound-Guided Needle Intervention Phantoms: A Comprehensive Review.

Ultrasound-guided needle interventions are common procedures in medicine, and tissue-mimicking phantoms are widely used for simulation training to bridge the gap between theory and clinical practice in a controlled environment. This review assesses tissue-mimicking materials from 24 studies as candidates for a high-fidelity ultrasound phantom, including methods for evaluating relevant acoustic and mechanical properties and to what extent the reported materials mimic the superficial layers of biological tissue. Speed of sound, acoustic attenuation, Young's modulus, hardness, needle interaction forces, training efficiency and material limitations were systematically evaluated. Although gelatin and agar have the closest acoustic values to tissue, mechanical properties are limited, and strict storage protocols must be employed to counteract dehydration and microbial growth. Polyvinyl chloride (PVC) has superior mechanical properties and is a suitable alternative if durability is desired and some ultrasound realism to human tissue may be sacrificed. Polyvinyl alcohol (PVA), while also requiring hydration, performs well across all categories. Furthermore, we propose a framework for the evaluation of future ultrasound-guided needle intervention tissue phantoms to increase the fidelity of training programs and thereby improve clinical performance.

APPLICATION OF DIFFUSIVE TOMOGRAPHY METHOD OF BIOLOGICAL PREPARATIONS IN FOREIGN MEDICAL DIFFERENTIAL DIAGNOSIS OF ALCOHOLIC AND ALCOHOLOGEN POISONING

The article presents the results of the study of forensic effi cacy of diff erential diagnosis of alcohol and carbon monoxide poisoning, as well as establishing the age of death in these cases by diff use tomography of fl uctuations of linear fl uctuations of linear birefringence of human biological tissues.
 Aim of the work. Investigation of the eff ectiveness of the method of diff use tomography of biological products and polycrystalline blood fi lms in the forensic diff erential diagnosis of alcohol and carbon monoxide poisoning and determining the age of death in these cases.Materials and methods. The object of the study were histological samples of human internal organs (brain, myocardium) and polycrystalline blood fi lms in cases of death from ethanol poisoning, carbon monoxide and coronary heart disease (control group) with diff erent ages (6 to 48 hours). The study was performed using the method of diff use tomography of fl uctuations in the parameters of optical anisotropy of layers of biological tissues and fl uids.Results. The eff ectiveness of analytical determination of the age of death in cases of ethanol and carbon monoxide poisoning by analyzing the range of linear changes in the magnitude of statistical moments of 1-4 orders of magnitude, ranging from 24 to 60 hours. The accuracy of determining the age of death is 0.5 hours.Conclusion. The eff ectiveness of the method of diff use tomography of fl uctuations of linear birefringence of layers of biological tissues and fl uids in diff erentiating the cause of death in cases of ethanol and CO poisoning, as well as diagnosing the age of death in these cases.

Disordered metamaterial coating for daytime passive radiative cooling

In this theoretical study, a disordered metamaterial coating with randomly embedded TiO2 dielectric microspheres in a polydimethylsiloxane matrix has been designed for the purpose of daytime passive radiative cooling. While retaining the necessary optical properties of high reflectivity (≈94%) in the solar spectrum and high emissivity (≈96%) in the atmospheric transparency window, the coating exhibits the following additional desirable properties: (a) low volume fraction of TiO2 microspheres, ensuring minimal possibility of agglomeration of particles during fabrication; and (b) a cooling power of 81.8 W/m2, which is among the highest for similar coatings that have been developed. We also show how a modified form of Kubelka–Munk theory with empirical relations originally developed to analyze optical scattering in biological tissue layers can be used for designing radiative cooling structures. The predictions from this method have been validated using Monte Carlo simulations. It is expected that this study will motivate further similar designs in the rapidly expanding market for effective and easy-to-fabricate coatings for daytime passive radiative cooling applications.

Hybrid CNN Based Computer-Aided Diagnosis System for Choroidal Neovascularization, Diabetic Macular Edema, Drusen Disease Detection from OCT Images

