I have some poly L lysine which isn't sterile (we use it to coat slides por microscopy) and I would like to use some for cell culture, so my cells can attach to the culture bottle.
You can make a solution of known strength of poly-L-lysine aqueous solution and sterile filter using Millipore filtration unit in aseptic condition. Try 0.2micron syringe driven filters. you can find catalog number in the attached brochure.