TY - JOUR A1 - Bünger, H. A1 - Krüger, Ralph-Peter A1 - Pietschmann, S. A1 - Wüstneck, N. A1 - Kaufner, L. A1 - Tschiersch, R. A1 - Pison, U. T1 - Two hydrophobic protein fractions of ovine pulmonary surfactant: Isolation, characterisation and biophysical activity JF - Protein expression and purification N2 - Pulmonary surfactant contains two extremely hydrophobic proteins, SP-B and SP-C. We present a novel HPLC method for the preparation of these hydrophobic proteins. It is based on size-exclusion chromatography using the apolar stationary-phase butyl silica gel and isocratic elution with acidified chloroform/methanol. Samples for HPLC were prepared from sheep lung lavage fluid by centrifugation and extraction with chloroform/methanol. Amino acid analyses of the two protein fractions revealed sequences that are consistent with SP-B and SP-C, respectively. MALDI-TOF-MS analyses of the SP-B fraction showed one major peak of dimeric SP-B with m/z 17,361, and additional peaks of monomeric and oligomeric forms, which are predominantly even numbered. The SP-C fraction showed a peak at m/z 4200, consistent with the theoretical mass of the dipalmitoylated form of this protein. The biophysical activity of pure sheep SP-B and SP-C was evaluated by measuring the surface tension using axisymmetric drop shape analysis for captive bubbles. We found distinct surface pressure versus surface area isotherms of SP-B and SP-C indicating different biophysical activities for these surfactant proteins. The new preparative HPLC method is able to replace the established, time-consuming low-pressure liquid chromatography method for the isolation of SP-B and SP-C from lipids. KW - Surfactant proteins KW - SP-B KW - SP-C KW - Preparative HPLC KW - MALDI-TOF-MS KW - Surface pressure KW - Captive bubble PY - 2001 DO - https://doi.org/10.1006/prep.2001.1510 SN - 1046-5928 SN - 1096-0279 VL - 23 IS - 2 SP - 319 EP - 327 PB - Elsevier CY - Amsterdam AN - OPUS4-2174 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thünemann, Andreas A1 - Schütt, D. A1 - Kaufner, L. A1 - Pison, U. A1 - Möhwald, H. T1 - Maghemite Nanoparticles Protectively Coated with Poly(ethylene imine) and Poly(ethylene oxide)-block-poly(glutamic acid) JF - Langmuir N2 - Superparamagnetic iron oxide particles (SPIO) of maghemite were prepared in aqueous solution and subsequently stabilized with polymers in two layer-by-layer deposition steps. The first layer around the maghemite core is formed by poly(ethylene imine) (PEI), and the second one is formed by poly(ethylene oxide)-block-poly(glutamic acid) (PEO-PGA). The hydrodynamic diameter of the particles increases stepwise from Dh = 25 nm (parent) via 35 nm (PEI) to 46 nm (PEI plus PEO-PGA) due to stabilization. This is accompanied by a switching of their -potentials from moderately positive (+28 mV) to highly positive (+50 mV) and finally slightly negative (-3 mV). By contrast, the polydispersity indexes of the particles remain constant (ca. 0.15). Mössbauer spectroscopy revealed that the iron oxide, which forms the core of the particles, is only present as Fe(III) in the form of superparamagnetic maghemite nanocrystals. The magnetic domains and the maghemite crystallites were found to be identical with a size of 12.0 ± 0.5 nm. The coated maghemite nanoparticles were tested to be stable in water and in physiological salt solution for longer than 6 months. In contrast to novel methods for magnetic nanoparticle production, where organic solvents are necessary, the procedure proposed here can dispense with organic solvents. Magnetic resonance imaging (MRI) experiments on living rats indicate that the nanoparticles are useful as an MRI contrast agent. KW - Polymer KW - Polyelectrolyte KW - Mössbauer PY - 2006 DO - https://doi.org/10.1021/la052990d SN - 0743-7463 SN - 1520-5827 VL - 22 IS - 5 SP - 2351 EP - 2357 PB - American Chemical Society CY - Washington, DC AN - OPUS4-12119 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kaufner, L. A1 - Cartier, R. A1 - Wüstneck, R. A1 - Fichtner, I. A1 - Pietschmann, S. A1 - Bruhn, H. A1 - Schütt, Dagmar A1 - Thünemann, Andreas A1 - Pison, U. T1 - Poly(ethylene oxide)-block-poly(glutamic acid) coated maghemite nanoparticles: in vitro characterization and in vivo behaviour JF - Nanotechnology N2 - Positively charged superparamagnetic iron oxide (SPIO) particles of maghemite were prepared in aqueous solution and subsequently stabilized with poly(ethylene oxide)-block-poly(glutamic acid) (PEO–PGA) at a hydrodynamic diameter of 60 nm. Depending on the amount of PEO–PGA used, this is accompanied by a switching of their zeta potentials from positive to negative charge (-33 mV). As a prerequisite for in vivo testing, the PEO–PGA coated maghemite nanoparticles were evaluated to be colloidally stable in water and in physiological salt solution for longer than six months as well in various buffer systems under physiological pH and salt conditions (AFM, dynamic light scattering). We excluded toxic effects of the PEO–PGA coated maghemite nanoparticles. We demonstrated by in vivo MR-imaging and 111In measurements a biodistribution of the nanoparticles into the liver comparable to carboxydextran coated superparamagnetic iron oxide nanoparticles (Resovist®) as a reference nanoscaled MRI contrast medium. This was enforced by a detailed visualization of our nanoparticles by electron microscopy of liver tissue sections. Furthermore, our results indicate that 15% of the injected PEO–PGA coated maghemite nanoparticles circulate in the blood compartment for at least 60 min after i.v. application. KW - Nanotechnology KW - Nano Particle KW - Block-Copolymer PY - 2007 DO - https://doi.org/10.1088/0957-4484/18/11/115710 SN - 0957-4484 SN - 1361-6528 VL - 18 IS - 11 SP - 115710 (1 EP - 10) PB - IOP Publishing Ltd. CY - Bristol AN - OPUS4-16494 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -