Som D. Tyagi

Optical properties of wounds: diabetic versus healthy tissue

Diffuse photon density wave (DPDW) methodology at Near Infrared frequencies has been used to calculate absorption and scattering from wounds of healthy and diabetic rats. The diffusion equation for semi-infinite media is being used for calculating the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain device. Differences observed during the course of healing in the two populations can be correlated to the delayed healing observed in diabetics. These results are encouraging and further work will focus on the implementation of this device to the clinical setting as a monitoring tool in chronic diabetic wounds.

A microprobe for the Cu(1) site in Y1Ba2Cu3O7−δ: emission Mössbauer studies using carrier-free cobalt-57

Abstract Carrier-free cobalt-57 serves as a good microprobe for Cu(1) sites in contrast to macroscopicallt substituted iron-57 used for absorption Mossbauer spectroscopy. In the oxygenated superconductor, the dominant species observed is the square planar Cu(1), while in the deoxygenated phase, the species representing Cu(1) site with two axial oxyanions is the dominant one. There is evidence of internal magnetic field at room temperature in the deoxygenated phase. The probe clearly shows the presence of two different phases, an oxygen rich and the other, the deficient one. The nucleus probes the delocalized s-electron density in the conduction band, and the magnitude of isomer shifts give indication of the degree of metallicity.

Changes in optical properties of tissue during acute wound healing in an animal model

Changes of optical properties of wound tissue in hairless rats were quantified by diffuse photon density wave methodology at near-infrared frequencies. The diffusion equation for semi-infinite media was used to calculate the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain device. There was an increase in the absorption and scattering coefficients and a decrease in blood saturation of the wounds compared with the nonwounded sites. The changes correlated with the healing stage of the wound. The data obtained were supported by immunohistochemical analysis of wound tissue. These results verified now by two independent animal studies could suggest a noninvasive method to detect the progress of wound healing.

Imaging biomarkers of inflammation in situ with functionalized quantum dots in the dextran sodium sulfate (DSS) model of mouse colitis

Abstract.Objective and design:Myeloperoxidase (MPO) and proinflammatory cytokines play an important role in the development of inflammation. These markers are generally measured using tedious ELISA procedures. In this study, a novel technique utilizing antibody conjugated quantum dot nanoparticles was developed to detect Myeloperoxidase, Interleukin-1α (IL-1α) and Tumor Necrosis Factor-α (TNF-α) in vivo in the dextran sodium sulfate (DSS) model of experimental colitis.Materials and methods:Colitis was induced in animals (n = 8 animals/group) by feeding 4% DSS solution ad libitum for seven to eight days. Quantum Dots (QDs) exhibiting fluorescence at various wavelengths were conjugated to MPO, IL-1α and TNF-α polyclonal antibodies and tested in vivo at various stages of colitis. Tissue sections obtained were imaged with confocal microscope. The image intensity obtained from the tissue specimen was correlated with clinical activity measured as Disease Activity Index (DAI).Results:Myeloperoxidase, IL-1α and TNF-α were visualized with quantum dots on various days of disease. The intensity of quantum dots increased with the increase in inflammation. The increase in intensity showed an excellent correlation with the DAI based on the clinical parameters.Conclusion:The study demonstrated that multiple biomarkers can be detected simultaneously and their quantitative expression correlated well with clinical disease severity. This novel technology should facilitate design of a novel optical platform for imaging various biomarkers of inflammation, early detection of acute and chronic disease markers and inflammation-mediated cancer markers. This detection may also facilitate determination of therapeutic success.

Near Infrared Diffuse Optical Tomography: Improving the Quality of Care in Chronic Wounds of Patients With Diabetes

A frequency domain diffuse optical tomography instrument operating in the Near Infrared region (680-830nm) has been designed and used to monitor healing in diabetic wounds in a rat animal model. Instrument design and calibration are described and preliminary data of the in vivo experiment are reported. Excellent discrimination capability between the control and the diabetic population is possible, while the time course of impaired healing in diabetic animals appears to have different optical coefficients from the normal healing in the control group.

