ზაზა მელიქიშვილი

Photoplethysmography (PPG) is a photometric technique which is widely used in the detection of time-dependent blood volume changes in the peripheral tissues of the body. Despite the long history of research, the detailed mechanism of this phenomenon is still a matter of debates. This applies to such important body locations as the projection of the radial artery on the wrist. Based on the above, our goal is to determine the mechanism of the PPG-signal formation at this particular location. In this paper, we analyze a series of observations obtained using reflection-mode PPG. In our experiments, photoplethysmograms were recorded in the wavelength range of 400 – 1000 nm (with a step of 1 nm). Recordings were made for 10 s and the time step was 16.5 ms. Measurements were carried out in vivo on the projection of the radial artery of the wrist. The observed photoplethysmograms are described by modification of the physiological model of the interaction of light with living tissue proposed several years ago. This model provides a reasonable explanation for all observations. According to this model, it is the pulsating transmural pressure of the radial artery that increases/decreases the density of capillaries in the dermis, thereby modulating the volume of blood in the capillary bed. The photoplethysmogram observed in the green/blue range of the optical spectrum was due to modulation of the blood volume in the capillary bed. In the yellow-red and near infrared ranges, the PPG signal was a modulated blood volume in the capillary bed and artery. For these ranges, differences in the PPG signal shapes are not observed. Differences are observed only in intensities, which is proportional to the amount of blood in the area of interaction. The PPG signal is also modulated by the respiratory rate.

The goal of the present work is the study of γ-irradiation (Cs137) on conformation of DNA double helix in NaCl and NaNO3 solutions. The observed bathochromic shift of DNA absorption band of 90 cm-1 and widening of the band by 240 cm-1 allows us to consider that GC base pairs in DNA –NaCl solution compared to DNA – NaNO3 solution show greater amount of wrong Watson–Crick GC pairs than NaNO3 solution due to double proton transfer (DPT). It is even better shown by the effectivity of energy transfer. In NaCl solution the efficiency of energy transfer, EET= 0.88, when the same transfer in NaNO3 is 0.67. Effect of γ-irradiation dose of 26.4 kilorad on thymus DNA in 0.01M NaCl and NaNO3 solutions (pH=6) has been studied. DNA concentration was 5.6x10-4 M (P). Total amount of primary products of water radiolysis at neutral pH after 26.4 krad irradiation was nearly 0.38 on a single DNA nucleotide. Under irradiation of DNA in NaCl solution the efficiency of energy transfer, EET, from AO to EB intercalated in double helix is changed from 0.88 to 0.92. Registration of DNA UV absorption spectra at l@260 nm demonstrated distraction of 9% of bases; single strand scissions in DNA-NaCl is one distraction per 100 DNA nucleotides. When ethanol (0.1 M) is present irradiation practically does not distract nucleus bases but causes EET change from 0.82 to 0.89. At DNA irradiation in NaNO3 solution the bases are not distracted but the irradiation induces EET change from 0.65 to 0.78. So, LI FRET spectroscopy applied with UV spectrometry is quite a sensitive method to detect structural defects (stress) of DNA double helix.

The aim of the present work is spectroscopic and spectro-fluorimetric study of DNA catalytic properties in the following processes a) Oxidation; b) Formation of inter-strand cross-links; c) Fluorescence resonance energy transfer (FRET). Using spectroscopic and spectro-fluorimetric approaches we have shown that at interaction with DNA, silver nanoparticles with the size 1-2 nm (AgNPs) are adsorbed on it and only partial corrosion of nanoparticles at the level of Ag+ ions is observed; AgNPs represent liquid drops which moisture the DNA surface at interaction; it is considered the mechanism of AgNPs corrosion by hydronium while interacting with DNA. It is shown that there is a simultaneous adsorption of H30+ ions and AgNPs on the surface of DNA, which cause the formation of AgNPs.H3O+ complex. As adsorption of H30+ ions on the DNA surface has a mobile character, the possibility for formation of AgNPs.H3O+ complex increases; it is considered the mechanism of inter-strand cross link formation in DNA double helix, induced by Ag+ ions. So, in the case of DNA compound absorption process of interstrand cross-links formation can be reduced to a multi-stage adsorption process consisting of several simple adsorption processes named above with the total time of t1 + t2 + t3.  FRET method allows to estimate the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare various types of DNAs with different origin; various damage degrees and being in various functional state.

