Nicht-wässrige Emulsionen zur Erzeugung neuer Nanopartikel

In der eingereichten Arbeit wurde die Nutzung von nicht-wässrigen Emulsionen, bestehend aus zwei organischen, aprotischen Lösungsmitteln, zur Erzeugung verschiedener polymerer Nanopartikel beschrieben. Diese Zweiphasenmischungen und die Verwendung maßgeschneiderter Emulgatoren bestehend aus Poly(isopren-block-methylmethacrylat) ermöglichten den Zugang zu einer Vielzahl an Reaktionen und Prozessen, welche in wässrigen Emulsionen bisher nicht oder nur schwer möglich waren. Die Generierung von Partikeln auf Basis katalytischer Polymerisationen erfolgte unter Verwendung der Ringöffnenden Metathese-Polymerisation (ROMP), der Acyclischen Dien-Metathese-Polymerisation (ADMET), der Cyclopolymerisation von α,ω-Diinen und der Ni-katalysierten Polymerisation von Isocyaniden. Mittels ROMP konnten stabile Dispersionen erzeugt werden, welche Partikel mit verschiedensten Molekulargewichten, Größen und Morphologien enthielten. Diese Eigenschaften konnten durch die Wahl des Monomers, die Katalysatorkonzentration oder den Emulgatortyp beeinflusst werden. Des Weiteren wurden Partikel mit komplexen Morphologien wie Kern-Schale-Strukturen synthetisiert. Dazu erfolgte die Generierung von Partikeln aus Poly(urethan) oder Poly(norbornenderivaten), welche in situ und ohne intermediäre Aufarbeitung mit einer Schale aus Poly(methacrylat) versehen wurden. Der Nachweis dieser Strukturen gelang mittels verschiedener Schwermetall-Markierungsverfahren in der Transmissionselektronenmikroskopie. Schlussendlich erfolgte die Herstellung von hochvernetzten und molekular geprägten Poly(acrylsäure)-Partikeln. Hierbei wurden unterschiedliche pharmakologische Wirkstoffe und Farbstoffe in die Partikel eingebracht, um deren Migrationsverhalten und Wiederanbindung an die Partikel zu untersuchen. Weiterhin wurden die Partikel erfolgreich in Zellaufnahmeexperimenten eingesetzt.

Decay of imprinted surface waves in polymers

CONCLUSIONS The focus of this work was the investigation ofanomalies in Tg and dynamics at polymer surfaces. Thethermally induced decay of hot-embossed polymer gratings isstudied using laser-diffraction and atomic force microscopy(AFM). Monodisperse PMMA and PS are selected in the Mwranges of 4.2 to 65.0 kg/mol and 3.47 to 65.0 kg/mol,respectively. Two different modes of measurement were used:the one mode uses temperature ramps to obtain an estimate ofthe near-surface glass temperature, Tdec,0; the other modeinvestigates the dynamics at a constant temperature aboveTg. The temperature-ramp experiments reveal Tdec,0 valuesvery close to the Tg,bulk values, as determined bydifferential scanning calorimetry (DSC). The PMMA of65.0 kg/mol shows a decreased value of Tg, while the PS samples of 3.47 and 10.3 kg/mol (Mwmolecular weight for PMMA. PS is fragile for all Mw asexpected for linear polymers. Non-Arrhenius behavior allowsone to fit the shift factors to the William-Landel-Ferry(WLF) equation. The WLF parameters for the varying molecular weights ofPMMA and PS were extracted and compared to the values frombulk rheology measurements. Assuming cg1=16+/-2 at Tg, assuggested by Angell, the glass temperature was determinedfrom the dynamic decay experiments. Within the experimentalerrors, the values for Tg,surf(c1=16) and T_g,bulk(c1=16)tend to be smaller than Tdec,0 and Tg,bulk fromtemperature-ramp and DSC measurements, but confirm thecourse of the values with increasing Mw. The comparison of the fragilities (temperaturedependence of the polymer properties at Tg) near the surfaceand in the bulk shows a higher fragility for PS near thesurface, a lower one for PMMA with molecular weights of 4.2and 65.0 kg/mol. The different surface behavior of PS istraced back to a lower degree of cooperation and a largerfree volume fraction.

