Main Applications of Polyethylene Glycol (PEG) (Part One)
What is Polyethylene glycol?
Polyethylene glycol (PEG) is a biocompatible, synthetic, hydrophilic polyether compound that has many applications, mostly in the medical industry, but also in the chemical and industrial sectors. The structure of the compound is known as H−(O−CH2−CH2)n−OH. It is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight.
What are the uses of Polyethylene glycol?
- Medical uses
PEG is the basis of a number of laxatives. Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy.
PEG is also used as an excipient in many pharmaceutical products.
When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood.
The possibility that PEG could be used to fuse axons is being explored by researchers studying peripheral nerve and spinal cord injury.
An example of PEG hydrogels (see "Biological uses" section) in a therapeutic has been theorized by Ma et al. They propose using the hydrogel to address periodontitis (gum disease) by encapsulating stem cells in the gel that promote healing in the gums. The gel and encapsulated stem cells was to be injected to the site of disease and crosslinked to create the microenvironment required for the stem cells to function.
A PEGylated lipid is used as an excipient in both the Moderna and Pfizer–BioNTech vaccines for SARS-CoV-2. Both RNA vaccines consist of Messenger RNA, or mRNA, encased in a bubble of oily molecules called lipids. Proprietary lipid technology is used for each. In both vaccines, the bubbles are coated with a stabilizing molecule of polyethylene glycol.[medical citation needed] As of December 2020 there is some concern that PEG could trigger allergic reaction,[7] and in fact allergic reactions are the driver for both the UK and Canadian regulators to issue an advisory, noting that: two "individuals in the U.K... were treated and have recovered" from anaphylactic shock.[8][9] As of 18 December, the US CDC stated that in their jurisdiction six cases of "severe allergic reaction" had been recorded from more than 250,000 vaccinations, and of those six only one person had a "history of vaccination reactions".
- Chemical uses
Because PEG is a hydrophilic molecule, it has been used to passivate microscope glass slides for avoiding non-specific sticking of proteins in single-molecule fluorescence studies.
Polyethylene glycol has a low toxicity and is used in a variety of products. The polymer is used as a lubricating coating for various surfaces in aqueous and non-aqueous environments.
Since PEG is a flexible, water-soluble polymer, it can be used to create very high osmotic pressures (on the order of tens of atmospheres). It also is unlikely to have specific interactions with biological chemicals. These properties make PEG one of the most useful molecules for applying osmotic pressure in biochemistry and biomembranes experiments, in particular when using the osmotic stress technique.
Polyethylene glycol is also commonly used as a polar stationary phase for gas chromatography, as well as a heat transfer fluid in electronic testers.
PEG has also been used to preserve objects that have been salvaged from underwater, as was the case with the warship Vasa in Stockholm, and similar cases. It replaces water in wooden objects, making the wood dimensionally stable and preventing warping or shrinking of the wood when it dries. In addition, PEG is used when working with green wood as a stabilizer, and to prevent shrinkage.
PEG has been used to preserve the painted colors on Terracotta Warriors unearthed at a UNESCO World Heritage site in China. These painted artifacts were created during the Qin Shi Huang (first emperor of China) era. Within 15 seconds of the terra-cotta pieces being unearthed during excavations, the lacquer beneath the paint begins to curl after being exposed to the dry Xi'an air. The paint would subsequently flake off in about four minutes. The German Bavarian State Conservation Office developed a PEG preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers.
PEG is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
PEG derivatives, such as narrow range ethoxylates, are used as surfactants.
PEG has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.
PEG has also been used as a propellent on the UGM-133M Trident II Missile, in service with the United States Air Force.
To be continued in Part Two…
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