What Are PEGs?

PEGs (polyethylene glycols) are composed of polyether compounds repeating ethylene glycol units according to the constituent monomer or parent molecule (as ethylene glycol, ethylene oxide, or oxyethylene) (Fig. 1). Most PEGs are commonly available commercially as mixtures of different oligomer sizes in molecular weight (MW) ranges. For instance, PEG-10,000 typically designates a mixture of PEG molecules (n = 195 to 265) having an average MW of 10,000.

PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), with the three names being chemical synonyms. However, PEGs mainly refer to oligomers and polymers with molecular masses below 20,000 g/mol, while PEOs are polymers with molecular masses above 20,000 g/mol, and POEs are polymers of any molecular mass.

What Are PEGs Used for?

PEG compounds have many applications. In the pharmaceutical industry, for instance, they are used as ointment bases or vehicles for drugs in capsules, tablet and pill binders, suppositories, and liquid prescriptions; and in veterinary drugs as part of parenteral, topical, ophthalmic, oral, and rectal preparations. Further various applications were found in soaps and detergents, wood preservation, printing, chemical mixtures, as well as in industries that produces textiles, leather, plastics, resins, paper, ceramics, glass, rubber, petroleum, and metal. Polyoxyethylene sorbitan esters (polysorbates) and polyethylene glycol, with an average molecular weight of 6,000, are permitted as food additives in various food products. They can also be used in cosmetics.

Are PEGs safe in Cosmetics?

PEGs are products of condensed ethylene oxide and water that can have various derivatives and functions. Since many PEG types are hydrophilic, they are favorably used as penetration enhancers, especially in topical dermatological preparations. PEGs, together with their typically nonionic derivatives, are broadly utilized in cosmetic products as surfactants, emulsifiers, cleansing agents, humectants, and skin conditioners. Currently, PEG-20 glyceryl triisostearate and PEGylated oils are considered safe for cosmetic use according to the results of relevant studies.

Why Are PEGs used in Drug Delivery?

Polyethylene glycol is widely utilized in drug delivery and nanotechnology due to its reported “stealth” properties and biocompatibility. It is generally thought that PEGylation allows particulate delivery systems and biomaterials to evade the immune system and thereby prolong circulation lifetimes.

Is PEG biodegradable?

Many synthetic biomaterials, including the widely applied polyethylene glycol and essentially all polymers derived from radical polymerization reactions comprising a CeC polymer backbone are considered non-biodegradable. However, in the study of On the biodegradability of polyethylene glycol, polypeptoids and poly(2-oxazoline)s, the researchers have present evidence that PEG, POx and POI are degradable by oxidative degradation under biologically relevant conditions. While the researchers do not envision oxidative degradation to be of relevance in the short-term usage of these polymers, mid- and long-term biodegradability in vivo appears feasible.

Is PEG Environmentally Friendly?

Polyethylene glycol is an eco-friendly solvent. Various metal-catalyzed carbon–carbon bond formation reactions can conduct in PEG. Metal-PEG system can readily recover and reuse.

References

1. Jang HJ, et al.; Safety evaluation of polyethylene glycol (PEG) compounds for cosmetic use. Toxicological research. 2015, 31(2):105-36.
2. Verhoef JJ, Anchordoquy TJ. Questioning the use of PEGylation for drug delivery. Drug delivery and translational research. 2013, 3(6):499-503.
3. Ulbricht J, et al.; On the biodegradability of polyethylene glycol, polypeptoids and poly (2-oxazoline) s. Biomaterials. 2014, 35(17):4848-61.