On-Demand Cell Sheet Release with Low Density Peptide-Functionalized Non-LCST Polymer Brushes.

Cell sheet harvesting offers a great potential for the development of new therapies for regenerative medicine. For cells to adhere onto surfaces, proliferate, and to be released on demand, thermoresponsive polymeric coatings are generally considered to be required. Herein, an alternative approach for the cell sheet harvesting and rapid release on demand is reported, circumventing the use of thermoresponsive materials. This approach is based on the end-group biofunctionalization of non-thermoresponsive and antifouling poly(2-hydroxyethyl methacrylate) (p(HEMA)) brushes with cell-adhesive peptide motifs. While the nonfunctionalized p(HEMA) surfaces are cell-repellant, ligation of cell-signaling ligand enables extensive attachment and proliferation of NIH 3T3 fibroblasts until the formation of a confluent cell layer. Remarkably, the formed cell sheets can be released from the surfaces by gentle rinsing with cell-culture medium. The release of the cells is found to be facilitated by low surface density of cell-adhesive peptides, as confirmed by X-ray photoelectron spectroscopy. Additionally, the developed system affords possibility for repeated cell seeding, proliferation, and release on previously used substrates without any additional pretreatment steps. This new approach represents an alternative to thermally triggered cell-sheet harvesting platforms, offering possibility of capture and proliferation of various rare cell lines via appropriate selection of the cell-adhesive ligand.

Potentiometric Performance of Ion-Selective Electrodes Based on Polyaniline and Chelating Agents: Detection of Fe2+ or Fe3+ Ions.

We constructed a sensor for the determination of Fe2+ and/or Fe3+ ions that consists of a polyaniline layer as an ion-to-electron transducer; on top of it, chelating molecules are deposited (which can selectively chelate specific ions) and protected with a non-biofouling poly(2-methyl-2-oxazoline)s layer. We have shown that our potentiometric sensing layers show a rapid response to the presence of Fe2+ or Fe3+ ions, do not experience interference with other ions (such as Cu2+), and work in a biological environment in the presence of bovine serum albumin (as a model serum protein). The sensing layers detect iron ions in the concentration range from 5 nM to 50 µM.

Conformation in Ultrathin Polymer Brush Coatings Resolved by Infrared Nanoscopy.

Polymer brush coatings are effective in preventing blood coagulation or bacterial attachment, but their chain conformation, while vital for this effect, was never characterized in high spatial resolution. Here, we report mid-infrared spectroscopic nanoscopy studies of few-nanometer-thin poly(ethylene oxide) (PEO) films which reveal marked spectral variations along the surface at a length scale smaller than 100 nm and originating only from the physical conformation of the chains. The conformation and average orientation of the polymer chains in the layer is extracted from the spectra with the aid of theoretic modeling, confirming the spontaneous formation of a crystalline phase. This result suggests spectroscopic nanoscopy as a powerful new tool to characterize polymer brush coatings.