Alexander A. Skaptsov

Quantitative cell bioimaging using gold-nanoshell conjugates and phage antibodies.

The authors describe a quantitative evaluation of the efficacy of cell labeling with plasmon-resonant light-scattering nanoparticles used as contrast agents for dark-field microscopy imaging. The experimental model is based on the biospecific labeling of pig embryo kidney (SPEV) cells with primary phage antibodies, followed by the dark-field microscopic visualization using conjugates of silica/gold nanoshells with secondary rabbit antiphage antibodies. To quantify nanoparticle binding, the authors introduce the labeling-efficacy factor (LEF) which is equal to the ratio of the bound-particle pixels per cell to the total number of pixels occupied by the cell. The LEF is calculated by an imaging-analysis algorithm based on the freely available ImageJ Java-based processing code. In terms of the LEF, a distinct difference was found between intact, nonspecifically labeled, and biospecifically labeled cells.

THz monitoring of the dehydration of biological tissues affected by hyperosmotic agents

Different ways for monitoring the dehydration of tissues affected by hyperosmotic agents have been comparatively analyzed to increase the THz transparency of biological tissues. The data obtained with an original THz laser spectrometer, a Nicolet 6700 Fourier spectrometer, and a Callegari Soft Plus system for skin diagnostics are in good agreement. The corresponding responses of biological tissues (in the form of THz transmittance, reflectance, absorption coefficient, and hydration coefficient) to the effect of biologically compatible hyperosmotic agents have been studied.

In-vitro terahertz spectroscopy of rat skin under the action of dehydrating agents

In the paper we present the results of study of rat skin and rat subcutaneous tumor under the action of dehydrating agents in terahertz (THz) range (15-30 THz). Frustrated Total Internal Reflection (FTIR) spectra were obtained with infrared Fourier spectrometer Nicolet 6700 and then they were recalculated in the transmittance spectra with Omnic software. Experiments were carried out with healthy and xenografted tumor in skin tissue in vitro. As the dehydrating agents 100% glycerol, 40%-water glucose solution, PEG-600, and propylene glycol were used. To determine the effect of the optical clearing agent (OCA), the alterations of terahertz transmittance for the samples were analyzed. The results have shown that PEG-600 and 40%-glucose water solution are the most effective dehydrating agent. The transmittance of healthy skin after PEG-600 application increased approximately by 6% and the transmittance of tumor tissue after PEG- 600 and 40%-glucose water solution application increased approximately by 8%. Obtained data can be useful for further application of terahertz radiation for tumor diagnostics.

ZnCdS nanoparticles as nanobiosensors to determine denaturation of tissue

The temperature dependence of the fluorescent spectra of ZnCdS nanoparticles placed into a biological tissue has been investigated. It is shown that the fluorescence peak of the nanoparticles is shifted towards longer wavelengths, and fluorescence quenching is observed during heating the biological tissue until its denaturation. ZnCdS nanoparticles are suitable for measuring the temperature of biological nanoobjects under photothermolysis.

Temperature dependence of the fluorescence spectrum of ZnCdS nanoparticles

The temperature sensitivity of the spectral characteristics of ZnCdS nanoparticles both stabilized and coated with polyacrylic acid is compared. It is shown that the luminescence of the nanoparticles has two temperature-dependent parameters, namely, the intensity and the peak position. Variations in these parameters are due to the distortion of the energy states of luminescent surface defects. Aggregation of the nanoparticles does not distort obtained dependencies. Temperature sensitivity is higher for the nanoparticles coated with a layer of polyacrylic acid.

Diagnostic potentialities of plasmon-resonant nanoparticles as contrast agents for the diffuse back scattering spectroscopy of biotissues

The study is aimed at evaluation of diagnostic potential of plasmon-resonant nanoparticles as contrast agents for various techniques based on backward diffuse light scattering from biotissues. We consider the theoretical spectra of diffuse backscattering from a plane layer of gold nanospheres embedded into a plane layer of scattering dielectric spheres that mimic a strongly scattering sample of a biotissue. It is shown that the backscattering spectra contain information about 35-nm gold spheres provided the location depth is less than 600 mkm. The simulated color characteristics resemble the measured characteristics of a rat skin. The measured diffuse reflection spectra of 35-nm gold colloid are close to the spectra of 70/15-nm silica/gold nanoshells although the plasmon resonance wavelengths (520 and 630 nm) differ significantly.

Superhard oxide coatings formed on titanium treated by high-frequency currents

We have studied the hardness and elastic modulus of rutile (TiO2) oxide coatings formed on the surface of commercial grade VT1-00 titanium treated by high-frequency current (HFC). The mechanism of formation of superhard oxide coatings with thicknesses within 2–3 μm and submicron-grained structure consisting of prismatic crystallites with dimensions of 200–400 nm. It is established that, at high temperatures (within 1000–1200°C) and short HFC treatment durations (30–300 s), the oxide coatings are characterized by hardnesses of about 61–78 GPa and elastic moduli within 330–680 GPa.

Induction heat treatment and technique of bioceramic coatings production on medical titanium alloys

Prospective composite bioceramic titania coatings were obtained on intraosseous implants fabricated from medical titanium alloy VT16 (Ti-2.5Al-5Mo-5V). Consistency changes of morphological characteristics, physico-mechanical properties and biocompatibility of experimental titanium implant coatings obtained by oxidation during induction heat treatment are defined. Technological recommendations for obtaining bioceramic coatings with extremely high strength on titanium items surface are given.

Fluorescent ZnCdS nanoparticles for nanothermometry of biological tissues

Internal temperature of biological tissues was measured in real-time mode under close-to-in-vivo conditions. Research technique is based on the comparison of the temperature inside the biological object and changes in the fluorescence spectra of temperature-sensitive fluorescent semiconductor ZnCdS nanoparticles introduced into muscle tissue. The temperature dependence of the ratio of maximum fluorescence intensities of the nanoparticles and the biological tissue was approximately linear.

Dynamic of gold nanoparticles labeling studied on the basis of OCT and backscattering spectra of tissues and phantoms

A new interference scheme of low-coherent interferometry was considered. This interference system does not use a special supporting beam. An object is lighted up by optical field directly from source of light. Back-scattered radiation is put to correlation analysis using Michelson scanning interferometer. Such unsupported interference system has a number of advantages, e.g. conducting experiments in vivo. A comparison of spatial sensitivity of OCT and HRT tomographs resolution was made during identification of local inhomogeneity in presence of nanoshells and nanorods in bio-phantoms and bio-tissues. Plasmon-resonant gold nanoparticles can be used as a new class of contrast agents in OCT diagnostics. The theoretical part of our study was to simulate the backscattering signal related to the process of electromagnetic wave propagation through a system of discrete scattering particles with consideration the effects of different scattering multiplicity. By using the computer Monte Carlo simulations, we calculated the spectra of collimated transmission, diffuse forward and back scattering for the systems of gold spherical particles and shells.