Synchronous fluorescence spectroscopy (SFS) is a steady-state approach that we used for evaluation of specific fluorescence characteristics of cancerous colorectal tissues. SFS allow narrowing of the fluorescence spectra received, which increase the spectral resolution and improve the analysis of the fluorescence origin in such complex objects, such as biological tissues. In our study we investigate the characteristic differences, with diagnostic meaning, in the synchronous fluorescence spectra (SFS) of cancerous and healthy colorectal tissues ex vivo using a spectrofluorimeter FluoroLog3 (HORIBA, JobinYvon, France) for obtaining of the SFS data in a broad spectral range (300-800 nm) using excitation in the range of 280-440 nm with a delta lambda between 0 and 200 nm with a 10 nm step between scanning excitation and emission data. The procedure of obtaining the investigated samples ex vivo includes their excision during surgery for removal of neoplasia lesions. After the surgical removal biological samples are transported in isothermal conditions and safekeeping solution from the hospital to the spectral laboratory, where their spectral properties were investigated. All patients received and signed written informed consent and this research is approved by Ethics committee of University Hospital “Tsaritsa Yoanna”, Sofia. Histological analysis was used as “gold standard” for evaluation of tissue samples and comparison of the spectral data received.

Langmuir monolayers of quantum dots could be used as a platform for creation of planar fluorescent sensors that widely used in biology during immunochemistry analysis. Interesting feature is a creation of matrix with separated quantum dots one from each other. The process of Langmuir monolayers of quantum dots and fatty acid mixtures with different component ratios formation was studied. The method of compression isotherm was used for Langmuir monolayer formation process characterization, atomic force microscopy was used for transferred films characterization. Volume component ratios of 1:1, 1:2. 2:1, 1:5 and 5:1 of arachidic acid and quantum dots were studied. Was shown that increasing of the arachidic acid concentration in the solution cause to decreasing the maximal monolayer area, changing in monolayers liquid phase extensions and type. Also the monolayer compressibility and compression module are changes and achieves a peak value at components ratio of 1:1. At the indicated component ratio the formed Langmuir monolayer of quantum dots and arachidic acid mixture was transferred on the glass substrate and studied by atomic force microscopy.

The studies were carried out on groups of clinically healthy mice line of outbred CD-1 stock. The model animals were divided into 2 groups and received experimental liposomal formulations. Using the method of fluorescence spectroscopy, we investigated the effectiveness of penetration into the circulatory system of fluorescently stained liposomes with polyethylene glycol (PEG) and without PEG when administered orally. Fluorescence channel with a fiber probe series of multifunctional laser non-invasive diagnostic system “LAKK-M” (SPE “LAZMA” Ltd, Russia) was used as the measuring equipment.

Aggregation of red blood cells (RBCs) is an intrinsic property of blood, which has direct effect on the blood viscosity and therefore affects overall the blood circulation throughout the body. It is attracting interest for the research in both fundamental science and clinical application. Despite of the intensive research, the aggregation mechanism is remaining not fully clear. Recent advances in methods allowed measuring the interaction between single RBCs in a well-defined configuration leading the better understanding of the mechanism of the process. However the most of the studies were made on the static cells. Thus, the measurements in flow mimicking conditions are missing. In this work, we aim to study the interaction of two RBCs in the flow conditions. We demonstrate the characterization of the cells interaction strength (or flow tolerance) by measuring the flow velocity to be applied to separate two aggregated cells trapped by double channel optical tweezers in a desired configuration. The age-separated cells were used for this study. The obtained values for the minimum flow velocities needed to separate the two cells were found to be 78.9 ± 6.1 μm/s and 110 ± 13 μm/s for old and young cells respectively. The data obtained is in agreement with the observations reported by other authors. The significance of our results is in ability for obtaining a comprehensible and absolute physical value characterizing the cells interaction in flow conditions (not like the Aggregation Index measured in whole blood suspensions by other techniques, which is some abstract parameter)

