Cultivation of adherently growing cells in artificial environments is of utmost importance in medicine and biotechnology to accomplish in vitro drug screening or to investigate disease mechanisms. Precise cell manipulation, like localized control over adhesion, is required to expand cells, to establish cell models for novel therapies and to perform noninvasive cell experiments. To this end, we developed a method of gentle, local lift-off of mammalian cells using polymer surfaces, which are reversibly and repeatedly switchable between a cell-attractive and a cell-repellent state. This property was introduced through micropatterned thermoresponsive polymer coatings formed from colloidal microgels. Patterning was obtained through automated nanodispensing or microcontact printing, making use of unspecific electrostatic interactions between microgels and substrates. This process is much more robust against ambient conditions than covalent coupling, thus lending itself to up-scaling. As an example, wound healing assays were accomplished at 37 °C with highly increased precision in microfluidic environments.

When a nanomaterial enters a biological system, proteins adsorb onto the particle surface and alter the surface properties of nanoparticles, causing drastic changes in physicochemical properties such as hydrodynamic size, surface charge and aggregation state, thus giving a completely new and undefined physicochemical identity to the nanoparticles. In the present work, we study the impact of the protein identity (molecular weight and isoelectric point) and the environmental conditions (pH and ionic strength) on the final physicochemical properties of a model nanoparticle system, i.e. gold nanoparticles. Gold nanoparticles either form stable dispersions or agglomerate spontaneously when mixed with protein solutions, depending on the protein and the experimental conditions. Strikingly, the agglomerates redisperse to individually dispersed and colloidally stable nanoparticles, depending on the purification pH. The final protein coated nanoparticles exhibit specific stabilities and surface charges that depend on protein type and the conditions during its adsorption. By understanding the interactions of nanoparticles with proteins under controlled conditions, we can define the protein corona of the nanoparticles and thus their physicochemical properties in various media.

We present a new nanoporous multilayer system with a reversible pH-triggered swelling transition. Using the layer-by-layer approach, pH-responsive block copolymer micelles with a hydrophobic core, a weak polyanion shell and a strong polycation corona formed from an ABC triblock terpolymer are included within multilayer films. The approach of complexing the strong polycationic corona with a strong polyanion leads to the creation of novel double-end-tethered polyelectrolyte brush structures confined between the hydrophobic micellar cores and the interpolyelectrolyte complexes. The swelling degree, morphology as well as the mechanical properties of the coatings are reversibly tunable by the solution pH due to the ionization-induced swelling of the pH-sensitive polyelectrolyte-brush-like shell of the incorporated micelles resulting in large-scale volumetric changes of the film. Moreover, controlling the internal film architecture by the number of deposition steps allows tuning the properties of the porous multilayers such as the density of incorporated micelles, the porosity, and the equilibrium swelling degree to more than 1200%.

The adsorption of ionic amphiphilic diblock copolymers comprising a polycationic block, polybutadieneblock-poly(2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA); and its quaternized derivative (PB-b-PDMAEMAq) from aqueous media onto graphite-based surfaces was examined. Both diblock copolymers in aqueous solution form star-like micelles with a hydrophobic PB core and a cationic corona built up from either strong cationic PDMAEMAq or pH-sensitive PDMAEMA. AFM experiments show that PB-b-PDMAEMAq micelles interact slightly with a graphite surface providing films with a low surface coverage. PB-b-PDMAEMA micelles adsorbed onto a graphite surface at pH $ 7 result in a more homogeneous coverage of the graphite surface by the diblock copolymer. The adsorption of two enzymes, tyrosinase (Tyr) and choline oxidase (ChO) on the graphite surface premodified with these diblock copolymers was also monitored by AFM and by electrochemical measurements of the enzymatic activities of PB-b-PDMAEMA-Tyr and PB-b-PDMAEMA-ChO films. A pronounced increase in the enzymatic activity of tyrosinase was observed with the increasing concentration of PB-b-PDMAEMA micelles in solution used for their depositions. Also, a pronounced increase in the enzymatic activities of both tyrosinase and choline oxidase was observed with the increasing pH of the deposition of the micelles from 2 to 10. The enzymatic activity increases with the coverage of the graphite surface with the preadsorbed copolymer. Finally, the polymer-enzyme films were tested as biosensors for phenol (when tyrosinase was adsorbed) and choline (when choline oxidase was adsorbed) and their activity and stability were compared to already existing setups.

We investigate a morphological transition of surface-immobilized triblock terpolymer micelles: the splitting into well-defined clusters of satellite micelles upon pH changes. The multicompartment micelles are formed in aqueous solution of ABC triblock terpolymers consisting of a hydrophobic polybutadiene block, a weak polyanionic poly(methacrylic acid) block, and a weak polycationic poly(2-(dimethylamino)ethyl methacrylate) block. They are subsequently immobilized on silicon wafer surfaces by dip-coating. The splitting process is triggered by a pH change to strongly basic pH, which goes along with a charge reversal of the micelles. We find that the aggregation number of the submicelles is well-defined and that larger micelles have a tendency to split into a larger number of submicelles. Furthermore, there is a clear preference for clusters consisting of doublets and triplets of submicelles. The morphology of surface-immobilized clusters can be "quenched" by returning to the original pH. Thus, such well-defined micellar clusters can be stabilized and are available as colloidal building blocks for the formation of hierarchical surface structures. We discuss the underlying physicochemical principles of the splitting process considering changes in charge and total free energy of the micelles upon pH change.