In the treatment of eye diseases, optical coherence tomography (OCT) is a medical imaging method that displays biological tissue layers by taking high resolution tomographic sections at the micron level. It has an important role in the diagnosis and follow-up of many diseases such as Choroidal Neovascularization (CNV), Diabetic Macular Edema (DME), age-related macular degeneration (AMD), Diabetic Retinopathy, Central Serous Retinopathy, Epiretinal Membrane, and Macular Hole. Computer-Aided Diagnostic (CAD) tools are needed in early detection and treatment monitoring of such eye diseases. In this paper, a hybrid Convolutional Neural Networks-based CAD system, which can classify Diabetic Macular Edema (DME), Drusen Choroidal Neovascularization (CNV), and normal OCT images, is proposed. The proposed system is CNN-SVM (Convolutional Neural Networks – Support Vector Machine) model and doesn’t require any additional extraction of feature or noise filtering on OCT images. A total of 968 OCT images is classified in pre-trained CNN methods with Alexnet, Resnet18 and Googlenet. Accuracy is achieved with highest Googlenet 97.4%. To examine the performance of the proposed CAD system, the CNN-SVM method achieves 98.96% with the highest accuracy hybrid Alexnet-SVM model, which is implemented with Alexnet-SVM, Resnet18-SVM and Googlenet-SVM models.

A Weighted Average Phase Velocity Inversion Model for Depth-Resolved Elasticity Evaluation in Human Skin In-Vivo.

In current surface acoustic wave (SAW) elastography field, wavelength-depth inversion model is a straightforward and widely used inversion model for depth-resolved elasticity profile reconstruction. However, the elasticity directly evaluated from the wavelength-depth relationship is biased. Thus, a new inversion model, termed weighted average phase velocity (WAPV) inversion model, is proposed to provide depth-resolved Young's modulus estimate with better accuracy. The forward model for SAW phase velocity dispersion curve generation was derived from the numerical simulations of SAWs in layered materials, and inversion was implemented by matching the measured phase velocity dispersion curve to the one generated from the forward model using the least squares fitting. Three two-layer agar phantoms with different top-layer thicknesses and one three-layer agar phantom were tested to validate the proposed inversion model. Then the model was demonstrated on human skin at various sites (palm, forearm and back of hand) in-vivo. In multi-layered agar phantoms, depth-resolved elasticity estimates provided by the model have a maximal total inversion error of 15.2% per sample after inversion error compensation. In in-vivo human skin, the quantified bulk Young's moduli (palm: 212 ± 78 kPa; forearm: 32 ± 11 kPa and back of hand: 29 ± 8 kPa) are comparable to the reference values in the literature. The WAPV inversion model can provide accurate depth-resolved Young's modulus estimates in layered biological soft tissues. The proposed model can predict depth-resolved elasticity in layered biological soft tissues with a reasonable accuracy which traditional wavelength-depth inversion model cannot provide.

Optical Coherence Tomography findings in patients with Multiple Substance Use Disorder

Objective Optical Coherence Tomography (OCT) is a relatively new diagnosis method displaying biological tissue layers by with high-resolution sections. In the present study, the purpose was to examine the OCT findings of patients with Multiple Substance Use Disorder (MSUD) by comparing these findings with healthy controls. Methods The study included 30 MSUD and 30 controls. Detailed biomicroscopic examinations were carried out for all participants, and intraocular pressure, followed by OCT. The central macular thickness (CMT), mean macular thickness (MMT), mean macular volume (MMV), and retinal nerve fibre layer thickness (RNFL) were measured by using OCT. Results It was determined that the MMT and CMT were thinned in both eyes compared to the healthy controls. The MMV was decreased in both eyes in patients with substance use disorders compared to healthy controls. The RNFL and total thickness were thickened in temporal and inferior parts in patients with MSUD in both eyes compared to healthy. In the superior quadrant, thickening was detected only in the left eye. Conclusions Based on our results obtained here, it was concluded that vision-related findings should be carefully questioned and evaluated when treatment is planned for patients with substance use.

Numerical simulation of electromagnetic heating process of biological tissue via time-fractional Cattaneo transfer equation.

In order to simulate the heat transfer in the process of hyperthermia, one-dimensional time-fractional Cattaneo heat transfer equation (TFHE) is established. Based on TFHE, the heat transfer model is solved by using finite difference method, because a single layer of biological tissue in vitro is irradiated by electromagnetic energy. The effect of power parameters (energy flux density P0, tissue attenuation coefficient h) and equation parameters (relaxation time τq and fractional order β) on the prediction of temperature simulated by TFHE were studied. Furthermore, comparative studies on TFHE, Pennes and CV are performed and evaluated. In the heating process, because of the existence of relaxation time τq, the temperature response of TFHE and CV are later than Pennes, leading to the lower temperature prediction of TFHE and CV than that of Pennes. The shorter the time is, the higher the energy is, and the more obvious the difference is.