The aim of this work is to demonstrate the significance of the phenomena of light re[1]radiation and the electron excitation energy transfer from the donor to the acceptor in the hydrolysis reactions of glycoside and phosphodiester bonds in DNA, which is important for the functionality of cells in the norm and pathology and for the analysis of the quality of the double helix DNA for diagnostic purposes. It is shown that photons of the near-IR region of the spectrum excite the overtones of the large-amplitude valence vibration of water molecules in the 700 – 1500 nm spectral range. This causes the activation of electrolytic dissociation of water molecules with the formation of H+ and OH– , which is necessary for the hydrolysis reaction of chemical bonds in biological molecules. The application of the original nanoscale method of a laser induced fluorescence resonance energy transfer to a donor-acceptor intercalator pair for the quantitative and qualitative study of stability quality DNA double helix in a solution, in real time is shown in the following biologically important processes: photo-irradiation, photodynamic effect and electron excitation energy transfer in strongly scattering environment (colloidal) with multiple scattering of light, i.e. in processes that can be successfully used in light therapy of cancer, dermatology, wound healing, etc.

The goal of this work is using the method of laser - induced fluorescence resonance energy transfer (FRET) of electronic excitation in the donor-acceptor pair of intercalators, (acridine orange as a donor and ethidium bromide as an acceptor), for quantitative analysis of the quality of DNA double helix. The approach allows getting a visual picture of the defects of genetic apparatus of tissue cells, particularly of skin cells in real time and it can be used for diagnosis of skin diseases, also in cosmetology. Transition metal ions such as Cu(II), Cu(I), Ag(I), silver nanoparticles (AgNPs), photo- and thermo effects were used to cause double helix defects in DNA. Concentration of DNA sites, which are applicable for intercalation, after the exposure to Cu(II), Cu(I), Ag(I) ions, AgNPs impact as well as laser irradiation (λ = 457 nm) and temperature, which are applicable for intercalation, were estimated in relative units. The nanoscale FRET method allows estimation of the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare DNA-s of 1) different origin; 2) with various damage degrees; 3) being in various functional state.

The aim of the present work is spectroscopic and thermodynamic study of DNA catalytic properties in the following processes: redox; performing of photo-dynamic effects; nanoscale resonance radiationless electron excitation energy transfer. Using spectrophotometry and thermodynamic approaches we have shown that 1) at interaction with DNA, silver nano particles with the size 1-2 nm (AgNPs) are adsorbed on it and only partial corrosion of nanoparticles at the level of Ag+ ions is observed; 2) ascorbic acid reduces silver ions in ternary complex DNA-Ag+-AgNPs. Thus, AgNPs activate the process of quick reduction of Ag+ ions to silver atoms; 3) at photo-irradiation desorption of silver atoms from the surface of AgNPs takes place. The atoms are first adsorbed on the surface of DNA and then penetrate inside the double helix making prolate stretched structure; 4) kinetic study of photo-desorption makes it possible to determine desorption rate constant and adsorption heat Qa≥80 kJ/mol Ag0 for AgNPs bound with DNA; 5) AgNPs represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs-DNA complex DNA dependant conformational transition takes place due to fast and intensive heating. The nano-scale method of laser induced fluorescence resonance energy transfer (FRET) to donor-acceptor intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution in real time is offered. The approach is based on the example of acridine orange molecule (donor) and ethidium bromide (acceptor) intercalated in DNA.