The protein contribution to the red blood cell (RBC) aggregation is studied using the in-house made two-channeled optical tweezers. The cells interaction was characterized using two forces: the force required for separating two cells (F_D – disaggregating force) and the force required for holding them from their spontaneous aggregation (F_A – aggregating force). The gamma globulin solutions with/without albumin were used to induce the RBC aggregation. The strong interaction (3-10 pN) between the cells was measured within the contact formed using optical tweezers. We found that F_D becomes stronger as the gamma globulin concentration increases, while the addition of albumin to the solution led to the significant (few fold) enhancement of the cells interaction forces. However, despite of the strong interaction between the cells their spontaneous overlapping was not observed, unlike the case in plasma, where the cells did increase their overlapping surface, when attached with small interacting surface and released from optical traps. This work in addition to our previous work with model solutions of fibrinogen allows us to conclude that the synergy of blood components is one of the most important features that contribute to the reversible RBC aggregation.

Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.

This article presents the results of the study of the pressure applied on optical diagnostic probes as a significant factor affecting the results of measurements. During stepwise increasing and decreasing of local pressure on skin we conducted measurements using the methods of laser Doppler flowmetry and fluorescence spectroscopy. It was found out that pressure on optical probe has sufficient impact on skin microcirculation to affect registered fluorescence intensity. Data obtained in this study are of interest for design and development of diagnostic technologies for wearable devices. This data will also inform further investigation into issues of compensation of blood absorption influence on fluorescence spectrum, allowing increased accuracy and reproducibility of measurements by fluorescence spectroscopy methods in optical diagnosis.

The resolution of the acousto-optical method for blood typing was estimated experimentally by means of two types of reagents: monoclonal antibodies and standard hemagglutinating sera. The peculiarity of this work is the application of digital photo images processing by pixel analysis previously proposed by the authors. The influence of the concentrations of reagents, of blood sample, which is to be tested, as well as of the duration of the ultrasonic action on the biological object upon the resolution of acousto-optical method were investigated. The optimal experimental conditions to obtain maximum of the resolution of the acousto-optical method were found, it creates the prerequisites for a reliable blood typing. The present paper is a further step in the development of acousto-optical method for determining human blood groups.

An algorithm for photographic images processing of blood samples in its native state was developed to determine the concentration of erythrocytes, leukocytes and platelets without individual separate preparation of cells’ samples. Special "photo templates" were suggested to use in order to identify red blood cells. The effect of "highlighting" of leukocytes, which was found by authors, was used to increase the accuracy of this type of cells counting. Finally to raise the resolution of platelets from leukocytes the areas of their photo images were used, but not their sizes. It is shown that the accuracy of cells counting for native blood samples may be comparable with the accuracy of similar studies for smears. At the same time the proposed native blood analysis simplifies greatly the procedure of sample preparation in comparison to smear, permits to move from the detection of blood cells ratio to the determination of their concentrations in the sample.

The results of in vitro pilot study of anterior lens capsule destruction by submicrosecond pulses of Yb,Er:Glass laser as well as results of 2% agar gel damage threshold investigation are presented. It was established that the local destruction of anterior lens capsule is possible without any ruptures at energy densities up to 25 J/cm² when exposed to 30 laser pulses, delivered via 200 μm optical quartz fiber. It was found that 2% agar gel damage threshold determined as minimal value of laser energy density required for appearance of the visually identifiable damage of agar gel decreases with the increase in the number of laser pulses. The 2% agar gel damage threshold on the air for a single laser pulse impact was about 2.3-3.3 J/cm², for 5 pulses impact – about 1.8-2.5 J/cm² and for 10 pulses impact – about 1.6-2.4 J/cm².

The results of in vitro study of the soft tissue temperature dynamics during 980 nm diode laser cutting by different types (CLEAR, FILM, VOLUMETRIC) of fiber opto-thermal converters (FOTC) are presented. It was found that the use of CLEAR fiber end (tip) at the laser power below 8.5 W doesn't lead to the soft tissue (chicken meat) destruction. The chicken meat destruction (cutting) begins when irradiated by 8.5 W laser radiation for approximately 9.0 s. At the power of 9.0 W this time decreases up to 7.0 s, at 9.5 W − to 6.0 s, at 10.0 W − to 3.5 s. The moment of soft tissue cutting start correlates with the moment of black layer (absorber) formation at the fiber end and appearance of visually identifiable laser cut walls on the photos; the temperature in this case rapidly increases up to 850 °C. It was determined that the FILM FOTC begins to cut the soft tissue immediately after exposure of laser radiation with power of 4.0 W, the temperature in this case reaches 900 °C. It was determined that the VOLUMETRIC FOTC begins to cut the tissue immediately after exposure at the power of 1.0 W, the temperature in this case reaches 600 °C. VOLUMETRIC FOTC can produce more effective cuts of the soft tissue at the laser power of 4.0 W, in this case, the temperature is above 1200 °C.

