Endotoxins (~10-1000kDa) are structural components of bacteria (LPS is the best known) that are released from bacteria when they die. Endotoxins cause inflammatory responses in humans and animals (infections give you a fever) and in cultured cells. For most cell culture applications, you don’t have to worry too much about endotoxins. For monolayer permeability experiments,…
I’ve been growing brain endothelial cells on PET and pnc-Si membrane transwells for a variety of experiments, but mainly to measure the TEER (transendothelial electrical resistance). TEER is used to track the integrity of cell monolayers grown on permeable supports. As the monolayer gets ‘tighter’, the TEER increases. PET membranes are marketed as transparent for…
Over the past month, I’ve posted some results of a colorimetric assay for silicic acid. Previous posts are here and here. These results showed that the assay detected silicic acid after pnc-Si and PSi degraded. However, bare silicon wafers also yielded silicic acid, according to this assay. Since pnc-Si samples have the Si well-side surface,…
A few weeks ago, I posted discoloration results on carbonized membranes here. It was 6 weeks yesterday since I started this experiment, so I decided to stop it (few, if any, cell applications require 6-weeks of culture). These were SC141 chips in the flat (not transwell) format. I also used DMEM with high NaHCO3 levels. …
I repeated the first degradation experiment (posted here) to confirm the results. I also tracked discoloration of the samples this time. As before, I used 1X PBS, but this time, the entire assay was performed in the 37C oven. Discoloration pictures: The PSi sample starts with a new rainbow coloration and then completely discolors to…
Anant and I found a protocol in Biomaterials a few weeks ago that allows colorimetric determination of silicic acid. It was used to track the degradation of PSi samples in Tris-HCl buffer. I optimized this protocol and got standard linear curves, as reported in the protocols section of the blog here. Here, I report the…
I finally got some MATLAB code working which calculates permeability coefficients (P, in cm/s) from a non-sink, generalized equation. This data is from (n=5) fluorescein (MW~370 Da) transport experiments in the Tecan (time vs. receiver well concentration (Cr) values). In this first set of data, I used polycarbonate and polyester transwells, at room temperature, without…
Dave gave me some carbonized samples several weeks ago to test stability/discoloration. I measured the contact angles right after I got the samples (posted here) and then started the discoloration. These are SC141 chips. Controls were untreated (1st column) and RTP’ed only (2nd column) chips. Two carbonization conditions were tested – 5 minutes of 1…
To supplement the work that Dave’s been doing with carbonization, I’m doing some chemical stability/discoloration tests. The first step of these tests is to measure the contact angles. The following are images of contact angle tests and quantitative data from ImageJ of the angles. These are SC141 chips and they are not rinsed or treated…
Tom gave me a few samples to scan on the AFM. PVP was added to the well side of the samples. I scanned the pnc-Si side of the chips to see if/how the PVP came through the pores. Samples were from SC114. Two different areas of supported pnc-Si membrane on control (no PVP) chip: The…