Significance:Preparation of a recipient cytoplast by oocyte enucleation is an essential task for animal cloning and assisted reproductive technologies in humans. The femtosecond laser is a precise and low-invasive tool for oocyte enucleation, and it should be an appropriate alternative to traditional enucleation by a microneedle aspiration. However, until recently, the laser enucleation was performed only with applying a fluorescent dye. Aim:This work is aimed to (1) achieve femtosecond laser oocyte enucleation without applying a fluorescent dye and (2) to study the effect of laser destruction of chromosomes on the structure and dynamics of the spindle. Approach:We applied polarized light microscopy for spindle visualization and performed stain-free mouse and human oocyte enucleation with a 1033 nm femtosecond laser. Also, we studied transformation of a spindle after metaphase plate elimination by a confocal microscopy. Results:We demonstrated a fundamental possibility of inactivating the metaphase plate in mouse and human oocytes by 1033 nm femtosecond laser radiation without applying a fluorescent dye. Irradiation of the spindle area, visualized by polarized light microscopy, resulted in partly or complete metaphase plate destruction but avoided the microtubules impairment. After the metaphase plate elimination, the spindle reorganized, however, it was not a complete depolymerization. Conclusions:This method of recipient cytoplast preparation is expected to be useful for animal cloning and assisted reproductive technologies.

It is known that during the process of aging, there is a significant decrease in the number of melanosomes in the retinal pigment epithelium (RPE) cells in the human eye. Melanosomes act as screening pigments in RPE cells and are fundamentally important for protection against the free radicals generated by light. A loss or change in the quality of melanin in melanosomes can lead to the development of senile pathologies and aggravation in the development of various retinal diseases. We have previously shown that the interaction between melanin melanosomes and superoxide radicals results in oxidative degradation with the formation of water-soluble fluorescent products. In the present study, we show, using fluorescence analysis, HPLC, and mass spectrometry, that visible light irradiation on melanolipofuscin granules isolated from RPE cells in the human eye results in the formation of water-soluble fluorescent products from oxidative degradation of melanin, which was in contrast to lipofuscin granules and melanosomes irradiation. The formation of these products occurs as a result of the oxidative degradation of melanin by superoxide radicals, which are generated by the lipofuscin part of the melanolipofuscin granule. We identified these products both in the composition of melanolipofuscin granules irradiated with visible light and in the composition of melanosomes that were not irradiated but were, instead, oxidized by superoxide radicals. In the melanolipofuscin granules irradiated by visible light, ions that could be associated with melanin oxidative degradation products were identified by applying the principal component analysis of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) data. Degradation of the intact melanosomes by visible light is also possible; however, this requires significantly higher irradiation intensities than for melanolipofuscin granules. It is concluded that the decrease in the concentration of melanin in RPE cells in the human eye with age is due to its oxidative degradation by reactive oxygen species generated by lipofuscin, as part of the melanolipofuscin granules, under the action of light.

Transient absorption spectroscopy, kinetics of absorption anisotropy decay for bis-aza-18-crown-6-containing di-benzylidenecyclobutanone dye and its metal complexes, and quantum chemical calculations support the presence of the first stage in the photorecoordination mechanism for the complexes with the Ba2+, Ca2+, and K+ cations. The depolarization parameters, including the radii of solvates, are deduced from the experimental data. During the barrierless photorecoordination of the complex with two Ba2+ cations, the solvent shell of the crowned Ba2+ cation undergoes the following changes: (2 + 1)MeCN, (3 + 1)MeCN, 4 MeCN.

To assess the prospects for using intense femtosecond laser radiation in biomedicine, it is necessary to understand the mechanisms of its action on biological macromolecules, especially on the informational macromolecule—DNA. The aim of this work was to study the immunocytochemical localization of DNA repair protein foci (XRCC1 and γH2AX) induced by tightly focused femtosecond laser radiation in human cancer A549 cells. The results showed that no XRCC1 or γH2AX foci tracks were observed 30 min after cell irradiation with femtosecond pulses of 1011 W∙cm−2 peak power density. An increase in the pulse power density to 2 × 1011 W∙cm−2 led to the formation of linear tracks consisting both of XRCC1 and γH2AX protein foci localized in the places where the laser beam passed through the cell nuclei. A further increase in the pulse power density to 4 × 1011 W∙cm−2 led to the appearance of nuclei with total immunocytochemical staining for XRCC1 and γH2AX on the path of the laser beam. Thus, femtosecond laser radiation can be considered as a tool for local ionization of biological material, and this ionization will lead to similar effects obtained using ionizing radiation.