Specific method of transformation of nucleotide of gene into speckle pattern is suggested. Reference speckle pattern of omp1 gene of typical wild strains of Chlamydia trachomatis of genovars D, E, F, G, J and K and Chlamydia psittaci as well is generated. Perspectives of proposed technique in the gene identification and detection of natural genetic mutations as single nucleotide polymorphism (SNP) are demonstrated.

The current study was designed to investigate the dynamics of microbial biofilm-formation in standard and clinical strains of uropathogenic Escherichia coli (UPEC), using spectrophotometric and electron microscopic methods. For achieving this goal, three E. coli strains were used (one standard and two clinical). These isolates differ in the existence of fimH virulence gene. The process involved the using of electron microscopy and immunological microtitration plates under in vitro conditions for 96 hours. We found that standard and clinical strains of E. coli were capable of forming a microbial biofilm in vitro, with a higher intensity related to the clinical strain E. coli 245. The using of scanning electron microscopy confirmed the obtained results. The combined use of different optical methods gives a complete characterization of film-forming ability of pathogenic microorganisms.

The influence of red laser irradiation on the growth of colonies of methicillin-resistant strain of Staphylococcus aureus and photodynamic effects of the photosensitizers Photoditazine and Dimegin were performed. It was established that the red semiconductor laser (λ - 660 nm, 100 mW/cm²) at 10-, 15- and 30-mins exposure, has a direct bacteriostatic action on the growth of S. aureus. Pre-treatment of bacterial cells by Photoditazine significantly enhances the inhibitory effect. The photosensitizing action of Dimegin does not appear at influence on methicillin-resistant S. aureus.

Analysis of the influence of red laser irradiation on the processes of self-assembly of the core histones H2A and H2B was performed using a wedge dehydration method. Image-analysis of facies included their qualitative characteristics and calculation of quantitative parameters with subsequent statistical processing. It was established that linearly polarized red laser light (λ - 660 nm, 1 J/cm²) significantly modified the process of self-assembly of core histone H2B, whereas the structure of the facies of H2A histone changed to a lesser extent. Histones were used in the form of aqueous salt solutions. The effect of red light seems to result from the formation of singlet oxygen by direct laser excitation of molecular oxygen.

Investigation of fullerenol solutions with metal salts (magnesium sulfate and calcium chloride) by the laser correlation spectroscopy is presented. The results of the experimental study are discussed. Some peculiarities of interaction between fullerenol and different metal salts were observed. The results of the experiments revealed that fullerenol can be the chelate ligand that may be useful for medical applications.

Experimental FT-IR spectra of lemon peel are registered in the 650 - 3800 cm-1 range. The influence of peel artificial and natural dehydration on its vibrational spectrum is studied. The colored outer surface of lemon peel is proved not to have a significant impact on FT-IR spectrum. It is determined that only dehydration processes affect the FT-IR vibrational spectrum of the peel when a lemon is stored for 28 days under natural laboratory conditions. Polymer molecule models for dietary fibers, such as cellulose, hemicellulose, pectin, lignin, as well as hesperidin – flavonoid glycoside, and free moisture cluster are developed within the framework of DFT/B3LYP/6-31G(d) theoretical method. By implementing supramolecular approach, modeling of the vibrational FT-IR spectrum of lemon peel is carried out and its detailed theoretical interpretation is presented.

