Preparation of polyethylene glycol PEG for fusion

PEG is melted and sterilized by autoclaving, cooled to 50 C (still liquid) and combined with an equal volume of PBS, pH 7.0. Since 1 g PEG gives very close to 1 ml, this produces a 50% (w/v) solution. The PEG solution can be stored frozen. 

The optimum concentration of PEG (30-50%) for fusion is very close to the toxic concentration (at or above 50%). Toxicity of the different batches of PEG may vary considerably. It can be advantageous to include 5% dimethylsulfoxide (DMSO) in the PEG preparation (Norwood et al., 1976 Fazekas de St. Groth and Scheidegger, 1980). 

---