Photoluminescence of Drying Droplets with Silicon Nanoparticles.

This study is dedicated to the formation of structures during drying of droplets of sols of silicon nanoparticles (SiNPs) in dimethylsulfoxide (DMSO) with a diameter of 1-5 mm on the horizontal glass and mica surfaces. Drying of such droplets with pinning (sticking) of the droplet contact line causes gradual gathering of the SiNPs on its edge with the formation of a thin ring. It has been found that the integral photoluminescence intensity IPL greatly varies during the drying process. At the initial stage, IPL monotonically decreases by several orders of magnitude and then abruptly increases several times at the final stage of ring formation. It has been shown that the rate of IPL decrease is maximal at a very early stage and depends both on the aggregative state (solid film SiNPs/sols of the SiNPs) and volume of the SiNPs sols. It is minimal for the solid film SiNPs and gradually increases as the volume of SiNPs sol in DMSO decreases (optical cell → big droplet → small droplet). The obtained experimental dependencies between the luminescence decrease rate and aggregative state and volumes of the SiNPs sol in DMSO are attributed to the combination of three mechanisms of luminescence quenching: photobleaching, quenching with atmospheric oxygen, and Förster resonance energy transfer quenching. The appearing of the luminescence leap at the final stage of ring formation is associated with the emergence of cracks in the ring.

Chitosan impregnation with biologically active tryaryl imidazoles in supercritical carbon dioxide.

The presented paper is focused on impregnation of chitosan and its derivatives with a biologically active triaryl imidazole model compound ((2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole) in the supercritical carbon dioxide medium. Since initial chitosan represents a polycation-exchange resin and does not swell in supercritical carbon dioxide, the impregnation was carried out in the presence of water (0.15-3.0 vol%). The maximum 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole concentration in a chitosan film was achieved at the ~5 × 10(-3) g/cm(3) water content in the reactor. We also used hydroxy carboxylic acid derivatives of chitosan and its copolymer with polylactide as matrices for introduction of hydrophobic 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole. We have shown that unmodified chitosan contains the greatest amount of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole, as compared with its hydrophobic derivatives. The kinetics of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole diffusion from a chitosan matrix was studied in acidified water with pH 1.6. We found that the complete release of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole into the aqueous phase from unmodified chitosan films occurred in 48 h, while its complete release from chitosan modified with hydroxy carboxylic acids occurred in 5 min or less.

Collagen structure deterioration in the skin of patients with pelvic organ prolapse determined by atomic force microscopy.

We used atomic force microscopy (AFM) to diagnose pathological changes in the extracellular matrix (ECM) of skin connective tissue in patients with pelvic organ prolapse (POP). POP is a common condition affecting women that considerably decreases the patients' quality of life. Deviations from normal morphology of the skin ECM from patients with POP occur including packing and arrangement of individual collagen fibers and arrangement of collagen fibrils. The nanoindentation study revealed significant deterioration of the mechanical properties of collagen fibril bundles in the skin of POP patients as compared with the skin of healthy subjects. Changes in the skin ECM appeared to correlate well with changes in the ECM of the pelvic ligament tissue associated with POP. AFM data on the ECM structure of normal and pathologically altered connective tissue were in agreement with results of the standard histological study on the same clinical specimens. Thus, AFM and related techniques may serve as independent or complementary diagnostic tools for tracking POP-related pathological changes of connective tissue.

Large-scale high-quality 2D silica crystals: dip-drawing formation and decoration with gold nanorods and nanospheres for SERS analysis.

High-quality colloidal crystals (CCs) are important for use in photonic research and as templates for large-scale plasmonic SERS substrates. We investigated how variations in temperature, colloid concentration, and dip-drawing parameters (rate, incubation time, etc) affect the structure of 2D CCs formed by highly monodisperse silica nanoparticles (SiNPs) synthesized in an l-arginine solution and regrown by a modified Stöber method. The best quality 2D CCs were obtained with aqueous 12 wt% colloids at a temperature of 25 °C, an incubation time of 1 min, and a drawing rate of 50 mm min(-1). Assembling of gold nanorods (GNRs) on 2D CCs resulted in the formation of ring-like chains with a preferential tail-to-tail orientation along the hexagonal boundaries. To the best of our knowledge, this is the first time that such nanostructures have been prepared. Owing to the preferential tail-to-tail packing of GNRs, 2D SiNP CC + GNR substrates demonstrated an analytical SERS enhancement of about 8000, which was 10 to 15 times higher than that for self-assembled GNRs on a silicon wafer. In addition, the analytical SERS enhancement was almost 60 times lower after replacing the nanorods in 2D SiNP CC + GNR substrates with 25 nm gold nanospheres.

Laser speckle probes of relaxation dynamics in soft porous media saturated by near-critical fluids.

Speckle correlation analysis was applied to study the relaxation dynamics in soft porous media saturated by near-critical carbon dioxide. The relaxation of soft matrix deformation was caused by a stepwise change in the fluid pressure. It was found that the deformation rate in the course of relaxation and the relaxation time strongly depend on the temperature of the system. The values of relaxation time reach their maximal values in the vicinity of the critical point of saturating fluid. The contributions of hydrodynamic relaxation of the fluid density and viscoelastic relaxation of the porous matrix to its creeping are analyzed.

Ex vivo laser thermoplasty of whole costal cartilages.