The interaction of three tissue-clearing agents (1,2-1,3-propanediol, 1,2-ethanediol) with the collagen mimetic peptide ((GPH)₃)₉ was studied by applying the method of classical molecular dynamics. The complete conformational analysis of the clearing agents under study was performed using the DFT/B3LYP/6-311+G method (d, p), the most energetically favorable spatial configurations were determined, the values of the Mulliken atomic charges were calculated which were used for the simulation. The research showed that there is a good correlation between the time of the hydrogen binding of a clearing agent with a collagen peptide and the potential of optical clearing. The paper also discusses that the interaction of the tissue-clearing agents with a collagen peptide in a water solution results in the 6% average enlargement of the distance between the alpha peptide chains. It has been suggested that such changes in a collagen structure can affect the refraction index and as a consequence the optical clearing of a biotissue. The dependences of the average distance changing between the alpha chains of a collagen peptide and the concentration of clearing agents in water solution were determined.

Intermolecular interaction of diamond-like nanoparticles and flavonoids is investigated by numerical simulation. Using molecular modelling by the density functional theory method, we analyze hydrogen bonds formation and their influence on IR - spectra and structure of molecular complex which is formed due to interaction between flavonoids and nanodiamonds surrounded with carboxylic groups. Enriched adamantane (1,3,5,7 - adamantanetetracarboxylic acid) is used as an example of diamond-like nanoparticles. Intermolecular forces and structure of hydrogen bonds are investigated. IR – spectra and structure parameters of quercetin - adamantanetetracarboxylic acid molecular complex are obtained by numerical simulation using the Gaussian software complex. Received data coincide well with experimental results. Intermolecular interactions and hydrogen bonding structure in the obtained molecular complex are examined. Possibilities of flavonoids interaction with DNA at the molecular level are also considered.

The application of gold nanoparticles (GNPs) for laser-induced cell transfection has been studied intensively during the past decade as efficient and gentle alternative to well-established molecule delivery methods like lipid-based transfection or electroporation. The method is based on temporal increase of membrane permeability induced by laser irradiation of GNPs attached to cell membranes. Although this approach is attractive due to high throughput and easy usability, it is not free from serious drawbacks related to random adsorption of GNPs during preincubation of cells with GNPs. This stage can affect the optoporation results because of potential nanoparticle toxicity, thus leading to decreased delivery efficiency and to low reproducibility of independent optoporation runs. Herein, we suggest a novel GNP-mediated laser transfection technique based on immobilized gold nanostars (GNSs) that are adsorbed on microplate wells and act as a plasmonic surface. The HeLa cells are grown directly on the monolayer of immobilized GNSs followed by CW NIR laser irradiation. We used the propidium iodide (PI) as a model transfecting agent to monitor simultaneously the delivery of PI into HeLa cells and their viability. These proof-of-the-concept experiments demonstrated enhanced penetration of PI into irradiated cells as compared to untreated ones.

The aim of this work was the fabrication of nanolabels (SERS-nanotags) which are used for chemical analysis by means of surface-enhanced Raman spectroscopy (SERS), and registration of their SERS spectra inside photonic crystal fibers (PCF). The SERS nanotags fabrication included synthesis of silver nanoparticles with subsequent deposition of Raman active layer (thiol-group contained aromatic compound) and protecting layer composed of silica shell. Finally, SERS spectra of the SERS nanotags were registered inside PCF in order to determine the value of fiber-enhancement of the Raman signal and to estimate analytical potential of this combination.

The use of photonic crystal fibers as a basis elements for biosensor construction is a perspective trend. The advantages of this approach are the use of micro and nano volumes of samples and a significant strengthening of the analytical signal while increasing the optical path length. Quantum dots are the most promising fluorescent markers for use in the photonic crystal fibers based analysis.

The advantages of quantum dots, in this case, are associated with stability, wide range of excitation and extremely narrow range of high luminescence intensity. In this work we have investigated the behavior and optical properties of CdSe core-shell nanocrystals (quantum dots) after they including into hollow central defect of hollow core chirped photonic crystal fibers with internal surface modified by polyaniline films.

In this article we report an effective and simple method for synthesis of high luminescent carbon nanodots (CDs). In our work as a carbon source sodium dextran sulfate (DS) was used because it is harmless, its analogs are used in medicine as antithrombotic compounds and blood substitutes after hemorrhage. was used as a substrate We investigated the influence of temperature parameters of hydrothermal synthesis on the photoluminescence (PL) intensity and position of emission maxima. We discovered that the PL intensity can be tuned by changing of synthesis temperature and CD concentration.

