Elasticity patterns induced by phase-separation in polymer blend films

Effect of Substrate Stiffness on Physicochemical Properties of Normal and Fibrotic Lung Fibroblasts

The presented research aims to verify whether physicochemical properties of lung fibroblasts, modified by substrate stiffness, can be used to discriminate between normal and fibrotic cells from idiopathic pulmonary fibrosis (IPF). The impact of polydimethylsiloxane (PDMS) substrate stiffness on the physicochemical properties of normal (LL24) and IPF-derived lung fibroblasts (LL97A) was examined in detail. The growth and elasticity of cells were assessed using fluorescence microscopy and atomic force microscopy working in force spectroscopy mode, respectively. The number of fibroblasts, as well as their shape and the arrangement, strongly depends on the mechanical properties of the substrate. Moreover, normal fibroblasts remain more rigid as compared to their fibrotic counterparts, which may indicate the impairments of IPF-derived fibroblasts induced by the fibrosis process. The chemical properties of normal and IPF-derived lung fibroblasts inspected using time-of-flight secondary ion mass spectrometry, and analyzed complexly with principal component analysis (PCA), show a significant difference in the distribution of cholesterol and phospholipids. Based on the observed distinctions between healthy and fibrotic cells, the mechanical properties of cells may serve as prospective diagnostic biomarkers enabling fast and reliable identification of idiopathic pulmonary fibrosis (IPF).

To study surface and sub-surface nanomechanical properties of electrospun polyacrylonitrile (PAN) nanofibers/polydimethylsiloxane (PDMS) composites

We investigate surface and sub-surface nanomechanical properties of nanocomposites based on a crosslinked polydimethylsiloxane (PDMS) elastomer and electrospun polyacrylonitrile (PAN) nanofibers. Fabrication of PDMS substrates with anisotropy with respect to surface elasticity and their characterization in terms of local nanomechanical properties are important for many areas of adhesion applications. PDMS nanocomposite substrates with variations in surface elasticity over large areas are prepared by controllably embedding electrospun PAN nanofibers (∼600 nm) in a PDMS matrix using the solution casting technique. Variations of local surface stiffness properties of prepared composites are measured using force spectroscopy and force mapping modes of atomic force microscopy and compared with their macroscopic (bulk) mechanical properties. Since the surface of the prepared nanocomposite is elastically non-homogeneous, our studies are mainly focused on the investigation of the hysteresis (plasticity index) between loading and unloading curves which is a measure of energy dissipation in AFM indentation experiments. The distribution of the local plasticity index in the PAN/PDMS composites is related to the specific organization of electrospun nanofibers at the surface and sub-surface layers of the PDMS matrix. We observed that embedding 0.1-1% PAN nanofibers induces anti-plasticization effects for lower (0.1%) and higher (1%) concentrations of PAN nanofibers which represent the formation of interpenetrating networks and mat-like blended structures of PAN nanofibers within the PDMS matrix.