Scattering Compensation for Deep Brain Microscopy: The Long Road to Get Proper Images

Multiphoton microscopy is the most widespread method for preclinical brain imaging when sub-micrometer resolution is required. Nonetheless, even in the case of optimal experimental conditions, only a few hundred micrometers under the brain surface can be imaged by multiphoton microscopy. The main limitation preventing the acquisition of images from deep brain structures is the random light scattering which, until recently, was considered an unsurmountable obstacle. When in 2007 a breakthrough work by Vellekoop and Mosk [1] proved it is indeed possible to compensate for random scattering by using high resolution phase modulators, the neuro-photonics community started chasing the dream of a multiphoton microscopy capable of reaching arbitrary depths within the brain. Unfortunately, more than 10 years later, despite a massive improvement of technologies for scattering compensation in terms of speed, performances and reliability, clear images from deep layers of biological tissues are still lacking. In this work, we review recent technological and methodological advances in the field of multiphoton microscopy analyzing the big issue of scattering compensation. We will highlight the limits hampering image acquisition, and we will try to analyze the road scientists must tackle to target one of the most challenging issue in the field of biomedical imaging.

DYNAMICS OF CHANGES IN TEMPERATURE PARAMETERS IN BIOLOGICAL TISSUES UNDER LASER RADIATION OF DIFFERENT WAVE LENGTHS

Background. The use of lasers is one of the promising directions in the development of therapy and surgery. The effect of low-intensity laser radiation (LR) in therapeutic doses activates regenerative processes in tissues, which allows stimulating regeneration processes due to the intensification of microcirculation of metabolic processes and also has an effect on neuro-reflex and humoral pain mechanisms and on pain receptors. There is a need to clearly establish the LR parameters that are important in the development and receipt of effective results of therapy. Diagnostics in vivo allows getting the opposite answer about the reaction of the body to radiation with different dose indicators, power density and wavelength without damaging the biological tissue.Objective. Since laser devices are used for many physiotherapeutic and diagnostic procedures, for the correct application of low-intensity LR, it is necessary to take into account all the structural features of the influence zone, as an example, human skin and the processes of interaction of this LR with layers of biological tissues. Under the influence of LR begins the course of a wide range of photophysical and photochemical changes, occurs the temperature rise on the surface of the irradiated skin and physicochemical transformations. The main purpose of the work was to determine the dynamics of changes in the temperature of the skin under the influence of LR.Methods. It was justified the use of mathematical dependence to determine the required dose of LR and a mathematical model for calculating the change in skin temperature under the influence of LR. An experiment was performed comparing the results of the calculation by mathematical model and the results of the experiment on the LR influence with wavelengths of 0.66 μm, 0.63 μm, and 0.46 μm on the nature and dynamics of temperature processes in the upper layers of the skin.Results. As a general result, data on the dynamics of changes in the temperature of the skin under the influence of LR are obtained. The results of the experiments and their comparison with the calculations of the mathematical model showed that there is a dependence of the temperature change on the structure and parameters of biological tissue, the power density of the LR, the radiation dose and the exposure time.Conclusions.According to the results of the work, it was concluded that a higher intensity of heat removal occurs in the skin of living tissues. This is mainly due to the microcirculation of organic liquids and blood.

Differential Mueller matrix imaging of partially depolarizing optically anisotropic biological tissues

Since recently, a number of innovative polarization-based optical imaging modalities have been introduced and extensively used in various biomedical applications, with an ultimate aim to attain the practical tool for the optical biopsy and functional characterization of biological tissues. The techniques utilize polarization properties of light and Mueller matrix mapping of microscopic images of histological sections of biological tissues or polycrystalline films of biological fluids. The main drawback of currently developed laser polarimetry approaches and Mueller matrix mapping techniques is poor reproducibility of experimental data. This is due to azimuthal dependence of polarization and ellipticity values of most matrix elements to sample orientation in respect to incidence light polarization. Current study aims to generalize the methods of laser polarimetry for diagnosis of partially depolarizing optically anisotropic biological tissues. A method of differential Mueller matrix mapping for reconstruction of linear and circular birefringence and dichroism parameter distributions of partially depolarizing layers of biological tissues of different morphological structure is introduced and practically implemented. The coordinate distributions of the value of the first-order differential matrix elements of histological sections of brain tissue with spatially structured, optically anisotropic fibrillar network, as well as of parenchymatous tissue of the rectum wall with an “islet” polycrystalline structure are determined. Within the statistical analysis of polarization reproduced distributions of the averaged parameters of phase and amplitude anisotropy, the significant sensitivity of the statistical moments of the third and fourth orders to changes in the polycrystalline structure of partially depolarizing layers of biological tissue is observed. The differentiation of female reproductive sphere connective tissue is realized with excellent accuracy. The differential Mueller matrix mapping method for reconstruction of distributions of linear and circular birefringence and dichroism parameters of partially depolarizing layers of biological tissues of different morphological structures is proposed and substantiated. Differential diagnostics of changes in the phase (good balanced accuracy) and amplitude (excellent balanced accuracy) of the anisotropy of the partially depolarizing layers of the vagina wall tissue with prolapse of the genitals is realized. The maximum diagnostic efficiency of the first-order differential matrix method was demonstrated in comparison with the traditional methods of polarization and Mueller matrix mapping of histological sections of light-scattering biological tissues.