Polymeric nanoparticles (NPs) are widely used for drug delivery applications due to high biodegradability, low toxicity and high loading capacity. The focus of this study is the development of photosensitizer Photosens (PS) loaded albumin NPs for efficient photodynamic therapy (PDT). To fabricate PS-loaded bovine serum albumin nanoparticles (BSA-PS NPs), we used a coacervation method with glutaraldehyde followed by passive loading of PS. Successful loading of PS was confirmed by appearance of characteristic peak in absorption spectrum which allows to determine the PS loading in BSA NPs. The synthesized BSA-PS NPs demonstrated low toxicity to HeLa cells at therapeutic concentrations of loaded PS. Compared to free PS solution, the synthesized BSA-PS NPs generated the singlet oxygen more effectively under laser irradiation at 660 nm. In addition, due to presence of various chemical groups on the surface of BSA-PS NPs, they are capable to adsorb on cell surface and accumulate in cells due to cellular uptake mechanisms. Owing to combination of PD and cell uptake advantages, BSA-PS NPs demonstrated higher efficacy of photodynamic damage to cancer cells as compared to free PS at equivalent concentrations. These results suggest that non-targeted BSA-PS NPs with high PD activity and low-fabrication costs of are promising candidates for transfer to PD clinic treatments.

To assess the effectiveness of plasmonic photothermal therapy (PPT) multiple intravenous strategy of gold nanorods (GNRs) administration was used before laser exposure. The model of alveolar liver cancer PC-1 was used in male outbred albino rats, which were intravenously administrated by single and multiple injections of GNRs and then were treated by PPT. The gold dosage was 400 μg (single injection group), 800 μg (double injection group), 1200 μg (triple injection group), and absorption maximum of gold nanorods suspension was at the wavelength of 808 nm. 24 hours after last injection the tumors were irradiated by the 808-nm diode laser during 15 min at power density 2.3 W/cm². Temperature control of the tumor heating was provided by IR imager. 24 hours after the PPT the half of animals from each group was withdrawn from the experiments and the sampling tumor tissue for morphological study was performed. In survived animals the growth of tumors was evaluated during 21 days after the PPT. The antitumor effects of PPT after triple intravenous injection were comparable with those obtained at direct intratumoral administration of similar total dose of GNRs. The effectiveness of PPT depended on gold accumulation in tumor, probably, due to sufficient vascularization of tumor tissue.

Functionalized nanoparticles are important analytical tool for biomedical applications. Pulsed laser ablation of bulk targets in an aqueous media is the one-step method for the fabrication, size manipulation and biofunctionalization of nanoparticles. We performed kHz laser ablation of a silver target by nanosecond pulses in tetramethylammonium hydroxide (TMAH) and sodium dodecyl sulfate (SDS) aqueous solutions to prepare silver nanoparticles. It was shown that the formation efficiency was increased by addition of TMAH and SDS as well as the stability of nanoparticles. The size decrease of the nanoparticles by addition of SDS was more remarkable than in the laser ablation in TMAH aqueous solutions. Emitted nanoparticles interact with TMAH and SDS in the secondary laser irradiation process leads to the nanoparticles stabilization in aqueous solutions.

The article contains description of several demonstration experiments connected with application of light scattering (LS) for investigation of optical properties of nanoparticles solutions. The demonstrations are based on the usage of laser pointers with different wavelengths (405, 532, and 650 nm) for observing of light scattering and absorbance by various nanoparticles (silver, gold, sulfur, and cadmium selenide). These experiments were used during short course for secondary school students ("Introduction to Nanotechnology") and applied as hands-on activities in order to introduce students to methods of investigation of nanostructures. The demonstrations (included to the course) were tested during summer-camp school (in 2015 and 2016) and in club in chemistry (2016) for secondary school students (15–17 years old).