The goal of present research is the absorption-spectroscopic studies of resonance interaction of silver atoms in different conditions: 1. In silver nanoparticle; 2. Bound to double helix of DNA; 3. In complex with oligodeoxynucleotides (dodecamer d(CGCGAATTCGCG)); 4. Incapsulated in polyamidoamine (PAMAM) of fourth generation G4 (~4 nm); 5. Absorbed by cellophane membrane. It is shown that AgNPs represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs - DNA complex DNA dependant conformational transition takes place due to fast and intensive heating. It is shown also that in the interaction of atoms of silver reduced by ascorbic acid and in photo - desorption of AgNPs DNA double helix serves as a matrix, namely together with the silver atoms forms the rigid one-dimensional periodic structure.

Our aim is to applicate adsorption and sorption characteristics of DNA, PAMAM (Polyami doamine) – dendrimere, cellophane membranes, human hair and cotton fibber in copper and silver ion reduction to atomic state. Based on DNA – silver complex interactions of structures having identical chromophore and hard structure are demonstrated widening of DNA-silver absorption spectra [1]. Interactions of silver ions with DNA are characterized by inter – cross type of links which reduce dynamic properties of double helix and make it harder. The reason for spectrum widening is further condensation of reduced silver ions in clusters and nanoparticles with the size of more than 50 nm.

      1) The aim of the present work is spectroscopic and thermodynamic study of DNA catalytic properties in the following processes: a) redox; b) formation of inter-strand cross-links; c) performing of photodynamic effects; d) nanoscale resonance radiationless electron excitation energy transfer. The most attention is paid to the latter, as truly nanoscale method in its origin. The nanoscale method of laser induced fluorescence resonance energy transfer (FRET) to donor (acridine orange) – acceptor (ethidium bromide) intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution in real time is offered. FRET method allows to estimate the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare various types of DNAs with 1. different origin; 2. various damage degrees; 3. being in various functional states. Alternative model and mechanisms of photodynamic effect on DNA in solutions are proposed. They are based on photoenergy degradation in solutions. The energy activates electrolytic dissociation of water molecules on H3O+ and OH–f and acts as a catalyst for hydrolysis reactions of phosphordiester and glycoside linkages.         2) Soft ions, in particular Cu+, Ag+, Pt++, and Hg++ ions, are able to form the so-called inter-strand crosslinks in DNA. Let’s consider the process in case of Ag+. First, silver ions are adsorbed on DNA major groove (N7G or chelate complex N7G and O6G). At small silver ion concentration on DNA does not cause ejection of AO and EB. On the other hand, silver ions at interaction with DNA induce double proton transfer in GC pair [1]. Chelate complex with silver ions makes it easy to unfold DNA double helix with wrong Watson–Crick GC pair. The work presents electron configuration of GC atom pairs taking part in H-bonds before and after DPT. In the last process Guanine’s atom O6 is in enol form, nitrogen atom N1G is in pyridine state and N3C in pyrole state. After unfolding of double helix in neutral water solution N3C atom cannot keep enol state in a long time and it should transfer into its usual pyridine state. At the same time silver ions can with definite possibility attack nitrogen atoms N1G still existing in pyridine state. During the following folding of double helix inter-cross link formation between N1G* and N3C takes place. In this way the process of inter-cross link formation can be considered as such simple processes as: 1. Silver ion adsorption on DNA (N7G) and double proton transfer of GC pair with the life-time t1, 2. Unfolding of double helix, formation of N1G* – Ag+ binding, HN3C transfer to N3C and formation of link between N1G* – Ag+ – N3C. Total time of the process is t2, 3. DNA folding with formation of stereoscopically distorted double helix with inter-cross links (t3). So, in the case of DNA compound absorption process of inter-cross link formation can be reduced to a multi-stage adsorption process consisting of several simple adsorption processes named above with the total time of t1+t2+t3.          3) The goal of the present research is development and application of laser induced fluorescence excitation energy transfer method to donor–acceptor intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution, in real time. The approach is based on the example of acridine orange molecule (donor) and ethidium bromide (acceptor) intercalated in DNA. Fluorescence resonance energy transfer (FRET) radii were experimentally estimated in background electrolyte solution (0.01 M NaNO3) and proved to be 3.9 ± 0.3 nm and the data are in satisfactory agreement with the theoretically calculated value R0 = 3.5 ± 0.3 nm. Concentration of DNA sites, exposed to Cu(II), Cu(I), Ag(I) ions, AgNPs and temperature, which are applicable for intercalation, were estimated in relative units. FRET method allows estimating the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare DNAs of 1) different origin; 2) with various damage degrees; 3) being in various functional states. 4) Absorption spectra of AgNPs and of the following complexes DNA – AgNO3 – AgNPs, DNA – AgNO3 – AgNPs – AA are presented. It can be seen that AA reduced silver ions in ternary complex DNA – AgNO3 – AgNPs. Thus, AgNPs activate the process of quick reduction of Ag+ ions to silver atoms. Analyzing absorption spectra we can draw the following conclusions: 1) Ag+ ions interfere in H3O+ ion mobility and prevent oxidation of AgNPs, and 2) AgNPs in their turn activate the process of Ag+ ions reduction in the presence of AA. AgNPs absorption spectra shift to red side (6 – 7 nm) and significant increase of absorption spectra intensity undoubtedly point out the increase of AgNPs size in the complex with DNA. It should be underlined that without DNA nothing happens to AgNPs in water solution. Besides, silver-encapsulated PAMAM dendrimers which are stable nano-size complexes easily saluted in water and lipids, were created and investigated by spectroscopic and thermodynamic methods. They have strong absorption in active spectral areas used in phototherapy and bionanophotonics.