New biosensor applications of surface plasmon and hydrogel optical waveguide spectroscopy

Rapid and sensitive detection of chemical and biological analytes becomes increasingly important in areas such as medical diagnostics, food control and environmental monitoring. Optical biosensors based on surface plasmon resonance (SPR) and optical waveguide spectroscopy have been extensively pushed forward in these fields. In this study, we combine SPR, surface plasmon-enhanced fluorescence spectroscopy (SPFS) and optical waveguide spectroscopy with hydrogel thin film for highly sensitive detection of molecular analytes.rnrnA novel biosensor based on SPFS which was advanced through the excitation of long range surface plasmons (LRSPs) is reported in this study. LRSPs are special surface plasmon waves propagating along thin metal films with orders of magnitude higher electromagnetic field intensity and lower damping than conventional SPs. Therefore, their excitation on the sensor surface provides further increased fluorescence signal. An inhibition immunoassay based on LRSP-enhanced fluorescence spectroscopy (LRSP-FS) was developed for the detection of aflatoxin M1 (AFM1) in milk. The biosensor allowed for the detection of AFM1 in milk at concentrations as low as 0.6 pg mL-1, which is about two orders of magnitude lower than the maximum AFM1 residue level in milk stipulated by the European Commission legislation.rnrnIn addition, LRSPs probe the medium adjacent to the metallic surface with more extended evanescent field than regular SPs. Therefore, three-dimensional binding matrices with up to micrometer thickness have been proposed for the immobilization of biomolecular recognition elements with large surface density that allows to exploit the whole evanescent field of LRSP. A photocrosslinkable carboxymethyl dextran (PCDM) hydrogel thin film is used as a binding matrix, and it is applied for the detection of free prostate specific antigen (f-PSA) based on the LRSP-FS and sandwich immunoassay. We show that this approach allows for the detection of f-PSA at low femto-molar range, which is approximately four orders of magnitude lower than that for direct detection of f-PSA based on the monitoring of binding-induced refractive index changes.rnrnHowever, a three dimensional hydrogel binding matrix with micrometer thickness can also serve as an optical waveguide. Based on the measurement of binding-induced refractive index changes, a hydrogel optical waveguide spectroscopy (HOWS) is reported for a label-free biosensor. This biosensor is implemented by using a SPR optical setup in which a carboxylated poly(N-isoproprylacrylamide) (PNIPAAm) hydrogel film is attached on a metallic surface and modified by protein catcher molecules. Compared to regular SPR biosensor with thiol self-assembled monolayer (SAM), HOWS provides an order of magnitude improved resolution in the refractive index measurements and enlarged binding capacity owing to its low damping and large swelling ratio, respectively. A model immunoassay experiment revealed that HOWS allowed detection of IgG molecules with a 10 pM limit of detection (LOD) that was five-fold lower than that achieved for SPR with thiol SAM. For the high capacity hydrogel matrix, the affinity binding was mass transport limited.rnrnThe mass transport of target molecules to the sensor surface can play as critical a role as the chemical reaction itself. In order to overcome the diffusion-limited mass transfer, magnetic iron oxide nanoparticles were employed. The magnetic nanoparticles (MNPs) can serve both as labels providing enhancement of the refractive index changes, and “vehicles” for rapidly delivering the analytes from sample solution to an SPR sensor surface with a gradient magnetic field. A model sandwich assay for the detection of β human chorionic gonadotropin (βhCG) has been utilized on a gold sensor surface with metallic diffraction grating structure supporting the excitation of SPs. Various detection formats including a) direct detection, b) sandwich assay, c) MNPs immunoassay without and d) with applied magnetic field were compared. The results show that the highly-sensitive MNPs immunoassay improves the LOD on the detection of βhCG by a factor of 5 orders of magnitude with respect to the direct detection.rn