Amphiphilic nature of polyethylene glycols and their role in medical research

Background: Polyethylene glycol (PEG) is a polyether compound which is an excellent candidate to study possible specific interactions of protein-polymer systems at the atomic level. Such studies would be beneficial in obtaining a more thorough understanding of PEG-protein interactions and might help to explain PEG's effects on protein behavior when used as a crowder. Scope of review: PEGs has been called double edged sword showing assorted effects on the protein due its hydrophilic, hydrophobic and amphiphatic nature. It has been observed that the stabilization of the protein due to PEGs is because of exclusion volume effect (hard core interactions) shown by the higher molecular sizes of the crowder, however there are soft (chemical) interactions also which leads to destabilization of proteins. Most of low molecular size PEGs are noticed to destabilize proteins due to soft interactions. General significance: Here, the core characteristics of the polyethylene glycols that are responsible for the various interactions with proteins and trying to delineate the behaviour of PEGs being ambiguous, are discussed. To conclude its paradox nature being a factual inert molecule or not, many different reports of PEG interactions with various proteins are clubbed together. In addition, owing to low toxicity, high polarity, high water solubility, typically unhydrolysing or undeteriorating characteristics, it has a practical significance in pharmaceutical and cosmetic industries, and in the research field on which this review shall enlighten from earlier to now.