Poly (ethylene glycol) (PEG) is non-ionic hydrophilic and non-toxic polymer. It is widely used in the emerging field of polymerA€based drug delivery. PEG is available in different molecular weights. It facilitates the purification and crystal growth of proteins and nucleic acids. PEG and dextran together result in aqueous polymer two phase system which is required for the purification of biological materials. It also interacts with cell membrane thereby allowing cell fusion.