The introduction of electrostatic layer-by-layer (LbL) self-assembly has shown broad biomedical applications in thin film coating, micropatterning, nanobioreactors, artificial cells, and drug delivery systems. Multiple assembly polyelectrolytes and proteins are based on electrostatic interaction between oppositely charged layers. The film architecture is precisely designed and can be controlled to 1-nm precision with a range from 5 to 1000 nm. Thin films can be deposited on any surface including many widely used biomaterials. Microencapsulation of micro/nanotemplates with multilayers enabled cell surface modification, controlled drug release, hollow shell formation, and nanobioreactors. Both in vitro and in vivo studies indicate potential applications in biology, pharmaceutics, medicine, and other biomedical areas.

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Platelets were coated with 78-nm silica nanoparticles, 45-nm fluorescent nanospheres, or bovine immunoglobulin G (IgG) through layer-by-layer assembly by alternate adsorption with oppositely charged linear polyions. Sequential deposition on platelet surfaces of cationic poly(dimethyldiallylammonium chloride) and anionic poly(styrene sulfonate) was followed by adsorption of nanoparticles or immunoglobulins. Nano-organized shells of platelets were demonstrated by transmission electron microscopy and fluorescence microscope images. Bovine IgG was assembled on platelets, as verified with anti-bovine IgG-FITC labeling. Localized targeting of anti-IgG shelled platelets was also demonstrated. An ability to coat blood cells with nano-organized shells can have applications in cardiovascular research and targeted drug delivery.

Viscous shearing is examined as a mechanism by which turbulent flows can cause cellular damage. The use of Reynolds stress as an indicator of hemolysis is considered, and an alternative measure based on viscous dissipation is proposed. It is shown that under simple flow conditions the Reynolds stresses can be related to viscous dissipation. Data from the literature show that the instantaneous viscous shear stress at which hemolysis occurs is similar to the shear stress thresholds obtained from laminar flow studies. Also, the Kolmogorov length scales for most of the turbulent hemolysis studies are similar to the size of a red blood cell. These observations indicate that, for the jet and couette experiments examined, viscous shearing is an important mechanism in the destruction of erythrocytes by turbulence. However, pressure fluctuations may also contribute to damage for these cells and for cells of similar or larger size.

The data are consistent with a model of intimal thickening in which the intimal hyperplastic pannus migrating from the suture line was enhanced by reduced levels of wall shear stress at the PTFE graft/host artery interface. Such hemodynamic modulation of injury induced IHT was absent at the neighboring artery wall.

Low arterial elasticity is associated with stenosis and fistula maturation failure. However, vessel dilatation is not needed for adequate blood flow except at the smaller diameters in this study. We speculate that low elasticity promotes development of stenosis. Larger studies are needed to confirm these promising results and to determine whether therapies directed at improving elasticity can improve maturation.

Flow behavior in models of end-to-side vascular graft anastomoses was studied under steady and pulsatile flow conditions. Models were constructed to simulate geometries employed in experimental studies on intimal thickening in a canine model. Reynolds numbers, division of flow in the outflow tracts and the pulsatile waveform employed were taken from measurements obtained in the canine model. Flows in the scaled-up, transparent models were visualized with white, neutrally buoyant particles which were photographed under laser illumination and also recorded on video tape under bright incandescent light. Strong, three-dimensional helical patterns which formed in the anastomotic junction were prominent features of the flow fields. Regions of low wall shear, oscillatory wall shear and long particle residence time were identified from the flow visualization experiments. Comparisons with the limited qualitative data available on intimal thickening in vascular graft anastomoses suggest a relation between localization of vascular intimal thickening and those surfaces experiencing low shear and long particle residence time.