Photochromism and Electrochemistry of a Dithienylcyclopentene Electroactive Polymer

A bifunctional substituted dithienylcyclopentene photochromic switch bearing electropolymerisable methoxystyryl units, which enable immobilization of the photochromic unit on conducting substrates, is reported. The spectroscopic, electrochemical, and photochemical properties of a monomer in solution are compared with those of the polymer formed through oxidative electropolymerization. The electroactive polymer films prepared on gold, platinum, glassy carbon, and indium titanium oxide (ITO) electrodes were characterized by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The thickness of the films formed is found to be limited to several monolayer equivalents. The photochromic properties and stability of the polymer films have been investigated by UV/vis spectroscopy, electrochemistry, and XPS. Although the films are electrochemically and photochemically stable, their mechanical stability with respect to adhesion to the electrode was found to be sensitive to both the solvent and the electrode material employed, with more apolar solvents, glassy carbon, and ITO electrodes providing good adhesion of the polymer film. The polymer film is formed consistently as a thin film and can be switched both optically and electrochemically between the open and closed state of the photochromic dithienylethene moiety.

An : In vitro evaluation of fibrinogen and gelatin containing cryogels as dermal regeneration scaffolds

Macroporous cryogels containing mixtures of two key components of the dermal extracellular matrix, fibrinogen and collagen-derived gelatin, were evaluated for use as dermal tissue regeneration scaffolds. The infiltration of human dermal fibroblasts into these matrices was quantitatively assessed in vitro using a combination of cell culture and confocal laser scanning microscopy. The extent of cellular infiltration, as measured by the number of cells per distance travelled versus time, was found to be positively correlated with the fibrinogen concentration of the cryogel scaffolds; a known potentiator of cell migration and angiogenesis within regenerating tissue. An analysis of the proteins expressed by infiltrating fibroblasts revealed that the cells that had migrated into the interior portion of the scaffolds expressed predominantly F-actin along their cytoplasmic stress fibres, whereas those present on the periphery of the scaffolds expressed predominantly α-smooth muscle actin, indicative of a nonmotile, myofibroblast phenotype associated with wound contraction. In conclusion, the cryogels produced in this study were found to be biocompatible and, by alteration of the fibrinogen content, could be rendered more amenable to cellular infiltration

Micromechanical Properties of “Smart” Gels: Studies by Scanning Force and Scanning Electron Microscopy of PNIPAAm

Mechanical properties of PNIPAAm [poly-(N-isopropylacrylamide)] gel surfaces were studied using scanning force microscopy (SFM) in air or in water at various temperatures below and above the reversible phase transition at ~33 °C. SFM images of the gel surface were compared with those obtained in dry, swollen, and collapsed states using field emission scanning electron microscopy (FESEM). Images of SFM and FESEM of the dry gel surface revealed similar structural features. Force vs displacement curves were measured with both spherical (micrometer sized) and commercial probes. Indentation of the gel surface as a function of the probe load was evaluated to determine the local elastic modulus. For the swollen state at 10 °C, Young’s modulus was found to be more than 100 times lower than for the collapsed state at 35 °C.info:eu-repo/semantics/publishe