Anti-allergic effect of low molecular weight β-glucan prepared by λ-irradiation

This study evaluated the anti-allergic effect of low molecular weight β-glucan (25 kDa) degraded by λ-irradiation. Allergy was induced in mouse models administrated with λ-irradiated low molecular weight and non-irradiated high molecular weight β-glucan, respectively, for 7 days. However, only the mice treated with low molecular weight β-glucan had a significantly decreased the total serum IgE and ovalbumin specific-IgE levels, and significantly increased Th 1 cytokine expression compared to only allergy induced mice. The allergic responses could be reduced by low molecular weight β-glucan treated λ-irradiation through the increased expression of Th 1 response and decreased expression of total IgE and antigen specific IgE.     

Fluorescence quenching by colloidal heavy metals nanoparticles: implications for correlative fluorescence and electron microscopy studies

Labels for correlative immunolabeling in light (LM) and electron microscopy (EM) employing colloidal metal nanoparticles (gold or palladium) and fluorescent dyes (Alexa Fluor, AF) were investigated. The fluorescence signals from direct conjugates (cAu-IgG-AF) and from an indirect label system (cAu-IgG-anti IgG-AF) were studied using scanning spectrofluorometry and fluorescence light microscopy. Direct conjugation of protein--AF, IgG-AF or FGN-AF to 18 and 5 nm colloidal gold (cAu18 and cAu5) or 12 nm colloidal palladium particles (cPd12) resulted in nearly completely quenched fluorescence signals (>99 %) at excitation wavelengths of 488, 546 and 594 nm. In contrast, indirect conjugation, when colloidal metal particles and AF were conjugated to primary or secondary antibody, respectively (cAu-IgG-antiIgG-AF), sufficient fluorescence signal was detected. Commercially available conjugates, consisting of IgG-AF-cAu5 and IgG-AF-cAu10, were also tested and proved to be a mixture of IgG-AF (unbound to cAu) and cAu-IgG-AF.     

Study of tablet-coating parameters for a pan coater through video imaging and Monte Carlo simulation

The movement of tablets in a pan coater and the exposure of different surfaces of tablets for deposition of coatings by spray-coating have been studied by video imaging and Monte Carlo simulation techniques. A representative variety of tablets of different shapes and sizes were used at different pan loads and at various pan speeds. A single “tracer” tablet was used to track the motion of tablets and coating variables such as circulation time, surface time, projected surface area and surface velocity of a tablet were determined from the video imaging experiments. The coating uniformity is described in terms of the coating variation from tablet to tablet CV(tt) and a new parameter CV(st) the coating variation on a single tablet. The effect of shape of tablets on coating uniformity was analyzed by introducing a “sphericity” of tablet (φ_s) into the CV models. The methodology, new models and the analysis developed here incorporating the additional parameters will help users to optimize the coating process in pan-coating operations.     

Collision cross section of fast beam by neutral gas target

Effective deexcitation cross sections of fast beams of Na, Ne, and Li+ in the excited P state at energies of -160 keV with a N2 gas target are reported. These cross sections are obtained from analysis of the dependence of the effective lifetime on the gas pressure. Results for neon indicate small variations of deexcitation cross section for the different 3p fine structure levels.     

Flexible Transient Optical Waveguides and Surface‐Wave Biosensors Constructed from Monocrystalline Silicon

Optical technologies offer important capabilities in both biological research and clinical care. Recent interest is in implantable devices that provide intimate optical coupling to biological tissues for a finite time period and then undergo full bioresorption into benign products, thereby serving as temporary implants for diagnosis and/or therapy. The results presented here establish a silicon‐based, bioresorbable photonic platform that relies on thin filaments of monocrystalline silicon encapsulated by polymers as flexible, transient optical waveguides for accurate light delivery and sensing at targeted sites in biological systems. Comprehensive studies of the mechanical and optical properties associated with bending and unfurling the waveguides from wafer‐scale sources of materials establish general guidelines in fabrication and design. Monitoring biochemical species such as glucose and tracking physiological parameters such as oxygen saturation using near‐infrared spectroscopic methods demonstrate modes of utility in biomedicine. These concepts provide versatile capabilities in biomedical diagnosis, therapy, deep‐tissue imaging, and surgery, and suggest a broad range of opportunities for silicon photonics in bioresorbable technologies.     

Cure kinetics and thermomechanical properties of thermally stable photopolymerized dimethacrylates

A range of dimethacrylates with varying backbone flexibility were partially photocured to various conversions using p‐xylylene bis‐(N,N‐diethyldithiocarbamate) as a photoiniferter and their glass transition region investigated by dynamic mechanical thermal analysis. For isothermally cured samples, the final degree of conversion was found to increase as the length of the spacer group in the monomer was increased or as the crosslink density in the resin was lowered due to the reduced glass transition temperature which allowed greater mobility and, hence, higher cure. Increasing the curing temperature also resulted in a higher degree of conversion as the network was able to polymerize further before vitrification occurred. For the partially photocured samples, the glass transition temperature was raised as the degree of conversion was increased. Most of the measures of the breadth of the glass transition were found to increase with increased conversion for dimethacrylates with short or stiff backbones (TETDMA and bisGMA) while the transition breadth was independent of conversion for either a more flexible dimethacrylate (NEGDMA) or a dimethacrylate network with a lower crosslink density (50 wt % bisGMA/50 wt % PGEMA). This conclusion was generally confirmed by analysis of the viscoelastic parameters in the frequency domain. It is not clear whether these behaviors resulted from differences in the range of molecular motions available in tight networks or if they were due to spatially heterogeneous regions in the network. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3753–3766, 2003