წარმოდგენილია მრავალმიზნობრივი, კომპაქტური, პრეცესიული, მობილური, მცირე ენერგომოხმარებიანი (უმრავლესი გაზომვების ჩატარება შესაძლებელია საავტომობილო აკუმულატორის საშუალებით) ოპტიკური დანადგარი, რომელსაც არ სჭირდება დიდი ფინანსური დანახარჯები.

Application of 1 – 2 nm silver nano-particles (AgNPs) in photo-chemo and photo-thermo therapy of dermal diseases is motivated by their strong light absorption at λ = 430 nm. The goal of the present investigation is to study the interaction of AgNPs with thymus DNA by traditional and original spectra-photometric and thermo-dynamic methods and approaches in darkness and under photo-irradiation. 1) At the interaction of DNA with nano-particles hypsochromic shift of 6 nm and hypochromic effect of 20 % of AgNPs absorption band are observed. 2) At photo-irradiation (λ = 436 nm or full spectrum of visible band) of AgNPs – DNA complexes absorption spectra band width is changed from 140 to 360 nm at half-height. Besides, isosbestic point is observed. 3) Kinetic study of photo-diffusion has made it possible to determine desorption rate constant and desorption reaction activation energy that are equal respectively to k d ≅ 9 • 10–5 s–1 , E d ≅ 80 kJ / mol Ag0 , for AgNPs bound with DNA. It is shown that AgNPs represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs – DNA complex DNA dependant conformational transition takes place due to fast and intensive heating.

By spectroscopic and microcalorimetric methods we have studied the interaction of AgNPs with DNA macromolecules in various environment conditions (ionic strength, dielectrical penetrability, temperature and photo-irradiation). Toxicity of AgNPs in chemo- and photo-chemo-therapy is discussed based on the example of DNA macromolecule. It is sown that photo-irradiation, heating (100 grad C), interaction with denaturized DNA and ethanol leads to the decomposition of nanoparticles to atoms and even ions.The strong toxicity means cell distruction and can serve as a potetial medical treatment for healing cancer.

Using spectrophotometry and spectrofluorometry we have shown that (i) AgNP interactin wth DNA is adsorbed on it and only particle corosion of nanoparticles at the level of Ag+ ions is observed; (ii) At photoirradiaton (436 nm) desorption of silver atoms from the surfaces of AgNP takes place. the atoms are first adsorbed on the surface of DNA and then penetrate inside the double helix making prolate stretch structure; (iii) Kinetic study of photo-desorption has made it possible to determine desorption velocity constant Kd and adsorption heat Qa that are equal to Kd=5.5 +- 0.2 x 10 -4 s-1; Qa>=18.2 kcal / M Ar0 for free AgNP and Kd= 8.9+-0.5 x 10-5 s-1 ; Qa>=19.3 k cal / M Ag0 for AgNP bound with DNA; (iv) On the example of DNA the toxicity of AgNP was been concidered at its application in photo-chemo and photo-thermotherapy of cancer.

