Imaging of subcutaneous blood vessels and flow velocity profiles by optical coherence tomography

We have applied a compact low power rapid scanning Doppler Optical Coherence Tomography system to monitor multi-dimensional velocity profiles within the complex vessels and simultaneous real-time non-invasive imaging of skin tissues morphology in vivo, in the wavelength range of 1.3–1.5 nm. Optical clearing of skin tissues has been utilized to achieve depth of OCT images up to 1.7 mm. Current approach enables applying low-power (0.4–0.5 mW) and low-noise broadband near-infrared light sources and obtaining OCT images with down to 12 μm spatial resolution. Two-dimensional time-domain OCT images of complex flow velocity profiles in blood vessel phantom and in vivo subcutaneous human skin tissues are presented. The effect of optical clearing on in vivo images is demonstrated and discussed.     

Spectrophotometric system for measuring the characteristics of light scattered by biological tissues and humoral media

The structure, assembly, and physical capabilities of a spectrophotometric system intended for studying biotissues and humoral fluids are described. It can be used to investigate all the characteristics of scattered light at wavelengths of 400–1000 nm that are of interest for various problems in biomedical optics. Examples of these problems include noninvasive diagnostics of the structural and biophysical parameters of human skin tissue, analysis of the hemoglobin composition, sizes and degree of aggregation of erythrocytes, and evaluating the depth of penetration of light into biotissue. Pilot experiments on measuring the characteristics of scattered light are conducted in order to select an optimum operating mode for the system, estimate its errors, and develop ways of minimizing these errors.     

Nanoscale near-field infrared spectroscopic imaging of silica-shell/gold-core and pure silica nanoparticles

Spectroscopic near-field imaging of single silica-shell/Au-core and pure silica nanoparticles deposited on a silicon substrate is performed in the infrared wavelength range (λ = 9–11 μm) using scattering-type scanning near-field optical microscopy (s-SNOM). By tuning the wavelength of the incident light, we have acquired information on the spectral phonon–polariton resonant near-field interactions of the silica-shell/Au-core and pure silica nanoparticles with the probing tip. We made use of the enhanced near-field coupling between the high index Au-core and the probing tip to achieve spectral near-field contrast of the thin silica coating (thickness < 10 nm). Our results show that spectroscopic imaging of thin coating layers and complex core–shell nanoparticles can be directly performed by s-SNOM.     

Optical coherence tomography using broad-bandwidth XUV and soft X-ray radiation

We present a novel approach to extend optical coherence tomography (OCT) to the extreme ultraviolet (XUV) and soft X-ray (SXR) spectral range. With a simple setup based on Fourier-domain OCT and adapted for the application of XUV and SXR broadband radiation, cross-sectional images of semiconductors and organic samples becomes feasible with current synchrotron or laser-plasma sources. For this purpose, broadband XUV radiation is focused onto the sample surface, and the reflected spectrum is recorded by an XUV spectrometer. The proposed method has the particular advantage that the axial spatial resolution only depends on the spectral bandwidth. As a consequence, the theoretical resolution limit of XUV coherence tomography (XCT) is in the order of nanometers, e.g., 3 nm for wavelengths in the water window (280–530 eV). We proved the concept of XCT by calculating the reflectivity of one-dimensional silicon and boron carbide samples containing buried layers and found the expected properties with respect to resolution and penetration depth confirmed.     

Evaluation of skin optical clearing enhancement with Azone as a penetration enhancer