A new type of pyropheophorbide-fullerene[60] dyad was synthesized by their attachment by the cyclopropane backbone at the 13(1)-position of the chlorin macrocycle using the Hummelen-Wudl method. Here we report a complex analysis of the structure influence on the photophysical properties of the newly obtained dyad and its comparison with another pyropheophorbide-fullerene[60] dyad. The latter dyad was previously obtained by the attachment of the tetrahydropyrrole backbone at the third position of the macrocycle using the Prato reaction. It was shown by quantum-chemical modeling that the studied dyads have drastically different spatial positions of the fullerene core relative to the dye macrocycle plane: "parallel" for the former and "perpendicular" - for the latter. The influence of structural differences on various properties of dyads was studied: the aggregation properties, absorption spectra, the fluorescence quenching of the dye moiety in the dyads, and the lifetimes of excited states. The data obtained are important for the further development of methods for the directional design of the photoactive fullerene-dye structures - highly effective photosensitizers for photodynamic therapy.

A series of DMABN‐related compounds with two‐band fluorescence was studied by steady‐state absorption and fluorescence spectroscopy, time‐resolved absorption spectroscopy upon excitation with a 30‐fs laser pulse, and by TDDFT and xMCQDPT2 quantum chemical methods. The efficiency of the intramolecular electron transfer was found to depend on the excitation wavelength in MeCN. The reaction is described by a two‐state scheme (LE↔CT); the Stevens‐Ban method gives underestimated values for the reaction enthalpy ΔH (SB). The spectral luminescence and kinetic parameters, rate constants, and barriers for the forward (k1, Ea) and reverse (k−1, Ed) electron transfer were calculated. The Marcus plot for k1 versus the driving force (−ΔG) and the total reorganization energy (λ) were calculated for six compounds. It was shown that without a barrier, the 1/k1 value (267 fs) is close to the mean solvation time in MeCN (260 fs), ie, the reaction rate is completely determined by the solvent. The results of conformational analysis for all studied compounds are consistent with the twisted intramolecular charge transfer model of structural relaxation.

Biexcitons localized at ZnxCd1−xS quantum dots (x = 0.37 or 0.45) with a diameter of ~ 45 Å synthesized by two different methods were studied by femtosecond laser spectroscopy. The spectral features of ultrafast transient absorption spectra at the short-time delay of 70 fs are associated with the three lowest energy transitions of quantum dots. The shapes of the transient absorption bands were modeled by fitting to linear absorption. The spectral positions of the absorption components of the excited state in the transient spectra take into account the energy of the biexciton coupling. By fitting the experimental transient absorption spectra of ZnxCd1−xS QDs, the binding energies of biexcitons were determined. The biexciton binding energies vary from 16.6 to 37 meV depending on the biexciton transition excited at the ZnxCd1−xS quantum dot.

We report the effect of laser cavitation in water initiated by femtosecond pulses confined into subwavelength volume of photonic nanojet of spherical microparticles. The effect of nanoscale optical breakdown was employed for controllable and nondestructive micromanipulation of silica microspheres. We combine this technique with optical trapping for cyclic particle movements and estimate a peak velocity and an acceleration acquired by microspheres propelled by nanojet cavitation. Our study provides a strategy for nondestructive optical micromanipulation, cavitation-assisted drug delivery, and laser energy transduction in microdevices.

An intramolecular tautomeric fluorescent BODIPY sensor has been designed and synthesized. The obtained BODIPY dye is a combination of the 4-bora-3a,4a-diaza-s-indacene core and a diketone fragment. The study of conformational equilibria in the ground and excited states has been completed for a broad range of solvent polarity by steady state and NMR methods as well as by DFT and TD-DFT calculations. The interpretation of the unique emission observed in hydrogen bond accepting solvents upon the excitation of the fluorescent dye in the S-0-S-2 transition has been accomplished. The Jablonski diagram has been analyzed for the observed processes in the BODIPY dye studied on the basis of DFT and TD-DFT calculations.

