Problem with Linear PEI 25 kda - (Feb/19/2012 )
I am working in gene delivery laboratory and i am using linear PEI (25 kda) to do the transfection on cancer cells. I had problem dissolving linear PEI of 25 kda MW in water.But in literature many people stated that they prepared stock solution in distilled water. Can anyone suggest me that how can i dissolve it in water
A colleague gave us a protocol that has worked well for our transfections. The linear PEI (25,000 m.w.) is dissolved in boiling hot water at a concentration of 1 mg/ml.
Linear PEI is soluble in hot water, cold water at low pH (that may be your problem), methanol, ethanol and chloroform. It's insoluble in benzene, ethyl ether, aceton and cold water (physiological pH).
PEI can be toxic to cells, so you'll need to titrate the amount of PEI to use for a successful transfection (10 ul for a 6 well plate or 35 mm dish is a good start point). You may also need to remove the PEI-DNA solution after 3 hours to prevent the PEI from killing off all your cells. Not all cell types are damaged by PEI, so monitor the health of your cells after you add the transfection mixture and change to regular media if the cells look really sick.
As an alternative to making your own, there is the PEI-based transfection reagent ExGen 500 from Fermentas (distributed by Thermo-Fisher in North America). It works well for our cell lines and they have a list of cell types that the reagent has been tested on.