In order to find a non-invasive way to improve the efficacy of skin optical clearing with topically applied optical clearing agents (OCA), we evaluated the effect of Azone as a chemical penetration enhancer on optical clearing of intact skin in vitro. Fresh porcine skin with topical application of glycerol (G) mixed with various concentrations of water-soluble Azone (A_w) or propylene glycol (PG) mixed with oil-soluble Azone (A_o) was investigated. We measured changes in optical transmittance and diffuse reflectance of the skin under treatment with a near-infrared spectrophotometer. Light transmittance at 1276 nm increased by 37.3% and 41.1% at 60 min after the treatment in the cases with 40%PG5%A_o and 40%G5%A_w, respectively. Diffuse reflectance at 1066 nm decreased by 20.6% and 29.3% at 60 min after the treatment with 40%PG5%A_o and 40%G5%A_w, respectively. Forty percent glycerol or propylene glycol with the addition of Azone could achieve the same optical clearing effect as 80% glycerol. The results indicated that skin optical clearing with the topical application of glycerol and propylene glycol was markedly enhanced by both water-soluble and oil-soluble Azone. Skin penetration enhancing effect of Azone accounts probably for the skin clearing enhancement. In addition, Azone itself has shown optical clearing capability.     

Measurement of optical penetration depth and refractive index of human tissue

Experimental techniques for measurement of optical penetration depth and refractive index of humantissue are presented, respectively. Optical penetration depth can be obtained from the measurement ofthe relative fluence-depth distribution inside the target tissue. The depth of normal and carcinomatoushuman lung tissues irradiated with the wavelengths of 406.7, 632.8 and 674.4 nm in vitro are respectivelydetermined.In addition,a novel simple method based on total internal reflection for measuring therefractive index of biotissue in vivo is developed,and the refractive indices of skin from people of differentage, sex and skin color are measured.Their refractive indices are almost same and the average is 1.533.     

Enhanced activity of chaperonin GroEL in the presence of platinum nanoparticles

The chaperonin protein GroEL was mixed with varying concentrations of K₂PtCl₄ followed by a 20-fold concentration of sodium borohydride to afford GroEL–platinum nanoparticle complexes in a ratio of between 1:25 and 1:2,000. Typical colour change, from colourless or pale yellow to brown, occurred that was dependent on the amount of platinum present. These complexes were characterised by UV/Vis, inductively coupled plasma optical emission spectroscopy, Fourier transform infra red, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy. TEM analysis revealed that the size of nanoparticles increased as the molar ratio of platinum to GroEL increased with an average size diameter of 1.72–3.5 nm generated with GroEL–platinum molar ratios of 1:125–1:2,000. Fourier-transform infrared spectroscopy (FTIR) spectra showed no distinct changes in the structure of GroEL but confirmed that the nanoparticles were attached to the protein. The effect of platinum nanoparticles on the ATPase activity of GroEL showed an activity of 5.60 μmol min⁻¹ ml⁻¹ (87 % increase over a control) at the molar ratio of GroEL–platinum nanoparticles of 1:25.     

Manganese–gold nanoparticles as an MRI positive contrast agent in mesenchymal stem cell labeling

We report a straightforward approach to prepare multifunctional manganese–gold nanoparticles by attaching Mn(II) ions onto the surface of 20 nm citrate-capped gold nanoparticles. In vitro MRI measurements made in agarose gel phantoms exhibited high relaxivity (18.26 ± 1.04 mmol⁻¹ s⁻¹). Controlled incubation of the nanoparticles with mesenchymal stem cells (MSCs) was used to study cellular uptake of these particles and this process appeared to be controlled by the size of the nanoparticle aggregates in the extracellular solution. SEM images of live MSCs showed an increased concentration of particles near the cell membrane and a distribution of the size of particles within the cells. Survivability for MSCs in contact with Mn–Au NPs was greater than 97% over the 3-day period and up to the 1 mM Mn used in this study. The high relaxivity and low cell mortality are suggestive of an enhanced positive contrast agent for in vitro or in vivo applications.     

Optical and magneto-optical properties of Co–SiO<Subscript>x</Subscript> thin films

The optical and magneto-optical properties of hybrid Co–SiO_x systems are studied as a function of Co concentration. The structures were prepared by alternate depositions of SiO_x thin films and layers of 10-nm-diameter Co nanoparticles produced by an Ion Cluster Source. Both optical and magneto-optical constants of the system gradually increase with the amount of Co, though maintaining low optical absorption values in the visible range. The experimental results are well reproduced assuming that the nanoparticles have a cobalt core (7–8 nm in diameter) surrounded by a cobalt oxide shell (1–2 nm thick). The magneto-optical activity versus optical absorption figure of merit of this system is compared with other magneto-optical dielectric systems.     