Emission Mössbauer studies of the Y−Ba−Cu(57Co)−O system

During the usual thermal treatment of the superconducting YBa2Cu3O7 compound, cobalt and iron substitute predominantly at the Cu(1) site as shown by neutron and X-ray diffraction. EXAFS, and IR studies. A sequence of thermal treatments permits reversible cycling of cobalt-57 between the two copper sites. This allows us to micro-probe both the chain and the sheet site with varying degree of oxygen content.

A novel class of ferromagnetic materials

Abstract We have prepared a class of stable ferromagnetic materials with high Curie temperatures by thermal treatment of transition metal phthalocyanines, MnPc, FePc, CoPc or NiPc, for several hours at 500–700°C in inert ambient. Part of the phthalocyanine ring is pyrolyzed with corresponding loss in mass. Mossbauer studies of FePc and Co(57Co)Pc indicate that the MeN4 moiety and the aromatic character of the ring are retained, and that there is fairly strong interaction between the central atom and axially situated aromatic rings or nitrogens of neighboring coplanar rings. The axial interactions provide a pathway for ferromagnetism.

Bragg Grating Corrosion Sensor

Historically, corrosion has not been included in the calculation of the life expectancy of aircraft. It is well known how stress-corrosion cracking and corrosion fatigue can significantly reduce the life expectancy of structures. Therefore, it can be correctly assumed that some aircraft flying near their expected life might actually be flying well beyond their “safe life”. Furthermore, due to DoD present tight budget requirements, its is expected that some defense aircraft might not be retired at their original expected life but will be reconditioned to fly beyond that time. All of these considerations indicate that early detection, quantification and prevention of corrosion is of critical importance for military aircraft. This is particularly true for Navy aircraft which fly in the most corrosive environment of all services.

Microwave-absorption monitoring of aging and thermal-cycling effects in cuprate superconductors

Abstract Using direct and magnetically modulated microwave absorption, aging and thermal-cycling effects have been studied in single crystals and thin epitaxial films of Y 1 Ba 2 Cu 3 O 7 fabricated by laser ablation on LaAlO 3 substrates. The aging is most likely due to oxygen loss from the surface layers since the aging effects can be nearly completely reversed by isothermally annealing the samples in oxygen. The relevance of these results to the performance of microwave devices is discussed.

Bio-nano-optics for cellular investigations

We report results of our recent efforts to develop nano-tools to study proteins and their interactions in complex environments that exist on the cell membrane and inside the cells. Due to the spatial constraints imposed on the mobility of cell constituents, it is reasonable to expect that the nature and dynamics of the biomolecular interactions in a living cell would be substantially different from those routinely observed in dilute solutions. Nanotechnology has begun to provide tools with which to monitor processes that occur in membranes and intracellular regions. Nano-optics is a rich source of such emerging tools. Tapered optical fibers coated with metallic films can effectively confine excitation light to sub-wavelength linear dimensions and cubic nanometer excitation volumes. This leads not only to a resolution that exceeds the diffraction-limited values, but also to the elimination of the background signal. Thus, highly localized and specific regions of cellular function can be investigated. By immobilizing silver colloidal nanoparticles on such tapered fibers we have also fabricated surface enhanced Raman scattering (SERS) probes. Nanoprobes have been found to enable detection of fluorescent antibody molecules immobilized on a functionalized glass surface and polychromic quantum dots in picomolar solutions. In addition, we have successfully inserted nanoprobes with dimensions of 30-80 nm into both adherent insect and mammalian cells with maintenance of their viability. We summarize our development of optical nanoprobes with the motivation to detect cell-surface and intracellular proteins of the interleukin-5 system in native cellular environments, through quantum dot fluorescence and SERS.