BACKGROUND AND OBJECTIVE: To examine the possibilities of laser thermoplasty of whole costal cartilages for correction the human congenital chest wall deformities. STUDY DESIGN/MATERIALS AND METHODS: Ex vivo the samples of porcine costal cartilages were heated with lasers of differing wavelengths, including a 0.97-µm diode laser, a 1.56-µm erbium-doped quartz fiber laser, and a 1.68-µm fiber Raman laser. The dynamics of the temperature fields and the degradation of collagen in the laser-affected regions of samples were determined by using, respectively, thermometry, trypsin treatment, and light microscopy. Ex vivo the whole mechanically deformed costal cartilages of pigs were treated by laser radiation with wavelength 1.68-µm. The changes of cartilage shape were recorded at certain intervals over a 24-hour period by photographing them in a fixed position with a digital camera. RESULTS: Treatment of costal cartilage samples from 5 to 11 mm in thickness by laser radiation with 0.97, 1.56, and 1.68 µm wavelengths showed that the 1.68-µm radiation could produce the necessary nonuniform bulk heating of the exposed sample. The altered shape of costal cartilage proved to remain stable after treatment when the laser irradiation settings used provided for the heating of a broad region within the tissue to temperatures about 80°C. CONCLUSION: This study demonstrates the possibilities of laser thermoplasty of whole costal cartilages for treatment of human congenital chest wall deformities. The development of novel approaches based on laser cartilage engineering techniques will enable to treat the human congenital chest wall deformities.

SERS substrates formed by gold nanorods deposited on colloidal silica films.

We describe a new approach to the fabrication of surface-enhanced Raman scattering (SERS) substrates using gold nanorod (GNR) nanopowders to prepare concentrated GNR sols, followed by their deposition on an opal-like photonic crystal (OPC) film formed on a silicon wafer. For comparative experiments, we also prepared GNR assemblies on plain silicon wafers. GNR-OPC substrates combine the increased specific surface, owing to the multilayer silicon nanosphere structure, and various spatial GNR configurations, including those with possible plasmonic hot spots. We demonstrate here the existence of the optimal OPC thickness and GNR deposition density for the maximal SERS effect. All other things being equal, the analytical integral SERS enhancement of the GNR-OPC substrates is higher than that of the thick, randomly oriented GNR assemblies on plain silicon wafers. Several ways to further optimize the strategy suggested are discussed.

3D fabrication of all-polymer conductive microstructures by two photon polymerization.

A technique to fabricate electrically conductive all-polymer 3D microstructures is reported. Superior conductivity, high spatial resolution and three-dimensionality are achieved by successive application of two-photon polymerization and in situ oxidative polymerization to a bi-component formulation, containing a photosensitive host matrix and an intrinsically conductive polymer precursor. By using polyethylene glycol diacrylate (PEG-DA) and 3,4-ethylenedioxythiophene (EDOT), the conductivity of 0.04 S/cm is reached, which is the highest value for the two-photon polymerized all-polymer microstructures to date. The measured electrical conductivity dependency on the EDOT concentration indicates percolation phenomenon and a three-dimensional nature of the conductive pathways. Tunable conductivity, biocompatibility, and environmental stability are the characteristics offered by PEG-DA/EDOT blends which can be employed in biomedicine, MEMS, microfluidics, and sensorics.

Biocompatibility and osteogenic potential of human fetal femur-derived cells on surface selective laser sintered scaffolds.

For optimal bone regeneration, scaffolds need to fit anatomically into the requisite bone defects and, ideally, augment cell growth and differentiation. In this study we evaluated novel computationally designed surface selective laser sintering (SSLS) scaffolds for their biocompatibility as templates, in vitro and in vivo, for human fetal femur-derived cell viability, growth and osteogenesis. Fetal femur-derived cells were successfully cultured on SSLS-poly(d,l)-lactic acid (SSLS-PLA) scaffolds expressing alkaline phosphatase activity after 7days. Cell proliferation, ingrowth, Alcian blue/Sirius red and type I collagen positive staining of matrix deposition were observed for fetal femur-derived cells cultured on SSLS-PLA scaffolds in vitro and in vivo. SSLS-PLA scaffolds and SSLS-PLA scaffolds seeded with fetal femur-derived cells implanted into a murine critical-sized femur segmental defect model aided the regeneration of the bone defect. SSLS techniques allow fabrication of biocompatible/biodegradable scaffolds, computationally designed to fit any defect, providing a template for cell osteogenesis in vitro and in vivo.

Attenuated total reflection Fourier transform infrared and polarization spectroscopy of in vivo human skin ablated, layer by layer, by erbium:YAG laser.

The results of an experimental study of the possibilities of monitoring erbium yttrium aluminum garnet laser-mediated ablation of human epidermis with the use of Fourier transform infrared (FTIR) spectroscopy and spectral polarization techniques are presented. The attenuated total reflection (ATR) method was used for FTIR spectroscopic measurements. Spectral polarization monitoring of the ablation was carried out by analyzing the spectra of the degree of residual linear polarization of a probe light diffusely reflected from the laser-treated region of skin. It was found that the analysis of FTIR spectra allows monitoring of the water and protein contents in the subsurface layers of the treated skin, while the degree of residual polarization measured at the wavelengths of maximal absorption of hemoglobin is sensitive to changes in the epidermis thickness and the blood content in the dermal layer (the degree of erythema).

Speckle-contrast monitoring of tissue thermal modification.

Measurements of the contrast value of time-averaged speckle-modulated images of cartilage tissue are used to study tissue thermal modification in the case of laser-light treatment. This modification is related to thermally induced internal stress relaxation in the matrix of the treated tissue. The specific feature of the evolution of time-averaged speckle contrast with a change in the current temperature of modified collagen tissue is the typical looplike form of the contrast-temperature dependencies associated with irreversible changes in tissue structure and correlated with changes in the tissue diffuse transmittance and the tissue internal stress mentioned by other researchers.