Effect of storage conditions of skin samples on their optical characteristics

The optical characteristics of skin samples are experimentally studied ex vivo and in vitro at different storage conditions. The experiments are performed on a Cary-2415 spectrophotometer in the spectral range 400–700 nm. Based on the measured diffuse reflectance and total transmittance spectra, the spectra of the absorption and reduced scattering coefficients are calculated in terms of the inverse adding-doubling method. It is shown that the method of storage of samples mainly affects the reduced scattering coefficient of biotissue. Thus, upon storage of skin in an isotonic solution and in its absence, the reduced scattering coefficient increases ∼1.5 and ∼2 times, respectively, compared to the value of this parameter for the intact sample. The differences in the absorption spectra of ex vivo samples and samples stored under different conditions are the most noticeable in the absorption range of blood and are significant above 600 nm.     

Modeling laser irradiation conditions for mucosal tissues in antimicrobial photodynamic therapy

We use computer modeling to analzye empirically selected conditions for antimicrobial photodynamic therapy of mucosal tissues. We calculate the optical and thermal fields for experimental conditions for low-intensity (cold) laser irradiation used in treatment of lesions in mucosal tissues stained by methylene blue: λ = 670 nm, power density 150–300 mW/cm², doses 9–18 J/cm²; λ = 632.8 nm, 15 mW/cm², dose 4.5 J/cm². For numerical estimates, we used the optical characteristics of methylene blue and three layers of mucosal tissues at the laser radiation wavelengths, and also the thermal characteristics of the tissues. The experimental conditions were optimized using the ratio of the tissue penetration depth for the absorbed optical energy and the penetration depth of methylene blue into the lesion, while maintaining safe tissue heating temperatures.     

Compression as a method for increasing the informativity of optical coherence tomography of biotissues

The efficiency of the mechanical compression of biotissues for improving the differentiation between pathological changes in the structure of a biotissue observed by the method of optical coherence tomography (OCT) is investigated. The effect of the compression in the OCT-images of samples of the human rectum affected by inflammation and carcinoma is studied ex vivo. It is shown that the use of compression makes it possible to differentiate between these pathological changes. To interpret experimental data, images of an inflamed part of rectum are modeled by the Monte Carlo method for different degrees of compression. The results of modeling agree qualitatively with the experimental data.     

A wet chemical preparation of transparent conducting thin films of Al-doped ZnO nanoparticles

A wet chemical deposition method for preparing transparent conductive thin films on the base of Al-doped ZnO (AZO) nanoparticles has been demonstrated. AZO nanoparticles with a size of 7 nm have been synthesised by a simple precipitation method in refluxed conditions in ethanol using zinc acetate and Al-isopropylate. The presence of Al in ZnO was revealed by the EDX elemental analysis (1.8 at.%) and UV–Vis spectroscopy (a blue shift due to Burstein–Moss effect). The obtained colloid solution with the AZO nanoparticles was used for preparing by spin-coating thin films on glass substrates. The film demonstrated excellent homogeneity and transparency (T > 90%) in the visible spectrum after heating at 400 °C. Its resistivity turned to be excessively high (ρ = 2.6 Ω cm) that we ascribe to a poor charge percolation due to a high film porosity revealed by SEM observations. To improve the percolation via reducing the porosity, a sol–gel solution was deposited “layer-by-layer” in alternation with layers derived from the AZO colloid followed by heating. As it was shown by optical spectroscopy measurements, the density of thus prepared film was increased more than twice leading to a significant decrease in resistivity to 1.3 × 10⁻² Ω cm.     