Evaluation of oxygenation in the surface layers of biological tissues based on diffuse optical spectroscopy with automated calibration of measurements

To assess the oxygen saturation (oxygenation) in the surface layers of biological tissues (at a depth of 4 mm), a compact system based on diffuse optical spectroscopy (DOS) with reflective measurement geometry in the wavelength range of 520 – 590 nm is proposed. The experimental DOS device is based on a broadband LED source of probe radiation and a spectrometer using a fibre-optic radiation delivery system. To calculate the oxygenation, an original method is proposed based on measuring the intensity of scattered light at four different locations of the source and receiver on the surface of the object under study (four-measurement method). The developed method allows for the device hardware parameters (optical contact with the tissue, transient characteristics of the radiation delivery system) and does not require any additional calibration measurements. The results of testing the DOS system using the four-measurement method for monitoring the oxygen saturation of tissues during the artificial occlusion of the blood vessels agree with the published data of other research teams.

Impact of secondary particles on microdistribution of deposited dose in biological tissue in the presence of gold and gadolinium nanoparticles under photon beam irradiation

It is experimentally proven that nanoparticles of high-Z materials can be used as radiosensitizers for photon beam therapy. In the authors’ opinion, data available as of today on the impact of secondary particles (electrons, photons and positrons generated in biological tissue by penetrating beam of primary photons) on the distribution of deposited dose during photon beam therapy in the presence of nanoparticles, are insufficient. Investigation of this impact constituted the main goal of this work. Two-stage simulation was performed using Geant4 platform. During the first stage a layer of biological tissue (water) was irradiated by monoenergetic photon sources with energies ranging from 10 keV to 6 MeV. As the result of this modeling spectra of electrons, photons and positrons were obtained at the depth of 5 cm. During the second stage the obtained photon spectra were used to irradiate gold, gadolinium and water nanoparticles. Radial distributions of energy deposited around nanoparticles were obtained as the result of this modeling. Radial DEF (Dose Enhancement Factor) values around nanoparticles of gold and gadolinium positioned in water at the depth of 5 cm were obtained after processing the collected data. Contributions from primary photons and secondary particles (electrons, photons and positrons generated in the layer of water with 5-cm thickness by the penetrating beam of primary photons) in the additional dose deposited around the nanoparticles were calculated as well. It was demonstrated that layer of biological tissue placed between the source of photons and nanoparticles considerably changes the initial spectrum of photons and this change is significant in the analysis of mechanism of radiosensitization of biological tissues by nanoparticles for all energies of photon sources (up to 6 MeV). It was established that interaction of electrons and positrons with nanoparticles does not lead to significant increase of additional dose in the vicinity of their surfaces and can be most likely excluded from consideration in the analysis of radiosensitization mechanism of nanoparticles.

Indocyanine green based fluorescent polymeric nanoprobes for in vitro imaging.

Indocyanine green (ICG) provides an advantage in the imaging of deep tumors as it can reach deeper location without being absorbed in the upper layers of biological tissues in the wavelengths, which named "therapeutic window" in the tissue engineering. Unfortunately, rapid elimination and short-term stability in aqueous media limited its use as a fluorescence probe for the early detection of cancerous tissue. In this study, stabilization of ICG was performed by encapsulating ICG molecules into the biodegradable polymer composited with poly(l-lactic acid) and poly(ε-caprolactone) via a simple one-step multiaxial electrospinning method. Different types of coaxial and triaxial structure groups were performed and compared with single polymer only groups. Confocal microscopy was used to image the encapsulated ICG (1 mg/mL) within electrospun nanofibers and in vitro ICG uptake by MIA PaCa-2 pancreatic cancer cells. Stability of encapsulated ICG is demonstrated by the in vitro sustainable release profile in PBS (pH = 4 and 7) up to 21 days. These results suggest the potential of the ability of internalization and accommodation of ICG into the pancreatic cell cytoplasm from in vitro implanted ICG-encapsulated multiaxial nanofiber mats. ICG-encapsulated multilayer nanofibers may be promising for the local sustained delivery system to eliminate loss of dosage caused by direct injection of ICG-loaded nanoparticles in systemic administration.