Photonic crystal fibers (PCFs) are one of the most promising materials for biosensors construction due to their unique optical properties. The modification of PCF by noble metal nanoparticles (NPs) provides the SPR and SERS signal detection where as the application amino group-containing compounds allows efficient binding of biomolecules. In this work the internal surface of glass hollow core photonic crystal fibers (HC-PCFs) has been modified Ag and Au nanoparticles using three different approaches. PCFs were treated by: 1) mixture of NPs and precursors for silanization (tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)); 2) alternately deposition of polyelectrolytes and NPs, 3) mixture of chitosan with NPs. The shift of local maxima in the HC-PCF transmission spectrum has been selected as a signal for estimating the amount of NPs on the HC-PCF inner surface. The most efficient techniques were the chitosan application for Ag NPs and silanization for Au NPs. The obtaining PCFs could be useful for creating biosensitive elements.

In vivo optical trapping is a novel applied direction of an optical manipulation, which enables one to noninvasive measurement of mechanical properties of cells and tissues in living animals directly. But an application area of this direction is limited because strong scattering of many biological tissues. An optical clearing enables one to decrease the scattering and therefore increase a depth of light penetration, decrease a distortion of light beam, improve a resolution in imaging applications. Now novel methods had appeared for a measurement an optical clearing degree at a cellular level. But these methods aren’t applicable in vivo. In this paper we present novel measurement method of estimate of the optical clearing, which are based on a measurement of optical trap stiffness. Our method may be applicable in vivo.

Fluorescent angiography approach in application to a living chicken embryo is discussed. It provides precise vessel wall detection and demonstrates usefulness for real time monitoring of vasoconstriction and vasodilatation related to self regulation of vascular network as well as to response to external factors. On the other hand, high stability of fluorescence and long period of dye elimination makes variations of fluorescent intensity practically independent from fast variations of blood flow rate. Therefore, we proposed the improvement of fluorescent angiography technique by introduction of photobleaching fluorescent velocimetry approach. We have developed the imaging system for intravital microscopic photobleaching velocimetry and tested it by using a glass capillary tube as a model of blood vessel. We demonstrated high potential of the technique for instant flow velocity distribution profile measurement with high spatial and temporal resolution up to 2 μm and 60 ms, respectively.

We present adaptive micro-scale Particle Image Velocimetry (μPIV) technique for visualization of the capillary network blood flow microcirculation. The main idea of our method is a centering of the interrogation regions (IR) of the μPIV technique via capillary network masks. These masks were obtained by the algorithm of Niblack local binarization of the capillary network images for the each frame. Due to the inhomogeneous of red blood cells (RBCs) distribution, we have summarized the masks across a whole series of masks. The blood flow velocity map was measured within the limits of the resulting the mask. We illustrate step-by-step the blood flow velocity measurement method and we reconstruct velocity map for chorioallantoic membrane (CAM) of chicken embryo.

Influence of flavonoids on the intensity of peroxidation processes in the blood is investigated by numerical modeling and by experiment in vivo. As an example we consider the effects of flavonoid-containing extract of Helichrysum arenarium L. with antitumor activity on serum of rats with transplanted liver cancer PC-1. It was found that the content of malondialdehyde, lipid hydroperoxides and average mass molecules were decreased in animals with transplanted liver cancer after intramuscular and oral administration of Helichrysum arenarium L extract in a dose of 1000 mg/mL. The extract reduces the intensity of lipid peroxidation processes in animals. The compound formation possibility of flavonoids and products of lipid peroxidation is investigated by numerical simulations. Using the density functional theory method of molecular modeling, we analyze hydrogen bonds formation and their influence on IR - spectra and structure of molecular complex which is formed due to interaction between flavonoids and products of lipid peroxidation processes on example of naringine and malondialdehyde. We have found that naringine can form a steady molecular complex with malondialdehyde by hydrogen bonds formation. Thus, the application of Helichrysum arenarium L. extract for suppression processes of lipid peroxidation and activation of enzymatic and non-enzymatic antioxidant systems is promising.

The regularities of movement of the Photon Density Normalized Maximum (PDNM) in highly scattering media such as biological tissues are described. An improved model of the optical properties of turbid media based on the diffusion approximation to the Radiative Transfer Equation (RTE) is used for identifying regularities of PDNM movement. Numerical simulations confirmed that in homogeneous cylindrical objects PDNM always moves to the geometric centre of the object. In the case of single absorbing inhomogeneities PDNM moves towards the point which is symmetrical to the geometric centre of it with respect to the center of the object. In the presence of a single scattering inhomogeneity PDNM moves towards its geometric centre.