Owning to excellent optical properties and high biocompatibility carbon dots (CDs) have drawn increasing attention and have been widely applied as imaging agents for various bio-applications. Here we report a strategy for live-cell fluorescent bioimaging based on in situ synthesis of CDs within cells by tightly focused femtosecond laser pulses. Laser-produced carbon dots exhibit bright excitation-dependent fluorescence and are highly two-photon active under near infrared femtosecond excitation, thus demonstrating a potential for two-photon fluorescence imaging. The Raman spectra of fluorescent centers show strong D (1350 cm-1) and G (1590 cm-1) bands, thus suggesting that they are composed of carbon dots with sp2-hybridized core. Using Mouse GV oocytes as a model system we examine cytotoxicity and demonstrate the possibility of long-term fluorescent intracellular tracking of the laser-produced CDs. Created virtually in any point of the live cell, CD-based fluorescent μm-sized markers demonstrate high structural stability and retain bright fluorescence many hours after formation. Our results point to laser-produced fluorescent CDs as a highly-potent tool for cell cycle tracking, culture cell marking and probing intracellular movements.

The effect of the laser pulse energy and total expose of the energy incident on the embryo blastomere fusion probability was investigated. The probability of the four different events after laser pulse was determined: the fusion of two blastomeres with the following formation of tetraploid embryo, the destruction of the first blastomere occurs, the second blastomere conservation remains intact, the destruction and the death of both cells; two blastomeres were not fused, and no morphological changes occurred. We report on viability and quality of the embryo after laser surgery as a function of the laser energy incident. To characterize embryo quality, the probability of the blastocyst stage achievement was estimated and the blastocyst cells number was calculated. Blastocoel formation is the only event of morphogenesis in the preimplantation development of mammals, so we assumed it as an indicator of the time of embryonic “clocks” and observed it among fused and control embryos. The blastocoel formation time is the same for fused and control embryos. It indicates that embryo clocks were not affected due to blastomere fusion. Thus, the analysis of the fluorescence microscopic images of nuclei in the fused embryo revealed that nuclei fusion does not occur after blastomere fusion.

The complex formation of bis(18-crown-6) stilbene (1) and its supramolecular donor-acceptor complex with N, N'-bis(ammonioethyl) 1,2-di(4-pyridyl)ethylene-derivative (2) with alkali and alkaline-earth metal perchlorates has been studied using absorption, steady-state fluorescence, and femtosecond transient absorption spectroscopy. The formation of 1M(n+) and 1(Mn+)(2) complexes in acetonitrile was demonstrated. The weak long-wavelength charge-transfer absorption band of 1.2 completely vanishes upon complexation with metal cations because of disruption of the pseudocyclic structure. The spectroscopic and luminescence parameters, stability constants, and 2-stage dissociation constants were calculated. The initial stage of a recoordination process was found in the excited complexes 1M(+) and 1(M+)(2) (M = Li, Na). The pronounced fluorescence quenching of 1.2 is explained by very fast back electron transfer (tau(et) = 0.397 ps). The structure of complex 1.2 was studied by X-ray diffraction; stacked (1.2)(m) polymer in which the components were connected by hydrogen bonding and stacking was found in the crystal. These compounds can be considered as novel optical molecular sensors for alkali and alkaline-earth metal cations.

Complexation between two aza-15-crown-5 ethers bearing electron donor and acceptor fragments and alkali and alkaline earth perchlorates has been studied using absorption, steady-state fluorescence and femtosecond transient absorption spectroscopy. The spectral-luminescent parameters, the stability and dissociation constants of the complexes were calculated. The intramolecular charge transfer reaction takes place both in the excited state of the crowns and their complexes 1:1; the latter is subjected to photorecoordination resulting in a weakening or a complete disruption of coordination bond between nitrogen atom and metal cation, disposed within a cavity of the crown. The compounds investigated can be viewed as novel optical molecular sensors for alkali and alkaline-earth metal cations. The photoejection of a metal cation into the bulk was not observed.

