Polyethylenimine (PEI), branched (1 mg/mL)
MATERIALS
Equipment
Rinse all glassware three times with high-purity H2O.
Cylinder, graduated, 500-mL
Pipette, serological, graduated, 5-mL
Tube, conical, 50-mL
Tube heater or water bath preset to 50°C
Vacuum filtration unit, 0.22-μm
METHOD
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1. Dip a 5-mL pipette into the PEI stock and drip 500 mg of branched PEI liquid drop-wise directly into a 50-mL conical tube. Add 30 mL of H2O.
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2. Heat the mixture to ~50°C. Mix by shaking until completely dissolved.
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3. Add H2O to a final volume of 50 mL. Mix again.
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4. Pour 50 mL of the solution into a 500-mL graduated cylinder. Adjust the final volume to 500 mL with H2O.
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5. Filter-sterilize the solution through a 0.22-μm membrane.
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6. Store aliquots of the desired volume at -20°C.