1) By spectroscopic and microcalorimetric methods we have studied the interaction of AgNPs with DNA macromolecules in various environment conditions (ionic strength, dielectrical penetrability, temperature and photo-irradiation). Toxicity of AgNPs in chemo- and photo-chemo-therapy is discussed based on the example of DNA macromolecule. It is sown that photo-irradiation, heating (100 grad C), interaction with denaturized DNA and ethanol leads to the decomposition of nanoparticles to atoms and even ions.The strong toxicity means cell distruction and can serve as a potetial medical treatment for healing cancer; 2) Using spectrophotometry and spectrofluorometry we have shown that (i) AgNP interactin wth DNA is adsorbed on it and only particle corosion of nanoparticles at the level of Ag+ ions is observed; (ii) At photoirradiaton (436 nm) desorption of silver atoms from the surfaces of AgNP takes place. the atoms are first adsorbed on the surface of DNA and then penetrate inside the double helix making prolate stretch structure; (iii) Kinetic study of photo-desorption has made it possible to determine desorption velocity constant Kd and adsorption heat Qa that are equal to Kd=5.5 +- 0.2 x 10 -4 s-1; Qa>=18.2 kcal / M Ar0 for free AgNP and Kd= 8.9+-0.5 x 10-5 s-1 ; Qa>=19.3 k cal / M Ag0 for AgNP bound with DNA; (iv) On the example of DNA the toxicity of AgNP was been concidered at its application in photo-chemo and photo-thermotherapy of cancer; 3) წარმოდგენილია მღვრიე, ფლუორესცირებად გარემოში - ბიოლოგიურ ქსოვილში ფლუორესცენციის სპექტრების დაყვანილი ფორმ-ფაქტრორების ანალიზზე დაფუძნებული სამედიცინო დიაგნოსტირების განხორციელების ეფექტური მეთოდი, რომლის მგრძნობელობა და სპეციფიურობა აღემატება 90%. აღწერილია შესაბამისი დანადგარი - ლაბორატორიული ოპტიკურ/ლაზერული ბიოსპექტრომეტრი. 

The aim of this work is to study the interaction of silver nanoparticles (AgNP) with a diameter of 1-2 nm in a direct and indirect way with DNA, acredin orange (AO) and ethidium bromide (EB) molecules in free and intercalated states in DNA. The study of the interaction of AgNP with DNA triple complexes is also presented. Interaction studies are performed by spectrophotometric and fluorometric methods.

In this paper the small angle laser radiation scattering by the biological particles is analyzed. Experimental results and theoretical calculations exhibit that after the ejection from bacteriophage the DNA form the scattering medium consists of quasispherical elements with radius of about 10 x 632 nm.

We present the homemade laser spectrometer. An important part of this spectroscopic system is ultraviolet coherent and non-coherent radiation. It is obtained by converting the fundamental mode of the YAG: Nd3 + laser radiation to the third (by mixing the basic and second harmonics) and the fourth (by doubling the 2nd harmonic) harmonics and the nitrogen laser, while the non-coherent source is YLiF4: Tm3 + system. This range of optical radiation allows to realize the laser-induced and / or non-coherent-source fluorescence of biological objects, which is the most informative method for studying electromagnetic interactions along with other methods of laser / optical spectroscopy. Therefore our UV system is very effective for medical diagnosis.

Absorption and fluorescence spectra, radiative lifetimes and manifold to manifold transitions branching ratios for 1I6, 3P2, and 3P1 multiplets in Tm3+:YLiF4 at the room temperature pointed out the following: 1I6 manifold can serve as upper laser level as effectively as the well known 1D2 and 1G4 levels.

A light scattering and laser-induced fluorescence device built in the laboratory of the Coherent Optics and Electronics Department of the Institute of Cybernetics is presented. The device can study the optical properties of bioobjects in a non-invasive, real-time mode.

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