Binding Properties

Since many cell culture media components are heat-sensitive and chemical sterilization methods may leave unwanted by-products, membrane filtration is often the method of choice for sterilizing high value biotechnology products, such as tissue culture media and expensive protein additives.

Researchers must be confident that when these solutions are filtered, either to ensure sterility or to remove particulates, the proteins are not lost.

Because the internal surface area of polymeric microporous membranes is 100–600 times as great as the frontal surface area, there is a vast internal surface area accessible to proteins. Since the nonspecific binding (NSB) of proteins may affect the recovery of expensive final product, selecting the “best” membrane filter is a top priority.


Depending on the filter type, the thickness of membrane filters ranges from 10 to 170 µm. Conversely, depth filters can range between 100 and 500 µm in thickness.

Thickness of membranes is measured using gauges with a resolution of 1 to 2 microns. Care is taken to ensure that the membrane is not crushed during the measurement.


Pyrogens are fragments of bacterial cell walls. When injected into the body, pyrogens can elicit a fever response in humans. Pyrogens result from bacterial contamination in the manufacturing process, the post-manufacturing process, or from packaging. Because they do not represent functional cells, pyrogens cannot be identified in a contamination test for bacteria. Rather, they are compounds that sit on the filter surface and can be released as the filtrate stream passes through the filter