@article{UhligWischerhoffLutzetal.2010, author = {Uhlig, Katja and Wischerhoff, Erik and Lutz, Jean-Francois and Laschewsky, Andr{\´e} and J{\"a}ger, Magnus S. and Lankenau, Andreas and Duschl, Claus}, title = {Monitoring cell detachment on PEG-based thermoresponsive surfaces using TIRF microscopy}, issn = {1744-683X}, doi = {10.1039/C0sm00010h}, year = {2010}, abstract = {Recently, we introduced a thermoresponsive copolymer that consists of oligo(ethylene glycol) methacrylate (OEGMA) and 2-(2- methoxyethoxy) ethyl methacrylate (MEO(2)MA). The polymer exhibited an LCST at 35 degrees C in PBS buffer and was anchored onto gold substrates using disulfide polymerisation initiators. It allows the noninvasive detachment of adherent cells from their substrate. As the mechanisms that determine the interaction of cells with such polymers are not well understood, we employed Total Internal Reflection Fluorescence (TIRF) microscopy in order to monitor the detachment process of cells of two different types. We identified contact area and average cell-substrate distance as crucial parameters for the evaluation of the detachment process. The sensitivity of TIRF microscopy allowed us to correlate the specific adhesion pattern of MCF-7 breast cancer cells with the morphology of cell deposits that may serve as fingerprints for a nondestructive characterisation of live cells.}, language = {en} } @article{UhligMadaboosiSchmidtetal.2012, author = {Uhlig, Katja and Madaboosi, Narayanan and Schmidt, Stephan and J{\"a}ger, Magnus S. and Rose, J{\"u}rgen and Duschl, Claus and Volodkin, Dmitry V.}, title = {3d localization and diffusion of proteins in polyelectrolyte multilayers}, series = {Soft matter}, volume = {8}, journal = {Soft matter}, number = {47}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c2sm26500a}, pages = {11786 -- 11789}, year = {2012}, abstract = {The interaction of diverse biomaterials with surfaces is more crucial than ever for biomedical applications to ensure efficiency and reproducibility. Very interesting surface materials are micrometer-thick polyelectrolyte multilayers. Not only their surface but also the bulk can be loaded with biomaterials like proteins or DNA for various purposes. Therefore, we established a method to analyze the lateral and vertical distribution of fluorescently labelled proteins of various size and charge in polyelectrolyte films composed of poly(L-lysine) and hyaluronic acid by confocal laser scanning microscopy. This approach enables us to measure the diffusion coefficients of the proteins via fluorescence recovery after photobleaching as a function of their vertical position in the film and facilitates the understanding of molecular interactions in the film with a high resolution in both space and time. As a result, we confirm that protein loading in the film is driven by electrostatic interactions - uncharged dextran molecules of 10 and 500 kDa do not diffuse into the film. Proteins of different sizes (3-11 nm) can diffuse relatively fast (D = 2-4 mm(2) s(-1)) independent of their net charge, indicating complex interpolymer interactions. This approach is a new powerful experimental tool to design the polyelectrolyte multilayers for bio-applications by finding a relationship between intermolecular interactions and mobility and availability of biomolecules to biological samples (e.g. cells) or detection units (e.g. biosensors).}, language = {en} }