Polycarbonate track-etch (PCTE) membranes are the primary type of filters used in our chambers and instrument systems. This is a very thin membrane ranging between 6-10µm in nominal thickness. This membrane type offers excellent uniformity in pore size and density, as well as other benefits such as low extractables, low protein binding, and negligible absorption. These characteristics make it ideally suited for use in chemotaxis assays as well as other high purity screening assays.
PVP Treatment –PCTE membranes are available pre-treated with the wetting agent polyvinylpyrrolidone (PVP) which makes the surface hydrophilic. PVP-treated membranes are used when the media solutions cannot wet out the membrane by themselves. This occurs primarily when working with very small pore sizes or high viscosity media solutions. Certain cell types such as neutrophils do not adhere well to PVP treated membranes and tend to drop off after migrating. While this is problematic when quantifying filters on the membrane, some researchers using the ChemoTx® sytem or the MB-series 96-well chambers and quantifying in the plate find this to be an advantage. Extra-cellular matrix proteins do not adhere well to PVP treated membranes either. If your assay requires such coating, we recommend using PVP-free membranes.
Polycarbonate membranes are available in the following pore sizes and corresponding pore densities:
| Pore size (+0/-20%) | 2µm | 3µm | 5µm | 8µm | 10µm | 12µm | 14µm |
|---|---|---|---|---|---|---|---|
| Density (pores/mm2) (tolerance +/- 15%) |
2 x 104 | 2 x 104 | 4 x 103 | 1 x 103 | 1 x 103 | 1 x 103 | 5 x 102 |
Many factors other than cell type enter into the pore size selection process. Please see our page on Experiment Design. Please see the charts below for pore size availability for specific products.
The ChemoTx® disposable system and the reusable 96-well chambers use relatively large pieces of PCTE membrane that are difficult to handle by themselves. For convenient handling, these instruments use filters bonded to anodized aluminum frames, referred to as “framed filters.” Framed filters with adhesive (Stock# ending in “/A”) are available for use in the MB series chambers only. The adhesive makes it possible to remove the microplate from the chamber with the filter still attached for spinning in a centrifuge.
Framed Filters with or w/o adhesive for MB-series 96-well chambers
Sold in boxes of 15.
| Pore Size | 2µm | 3µm | 5µm | 8µm | 10µm | 12µm |
|---|---|---|---|---|---|---|
| Standard | — | PFD3 | PFD5 | PFD8 | PFD10* | PFD12* |
| With adhesive | — | – | PFD5/A | PFD8/A | PFD10/A* | PFD12/A* |
| PVP treated | PRD2 | PRD3 | PRD5 | PRD8* | — | — |
| PVP w/adhesive | PRD2/A | PRD3/A | PRD5/A | PRD8/A* | — | — |
*non-stock items, call for availability
The Standard and Specialty series of multiwell chambers and the single well chambers use punched filters in a variety of sizes. They are available with standard untreated surface or with the wetting agent polyvinylpyrrolidone (PVP).
Filters for the AP48, AC48, AA12 and AA10 are also available in cellulose nitrate. These are much thicker (~150 µm) fibrous filters, sometimes referred to as “torturous path” filters. Rather than counting cells that have migrated through the membrane, as is commonly done with PCTE membrane, these filters are clarified with solvents after a predetermined incubation, and a high-resolution light microscope is used to observe how far into the filter the cells have migrated. This is also known as a “leading edge” study. These filters have a recommended shelf life of one year. They are cut to order, so please allow 2-3 days for processing.