I’ve been trying to get multi-color images of endothelial cells and glial cells on transwell membranes in order to compare image quality on glass, pnc-Si and polymer membranes.  Specifically, I’ve tried staining endothelial cells green with VEGF mAbs and glial cells red with neurofulament H (NFH) mAbs but VEGF expression in bEnd3 cells is extremely…

Those with a great memory will remember that I’ve been struggling (1, 2, 3) to identify adherens and tight junction proteins (i.e., cadherins and ZO-1) in bEnd3 endothelial cells.  Since I’ve recently moved over to investigate air-blood barrier co-culture models, I decided to see if my epithelial cells (RLE-6TN) express cadherins (they should since these…

This figure is a potential response to Reviewer’s 1 question about the difference between pore discovery and transmembrane resistances and Reviewer’s 2 question about membrane vs. well resistance. a.  Resistances for an ultrathin membrane with large pores.  The pore discovery resistance is larger than the transmembrane (steric/frictional) resistance for small molecule sizes.  The total resistance…

Our collaboration with Alison Elder, et al. in the Dept. of Environmental Medicine has led us to talk about developing a co-culture model of the air-blood barrier.  This barrier is ‘located’ at the alveolar sacs in the lungs, where lung epithelial cells in the alveolar space are exposed to air.  These epithelial cells are separated…

One of the reviewers for the diffusion based separations paper was concerned that there would be osmotic pressure which would cause convection across the membrane.  Previously we have been aware of osmosis in the DNA experiments by Paul Black and Bill Bernhard, although their results were due to a salt imbalance if I recall correctly….

In an attempt to address the Nano Letters reviewer’s comment (show molecular separation, not just Au), I ran a simple experiment where I tried to pass BSA, Cyt. C, IgG, and β-galactosidase through carbonized membranes in the pressure cell. We have to be careful in calling this a “separation” since the two different species were never…

You can use any electrokinetic phenomena to determine zeta potential since they’re all related.  Here I’ve determined the zeta potential of untreated (non), plasma oxidized (ox), and silanized (asi) samples using both streaming potential measurements and electroosmotic flow rates. These measurements seem to follow the same trend, although the EO is lower in all cases….

I dug out some of my old data and found this comparison for 3x and 6x window flow rates at different voltages (minimal repeats, error bars not included): This shows that as voltage goes up, the flow rate increases for each of the active areas shown here.  Obviously if we were to publish this we’d…

Last week, I calculated the Young’s modulus and residual stress of several different membranes using the pressure-displacement technique. The measurements were performed on at least three different geometries (square and rectangle) and the results were averaged. Wafer Thick. (nm) Por. (%) Anneal Res. Stress (MPa) Young’s modulus (GPa) 532 15 2.59 1000 sus 4.17 31.67…

Pnc-Si membranes have a high rate of EO pumping, but what is the best way to compare to other pumps?  The initial figure we used is an updated version of a figure found in a paper about alumina EO pumps (original figure bottom of this post).  In this figure we show flow rate normalized to…