Biosynthesis of silver nanoparticles using <Emphasis Type="Italic">Ocimum sanctum</Emphasis> (Tulsi) leaf extract and screening its antimicrobial activity

Development of green nanotechnology is generating interest of researchers toward ecofriendly biosynthesis of nanoparticles. In this study, biosynthesis of stable silver nanoparticles was done using Tulsi (Ocimum sanctum) leaf extract. These biosynthesized nanoparticles were characterized with the help of UV–vis spectrophotometer, Atomic Absorption Spectroscopy (AAS), Dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Transmission electron microscopy (TEM). Stability of bioreduced silver nanoparticles was analyzed using UV–vis absorption spectra, and their antimicrobial activity was screened against both gram-negative and gram-positive microorganisms. It was observed that O. sanctum leaf extract can reduce silver ions into silver nanoparticles within 8 min of reaction time. Thus, this method can be used for rapid and ecofriendly biosynthesis of stable silver nanoparticles of size range 4–30 nm possessing antimicrobial activity suggesting their possible application in medical industry.     

Efficient fabrication of transparent antimicrobial poly(vinyl alcohol) thin films

We have explored in situ synthesis of Ag nanoparticles in transparent PVA films in view of increasing areas of application of those films. The two-step procedure consists of ion incorporation in the matrix and subsequent thermal reduction. Smooth and transparent PVA films containing Ag nanoparticles of 5–20 nm were fabricated by this approach. The optical property of the films and the size of metal nanoparticles could be controlled by changing the reaction conditions. By increasing heating temperature, the absorbance and wavelength of surface plasmon resonance (SPR) of the composite film increased, and nanoparticles with larger particle sizes and broader size distributions were obtained. In the temperature range of 130–170 °C, the wavelength of SPR increased with increasing the AgNO₃ concentration. At 190 °C, however, the wavelenght of SPR blue-shifted initially when the AgNO₃ concentration increased from 10 to 80 mmol/L, and red-shifted thereafter. The composite films showed excellent antimicrobial performance toward bacteria such as Escherchia coli. Such hybrids afford very effective and environment-friendly antimicrobial surface coatings.     

Modelling of optical absorption of silver NP’s produced by UV radiation embedded in mesostructured silica films

Hexagonal mesostructured films containing silver ions were obtained by sol–gel method. Brij 58 was used to produce channels into the film, which house these ions. The films were exposure to UV radiation to produced silver metallic nanoparticles. The presence of the metallic nanoparticles was determined by infrared spectroscopy and optical absorption. Besides, these nanoparticles and core–shell structures of silver–silver oxide nanoparticles were identified by high-resolution transmission electronic microscopy. From these measurements, the obtained size range for silver nanoparticles was 6.1 nm. The absorption spectrum located at 440 nm was modelled and well fitted with the Gans theory considering refractive index higher than the one coming from host matrix. This index is explained because the silver oxide shell modifies the local surrounding medium of the metallic nanoparticles.     

Whole-body distribution of <Superscript>14</Superscript>C-labeled silica nanoparticles and submicron particles after intravenous injection into Mice

We analyzed the whole-body distribution of ¹⁴C–ADP-labeled silica nanoparticles (¹⁴C–ADP–SiO₂ nanoparticles) and submicron particles (¹⁴C–ADP–SiO₂ submicron particles) after intravenous injection into ICR mice. The ¹⁴C–ADP–SiO₂ nanoparticles and submicron particles were synthesized before the injection and the particle size was 19.6 and 130 nm, respectively. Similarly, the shape was spherical and the crystallinity was amorphous. After the synthesis, we injected mice with the ¹⁴C–ADP–SiO₂ nanoparticles or the ¹⁴C–ADP–SiO₂ submicron particles and dissected tissues after 1, 2, 4, 8 and 24 h. The radioactivity in the tissues was measured with a liquid scintillation counter. As a result, the retention percentage in bone, skin, lymph nodes, and the digestive mixture was at least twofold higher in the ¹⁴C–ADP–SiO₂ nanoparticles-exposed mice, whereas the retention percentage in the kidney was statistically higher in the ¹⁴C–ADP–SiO₂ submicron particles-exposed mice. Both types of ¹⁴C–ADP–SiO₂ particles mainly translocated to the muscle, bone, skin, and liver, but hardly translocated to the brain and olfactory bulb. Furthermore, the ¹⁴C–ADP–SiO₂ nanoparticles had a higher retention percentage (62.4 %) in the entire body at 24-h post-injection than did the ¹⁴C–ADP–SiO₂ submicron particles (50.7 %). Therefore, we suggested that the ¹⁴C–ADP–SiO₂ nanoparticles might be more likely than the ¹⁴C–ADP–SiO₂ submicron particles to be retained in the body, and consequently they might be gradually accumulated by chronic exposure.     