A method of optical coherence tomography (OCT) structural images reconstruction using Monte Carlo simulations is described. Biological object is considered as a set of 3D elements that allow simulation of media, structure of which cannot be described analytically. Each voxel is characterized by its refractive index and anisotropy parameter, scattering and absorption coefficients. B-scans of the inner structure are used to reconstruct a simulated image instead of analytical representation of the boundary geometry. Henye-Greenstein scattering function, Beer-Lambert-Bouguer law and Fresnel equations are used for photon transport description. Efficiency of the described technique is checked by the comparison of the simulated and experimentally acquired A-scans.

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%-Omnipaque^TM(300) solution and Omnipaque^TM (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.

In this work we studied the efficiency of spatially modulated illumination in optical diffuse reflectometry (ODR) and analyzed various probing patterns. The optimal illumination pattern was determined from the series of Monte Carlo numerical experiments on structured illumination and comparison of the parameters of fluence distribution within tissue. We considered the following illumination profiles: sinusoidal patterns with different spatial frequencies k (1 - 2.5 mm-1); piecewise constant patterns with the fixed duty cycle w = 2 and various strip width (0.2 – 1 mm); piecewise constant patterns with the fixed strip width (0.1 mm) and various duty cycle (3 – 11). Assuming the same total incident intensity for all patterns, we observed the growth in intensity at depth with decreasing value of spatial frequency for sinusoidal pattern, the similar tendency of intensity distribution was for piecewise constant patterns with the fixed strip width (or duty cycle) and duty cycle increase (or increase of a strip width, respectively). The intensity distributions within the sample are almost identical for sinusoidal and piecewise constant patterns with matching peaks and lows. However, probing by piecewise constant profile of illumination provide more local information about sample’s properties. A prototype of an ODR system for probing with the structured illumination was designed. The system consists of PC-controlled optical projection system, polarization filters and a CCD camera. The approbation of the system was carried out on the optical phantoms with optical properties close to those of biological tissues and on skin of human volunteers.

This work is devoted to investigation of optical properties (dispersion of refractive index, permittivity and absorption coefficient) of human nails in THz frequency range. These data were obtained by THz time-domain spectroscopy (TDS) technique in transmission mode. These results may be used to develop non-invasive technique of human pathologies control using nail as reference sample in reflection mode of THz TDS.

The aim of this report is detection of model compound, rhodamine 6G (R6G), in blood and urine samples using surfaceenhanced Raman spectroscopy (SERS) as a detection tool and liquid-liquid extraction (LLE) for improving quality of SERS analysis (SERS-LLE combination). SERS substrate is a plasmonic nanomaterial which possesses drastic increasing of Raman spectrum intensity (10⁶‒10⁸) of any molecule adsorbed onto its surface. Here we used citrate stabilized silver nanoparticles as SERS substrate and synthesized them applying wet chemical approach. Before SERS measurements, blood and urine samples were artificially contaminated with R6G using 50 and 500 ng/mL concentrations for both samples. In order to reduce detectable concentrations of R6G and improve signal-to-noise ratio, we applied LLE which allows us to separate R6G from the matrix mixture and increase the analyte concentration. Four different LLE protocols were used and the most efficient one was found. Obtained results showed usefulness of SERS-LLE combination for chemical analysis of body fluids with level of detectable concentration down to tens ng/mL.

Upconversion nanoparticles are good candidates for nanothermometry. The wavelength of the excitation and luminescence lie in optical window. The influence of the excitation power density on the luminescence temperature dependences is studded. Ratio of luminescence intensities linearly depends on temperature.

This article is dedicated to synthesis of aqueous solutions of nanoparticles based on rosin. Dependence of colloidal stability of rosin nanoparticles (RNP) on different factors (such as pH, solvent nature, and temperature) were investigated and discussed. Obtained RNP samples were characterized by dynamic light scattering, UV-visible absorbance spectroscopy, and scanning electron microscopy. It was found that RNP usually have size in the range 100‒200 nm with a maximal stability at neutral pH which is caused by relatively high surface charge of RNP (‒40 mV). Acidic media leads to fast precipitation of RNP, while alkali one leads to complete dissolution of the RNP due to formation of abietates (abietic acid is the main component of rosin).

