Biomedical subjects
Publications and source records attributed to R Mülhaupt.
Polar dyes can be solubilized in apolar media-molecular nanocapsules with hydrophilic interiors have been prepared (see schematic representation) using polyglycerols with narrow polydispersity and simple esterification with fatty acids. These unimolecular micelles offer attractive potential for a variety of applications ranging from controlled drug release to the design of microreactors and catalysts.
The attachment of mesogens as end groups to hyperbranched polyglycerol (degree of polymerization 22-45; see schematic representation, the rigid mesogens are shown as rods and the flexible alkyl chains as lines) leads to liquid crystalline polymers with narrow polydispersity, whose liquid crystalline behavior is induced by the mesogenic end groups only.
Coupling anticancer drugs to synthetic polymers is a promising approach of enhancing the antitumor efficacy and reducing the side-effects of these agents. Doxorubicin maleimide derivatives containing an amide or acid-sensitive hydrazone linker were therefore coupled to alpha-methoxy-poly(ethylene glycol)-thiopropionic acid amide (MW 20000 Da), alpha,omega-bis-thiopropionic acid amide poly(ethylene glycol) (MW 20000 Da) or alpha-tert-butoxy-poly(ethylene glycol)-thiopropionic acid amide (MW 70000 Da) and the resulting polyethylene glycol (PEG) conjugates isolated through size-exclusion chromatography. The polymer drug derivatives were designed as to release doxorubicin inside the tumor cell by acid-cleavage of the hydrazone bond after uptake of the conjugate by endocytosis. The acid-sensitive PEG conjugates containing the carboxylic hydrazone bonds exhibited in vitro activity against human BXF T24 bladder carcinoma and LXFL 529L lung cancer cells with IC70 values in the range 0.02-1.5 microm (cell culture assay: propidium iodide fluorescence or colony forming assay). In contrast, PEG doxorubicin conjugates containing an amide bond between the drug and the polymer showed no in vitro activity. Fluorescence microscopy studies in LXFL 529 lung cancer cells revealed that free doxorubicin accumulates in the cell nucleus whereas doxorubicin of the acid-sensitive PEG doxorubicin conjugates is primarily localized in the cytoplasm. Nevertheless, the acid-sensitive PEG doxorubicin conjugates retain their ability to bind to calf thymus DNA as shown by fluorescence and visible spectroscopy studies. Results regarding the effect of an acid-sensitive PEG conjugate of molecular weight 20000 in the chorioallantoic membrane (CAM) assay indicate that this conjugate is significantly less embryotoxic than free doxorubicin although antiangiogenic effects were not observed.
A new sample holder that allows combined microtomy for atomic force microscopy (AFM) and transmission electron microscopy (TEM) is described. The main feature of this sample holder is a small central part holding the sample. This central part fits into the head of an atomic force microscope. AFM measurements can be performed with a sample mounted in this central part of the sample holder. This makes the alignment of a microtomed bulk sample unnecessary, and offers the opportunity of an easy and fast combined sample preparation for AFM and TEM.
As a consequence of developing fully automated reactors for organic and organometallic synthesis and polymerizations combined with rapid on-line analysis, databases, and data mining, the analysis of polymers with respect to composition and properties has been speeded up. High-throughput evaluation of olefin copolymers requires fast measurements and high accuracy without tedious sample preparation such as pressing KBr pellets. This has been achieved by using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR spectroscopy) in conjunction with multivariate calibration in order to determine the composition of olefin copolymers such as ethene/propene, ethene/1-hexene and ethene/1-octene copolymers.