RESUMO
The possibility of using a single electroactive and luminescent molecule both as a redox mediator and as a fluorophore in an experiment combining in situ Scanning Electrochemical Microscopy (SECM) and epifluorescence microscopy was validated. The usual working modes of SECM, namely positive and negative feedback as well as generation-collection, were used and the fluorescence images, intensity and spectra were recorded for each configuration. The tip potential, tip-substrate distance and, in the case of a conducting substrate, the substrate potential are the parameters that are likely to control the fluorescence. It is shown that the tip can be used to switch on and off the luminescence and that the modulation amplitude maximum is sensitive to the nature of the substrate. Approach curves based on this fluorescence modulation amplitude can be obtained showing a higher sensitivity than the classical electrochemical ones.
RESUMO
Dynamic guidance of living cells is achieved by fine-tuning and spatiotemporal modulation on artificial polymer layers enabling reversible peptide display. Adjustment of surface composition and interactions is obtained by coadsorption of mixed poly(lysine) derivatives, grafted with either repellent PEG, RGD adhesion peptides, or T-responsive poly(N-isopropylacrylamide) strands. Deposition of mixed adlayers provides a straightforward mean to optimize complex substrates, which is here implemented to achieve (1) thermal control of ligand accessibility and (2) adjustment of relative adhesiveness between adjacent micropatterns, while preserving cell attachment during thermal cycles. The reversible polarization of HeLa cells along orthogonal stripes mimics guidance along natural matrices.