Phantoms are an imitation of biological tissue, which are physically modeling the propagation of light in biological tissues. They are required for different purposes, and also repeatability of results is achieved with it. So the fabrication of solid tissue phantoms containing high absorb or luminescence nanoparticles is actual problems for experimenters. The work describes fabrication processing and characteristics of solid tissue phantoms.

We obtained impedance dispersion curves of stomach and liver tissues of rats in dynamics, while affecting with tumorigenic inductors: sodium nitrite (0.2%) and m-toluidine (25 mg per 1 kg body weight) in chronic experiment (over 10 months) in male outbred white rats aged 3 and 14 months at the beginning of the experiment. A substantial decrease in the impedance values for all test frequencies (50 Hz to 1 MHz) was shown.

Speckle correlometry gives the possibilities to visualize tissue scattering structure analyzing the correlation characteristics of speckle-modulated images. In this work, the inhomogeneous multiple scattering medium with the "dynamic" long inclusions was investigated like a blood vessels in living tissue. The scattering media is 0.28% weight fraction of gelatin dissolved in water and 1 gram per liter (gL^-1) and 100 mg per liter (gL^-1) of TiO₂ for optical scattering. The movement of fluid (distilled water) in the cylindrical hole with given radius simulate a blood motion in the vessel. It was shown the possibility to determinate the depth location of dynamic inhomogeneities inside a scattering medium.

Non-linear properties of titania nanoparticles were studied using the closed aperture z-scanning with the simultaneous measurements of the intensity of Rayleigh scattering. Pulsed laser light at 355 nm was applied as the probe radiation. The intensity of probe beam in the waist plane of a focusing lens was varied in the range from 5⋅10⁶ W/cm² to 1.1⋅10¹¹ W/cm². Water suspensions of 25 nm titania nanoparticles were used as the studied samples. The obtained values of nonlinear extinction and scattering intensity were used to retrieve the real and imaginary parts of the effective dielectric function of nanoparticles in the dependence on the pumping intensity. It was found that the real part of the effective dielectric function becomes negative at the pumping intensities exceeding ≈ 7⋅10⁸ W/cm². However, the effect of resonance excitation of localized surface modes does not occur due to very high values of the imaginary part in this case.

The results of experimental study of the foam structure evolution at various temperatures using correlation analysis of backscattered laser light are presented. Shaving foam was used for preparation of the phantom samples. It was found that for the later stages of structure evolution the significant spread of the local estimates of intensity correlation time is characteristic. This feature is interpreted in terms of the increasing probability for burst-like processes associated with local changes in the bubble configurations. The statistics of the local estimates of intensity correlation time is analyzed. The possible contribution of the sampling volume effect on the observed fluctuations of the correlation time is considered using the results of Monte-Carlo simulations of probed light transport in the medium.

Random changes in the polarization states of partial contributions to the multiple scattered light fields in a random medium are analyzed using the statistical modeling of polarized light transport in the medium. The mapping of local polarization states on the Poincaré sphere surface clearly indicates the different scenarios of the "order – disorder" transition in the case of Rayleigh and Mie scatterers. If the random medium consisting of small particles is probed by a linearly polarized laser beam, then propagating partial waves keep their linear polarization state but the dispersion of azimuth angles rapidly increases with the increasing average propagation path for these waves. On the contrary, the multiple scattering by random ensembles of the large particles is accompanied by random transformations of the linear polarization of propagating waves to the elliptical polarization. The obtained results are considered in the relation to the known features of polarization decay in the random media.

Statistical properties of speckles obtained using a narrow-band spectral selection of fluorescence from a coarse-grained dye-doped medium were experimentally studied. Silica powder doped by Rhodamine 6G solution and pumped by CW laser radiation at 532 nm was used as the sample medium. It was found that the speckle contrast falls down with an increasing fluorescence yield and rises up to the values close to the characteristic value for the Rayleigh distribution of speckle intensity at the edges of emission spectrum. This effect was interpreted in terms of the relationship between a path length distribution of fluorescence and its spectral decorrelation.