A comparative evaluation of the antibacterial effect of silver in the form of nanoparticles and Ag+ ions was performed. Silver nanoparticulate coatings of stable and reproducible morphology were prepared on monolayer size-selected titanium-oxo-alkoxy nanoparticles deposited on glass substrates. The coatings exhibit a strong antibacterial activity towards Escherichia coli K12 AB 1157 and suppress biofilms formation. This activity is mainly related to the Ag+ ions release into aqueous solutions in dark. The deposited silver mass ~1 μ g.cm-2 is smaller compared to that of Ag+ ions and nanoparticles generally reported for inhibiting Escherichia coli. The synergetic effect of the deposited nanoparticles and Ag+ ions can be suggested.

A new approach for fabricating a range of patterns using femtosecond optical trap-assisted nanopatterning is presented. We report how a single Gaussian laser beam from a 55 fs, 80 MHz, 780 nm Ti:sapphire oscillator trapping dielectric microspheres near surfaces can be used to enable near-field, direct-write, subwavelength similar to lambda/6 (similar to 130 nm), two-dimensional nanopatterning of a polymer surface. We discuss the stability conditions for effective manipulation of the particle by the pulsed beam. Klein-Kramers and Brownian motion models were used to analyze the positional accuracy of femtosecond tweezers. We studied effects of the microsphere size, pulsed laser energy and light polarization, and spacing between objective focal plane and polymer surface on the pattern size experimentally and theoretically. Microspheres with a diameter of about 1 mu m provide the smallest patterns. The experimental results are reasonably matched by generalized Lorentz-Mie theory.

We report on a new method of preparation of Ag-N-TiO2 nanoparticulate coatings with stable and highly reproducible morphology. The silver nanoparticles are grown on monolayer titanium-oxo-alkoxy nanoparticulate coatings by silver ions reduction at UV-A light illumination. Their size and surface number density increase with the irradiation time. The AFM and high-resolution SEM and TEM measurements of height (h) and lateral size (D) of the silver nanoparticles show that their shape approaches spherical segment with h/D = 1/4 at long irradiation times. The size correspondent to the maximum of the particles size distribution curve tends to D = 12 nm with half width at full-maximum Delta D = 4 nm. The evaluation of the deposited silver mass results in the quantum yield of the deposition process close to 100% at the process beginning and the atomic surface density of N-Ag = 1 25 x 10(7) at/mu m(2) at the process saturation. The absorption spectra of the surface plasmon shift from 425 to 525 nm. The spectra are successfully modeled assuming small dispersion of the oblate particle shape asymmetry Delta(h/D) approximate to 0.25 and surface number density below 2500 part/mu m(2). Mutual interaction between the silver particles is shown to weakly affect the spectra. Two-photon photoluminescence images of the composite nanocoatings show the characteristic hot-spot pattern of surface plasmons.

We report mode locking in a Ti:sapphire (Ti:Sa) laser at the wavelength of 810nm using a polymer film with single-walled carbon nanotubes (SWNTs) applied as a saturable absorber. Pulses with 600fs duration and 0.4nJ energy were generated from the Ti:Sa laser with polymer-SWNT composite film for cw passive mode locking.

Nonlinear optical absorption of single-wall carbon nanotubes in carboxymethylcellulose (CMC) thin polymer film has been studied by the Z-scan method. Nonlinear saturated absorption at lambda=1080 nm was registered with saturation intensity of 170 MW/cm(2). Ultrashort pulses with duration of 3 ps were generated at lambda=1055 nm using this composite polymer film as a saturable absorber for passive mode locking in a neodymium glass laser.

The clathrochelate di- and tri-ribbed-functionalized ruthenium(II) tris-dioximates with alkylamine, thioaryl, thioalkyl, phenoxyl, and crown ether substituents in α-dioximate fragments have been synthesized starting from reactive hexachloride clathrochelate precursors, formed by cross-linking with phenyl-, n-butyl- and fluoro-boronic capping groups. The IR, UV-vis, 1H, 13C NMR and luminescent spectra as well as X-ray data for complexes obtained have been discussed. The redox characteristics (from cyclic voltammograms) for ruthenium(II) clathrochelates have been correlated with the electrochemical parameters of the corresponding iron(II) complexes and σpara constants for functionalizing substituents.