In recent years, both pharmaceutical companies and manufacturing industries have expressed heightened interest in the potential applications of magnetic nanoparticles for therapeutic and technological purposes. Specifically, pharmaceutical companies seek to employ magnetic nanoparticles as carriers to facilitate effective drug delivery, especially in areas of the brain. Manufacturing industries desire to use these nanoparticles as ferrofluids and in magnetic resonance imaging. However, data concerning the effects of magnetic nanoparticles on the nervous system is limited. This study tested the hypotheses that nanoparticles can (1) inhibit adherence of astrocytes to culture plates and (2) cause cytotoxicity or termination of growth, both end points representing surrogate markers of neurotoxicity. Using light microscopy, changes in plating patterns were determined by visual assessment. Cell counting 4 days after plating revealed a significant decrease in the number of viable astrocytes in nanoparticle treated groups (p < 0.0001). To determine the cytotoxic effects of nanoparticles, astrocytes were allowed to adhere to culture plates and grow to maturity for 3 weeks before treatment. Membrane integrity and mitochondrial function were measured using colorimetric analysis lactate dehydrogenase (LDH) and 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTS), respectively. Treatment with nanoparticles did not significantly alter astrocytic LDH release (p > 0.05) in the control group (100% +/- 1.56) vs the group receiving treatment (97.18% +/- 2.03). However, a significant increase in MTS activity (p < 0.05) between the control (100% +/- 3.65) and treated groups (112.8% +/- 3.23) was observed, suggesting astrocytic mitochondrial uncoupling by nanoparticles. These data suggest that nanoparticles impede the attachment of astrocytes to the substratum. However, once astrocytes attach to the substratum and grow to confluence, nanoparticles may cause mitochondrial stress.
Mixtures of a polyhedral oligomeric silsesquioxane, trisilanolisobutyl-POSS, and a polar silicone, poly(dimethyl-co-methylvinyl-co-methyl, 2-diphenyl phosphine oxide ethyl) siloxane (PDMS-PO), spread as Langmuir monolayers at the air/water interface are used to examine the surface phase behavior and aggregation of trisilanolisobutyl-POSS as a function of silicone composition. Analyses of the surface pressure-area per monomer (Pi-A) isotherms in terms of the collapse pressures and excess Gibbs free energies of mixing indicate the monolayers form slightly negative deviation mixtures. Direct observations of surface morphology with Brewster angle microscopy in the collapsed regime reveal that the governing factor for aggregation is the collapse Pi of the component with a stronger affinity for water. In trisilanolisobutyl-POSS/PDMS-PO blends, POSS aggregates as discrete domains and does not coalesce into larger aggregates or networklike structures for <80 wt % POSS, a feature that is vastly different from a previous study of POSS blended with regular poly(dimethylsiloxane).
This paper describes the use of free-standing electrically conductive ultra-low modulus materials that withstand elongations up to 1000% as sensors for the measurement of large strains. NanoSonic has developed novel, high performance, multifunctional polymers for use in self-assembly processing that result in durable free-standing conductive films -with both controlled nominal conductivity and Young's modulus. Such films exhibit a change in electrical conductivity as a function of tensile strain; whereby the magnitude of the change is controlled via chemical processing.
This paper discusses electrically conductive, shape changing, elastomeric nanocomposites capable of surviving repeated mechanical strains while remaining highly electrically conductive. Morphing nanocomposites were formed in-situ by chemically reacting monolayers of well defined, electrically conductive, nanostructured constituents with high performance shape memory copolymers. In this study, electrical conductivity was investigated as a function of volume fraction of nanoparticles and processing conditions. It was found that self-assembly processing results in percolation and surface resistivity of <1 Ohm/square with <0.01 volume % of metal nanoparticles. Waveguide measurements verified electrical stability of the thermoresponsive nanocomposites. The conclusion is that ultra-low mass density <0.99 g/cc skins formed via layer-by-layer processing exhibit electromagnetic integrity before, during and after shape change; when simulating disparate configurations that may be required on future morphing unmanned aerial vehicles.
We report recent improvements of Metal Rubber TM strain sensors formed by electrostatic self-assembly (ESA) processing. The sensors may be used to measure strains from approximately 1 microstrain to several hundred percent strain, over gauge lengths ranging from approximately 1 millimeter to several tens of centimeters.
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