Concentration dependent structural ordering of poloxamine 908 on polystyrene nanoparticles and their modulatory role on complement consumption

Adsorption of poloxamine 908, a tetrafunctional polyethylene oxide (PEO)-polypropylene oxide ethylenediamine block copolymer, onto the surface of monodispersed polystyrene nanoparticles (232±0.33 nm) follows a bimodal pattern. Initially, the isotherm follows a Langmuir profile with a plateau observable over a very narrow equilibrium poloxamine concentration (0.0018–0.0031 mM). The isotherm then begins to rise again, reaching a final plateau at equilibrium poloxamine concentrations above 0.0089 mM. Similarly, the profile of the adsorbed layer thickness of poloxamine on the surface of nanoparticles is bimodal. The first plateau corresponds to a thickness of 4.6±0.07 nm, which occurs over the same range of poloxamine concentrations as in the initial plateau of the adsorption isotherm. The second plateau corresponds to a thickness of 9.53±0.32nm, observable at a minimum poloxamine concentration of 0.0067 mM. By using a calculated radius of gyration of a PEO chain in poloxamine as 3.1 nm, these observations reflect dynamic changes in the arrangement of surface projected PEO chains; a mushroom-like conformation at the first plateau region of the adsorption isotherm, followed by a transition into a brush-like conformation. These conformational changes are also reflected in rheological studies; the apparent viscosity of nanoparticles in which the PEO chains are in mushroom conformation is considerably higher than particles displaying the brush conformation. Further, atomic force microscopy studies (height profile and phase lag measurements) corroborated that the proposed poloxamine concentration dependent transition of surface associated PEO chains from mushroom to brush appearance is conserved when nanoparticles are dried under ambient conditions. Finally, we compared the influence of the surface PEO characteristics on complement consumption in human serum. Our results show complement-activating nature of all poloxamine-coated nanoparticles. However, complement consumption is reduced substantially with particles bearing a minimum of 11448 poloxamine molecules on their surface, thus demonstrating the importance of PEO surface density as well as brush conformation in suppressing complement consumption. This relationship between surface characteristics of poloxamine nanoparticles and their in vivo performance is discussed

Single-mode tellurite glass holey fiber with extremely large mode area for infrared nonlinear applications

We report the fabrication of a large mode area tellurite holey fiber from an extruded perform, with a mode area of 3000µm2. Robust single-mode guidance at 1.55µm was confirmed by both optical measurement and numerical simulation. The propagation loss was measured as 2.9dB/m at 1.55µm. A broad and flat supercontinuum from 0.9 to 2.5µm with 6mW output was obtained with a 9cm length of this fiber

Developing single-mode tellurite glass holey fiber for infrared nonlinear applications

We review our progress in developing single-mode tellurite glass holey fiber for infrared nonlinear applications. Tellurite glass preforms with complex holey structure were fabricated by using glass extrusion technique. The fabrication of single-mode tellurite holey fibers with the effective mode area ranging from 2.6-3000 µm2 and the effective nonlinearity gamma ranging from 0.23-280 W-1km-1 were demonstrated. By controlling the microstructured features in the holey cladding, the dispersion profile and the zero dispersion wavelength of this type of single-material optical fiber were tailored within a broad range. Broadband supercontinuum spectra from 0.9 to 2.5µm were generated from the fabricated fibers by using femtosecond laser. Attenuations due to the impurities, such as transition metal ions, rare-earth ions and hydroxyl groups, were also investigated in the bulk tellurite glass and fiber from visible to mid-infrared regimes

Developing single-mode tellurite glass holey fiber for infrared nonlinear applications

We review our progress on developing single-mode tellurite glass holey fiber for infrared nonlinear applications. Tellurite glass preforms with complex holey structure were fabricated by using glass extrusion technique. The fabrication of single mode tellurite holey fibers with the effective mode area ranging from 2.6-3000 µm2 and the effective nonlinearity gamma ranging from 0.23-280 W-1km-1 were demonstrated. By controlling the microstructured features in the holey cladding, the dispersion profile and the zero dispersion wavelength of this type of single material optical fiber were tailored within a broad range. Broadband 1.0-2.5 µm supercontinuum spectra were generated from the fabricated fibers by using femtosecond laser. Attenuation due to the impurities, such as transition metal ions, rare-earth ions and hydroxyl group, were also investigated in the bulk tellurite glass and fiber from visible to mid-infrared regimes