Silver nanoparticles embedded in amine-functionalized silicate sol–gel network assembly for sensing cysteine,adenosine and NADH

Silver nanoparticles embedded in amine-functionalized silicate sol–gel network were synthesized and used for sensing biomolecules such as cysteine, adenosine, and β-nicotinamide adenine dinucleotide (NADH). The sensing of these biomolecules by the assembly of silver nanoparticles was triggered by the optical response of the surface plasmon resonance (SPR) of the silver nanoparticles. The optical sensor exhibited the lowest detection limit (LOD) of 5, 20, and 5 μM for cysteine, adenosine, and NADH, respectively. The sensing of biomolecules in the micromolar range by using the amine-functionalized silicate sol–gel embedded silver nanoparticles was studied in the presence of interference molecules like uridine, glycine, guanine, and guanosine. Thus, the present approach might open up a new avenue for the development of silver nanoparticles-based optical sensor devices for biomolecules.     

Theranostic Iron@Gold Core–Shell Nanoparticles for Simultaneous Hyperthermia‐Chemotherapy upon Photo‐Stimulation

The challenges of nanoparticles, such as size‐dependent toxicity, nonbiocompatibility, or inability to undergo functionalization for drug conjugation, limit their biomedical application in more than one domain. Oval‐shaped iron@gold core–shell (oFe@Au) magnetic nanoparticles are engineered and their applications in magnetic resonance imaging (MRI), optical coherence tomography (OCT), and controlled drug release, are explored via photo stimulation‐generated hyperthermia. The oFe@Au nanoparticles have a size of 42.57 ± 5.99 nm and consist of 10.76 and 89.24 atomic % of Fe and Au, respectively. Upon photo‐stimulation for 10 and 15 minutes, the levels of cancer cell death induced by methotrexate‐conjugated oFe@Au nanoparticles are sixfold and fourfold higher, respectively, than oFe@Au nanoparticles alone. MRI and OCT confirm the application of these nanoparticles as a contrast agent. Finally, results of in vivo experiments reveal that the temperature is elevated by 13.2 °C, when oFe@Au nanoparticles are irradiated with a 167 mW cm^?2 808 nm laser, which results in a significant reduction in tumor volume and scab formation after 7 days, followed by complete disappearance after 14 days. The ability of these nanoparticles to generate heat upon photo‐stimulation also opens new doors for studying hyperthermia‐mediated controlled drug release for cancer therapy. Applications include biomedical engineering, cancer therapy, and theranostics fields.     

In situ electron beam irradiated rapid growth of bismuth nanoparticles in bismuth-based glass dielectrics at room temperature

In this study, in situ control growth of bismuth nanoparticles (Bi⁰ NPs) was demonstrated in bismuth-based glass dielectrics under an electron beam (EB) irradiation at room temperature. The effects of EB irradiation were investigated in situ using transmission electron microscopy (TEM), selected-area electron diffraction and high-resolution transmission electron microscopy. The EB irradiation for 2–8 min enhanced the construction of bismuth nanoparticles with a rhombohedral structure and diameter of 4–9 nm. The average particle size was found to increase with the irradiation time. Bismuth metal has a melting point of 271 °C and this low melting temperature makes easy the progress of energy induced structural changes during in situ TEM observations. This is a very useful technique in nano-patterning for integrated optics and other applications.