Polyethylene glycol is a linear chain structure consisting of repeating oxyethylene groups with a hydroxyl group at each end. It can be formed by the stepwise addition polymerisation of ethylene oxide and water or ethylene glycol. Polyethylene alcohol is a water-soluble polymeric compound with a molecular weight of M = 18+44n. The physical form is different due to different molecular weights. The molecular weight is 200~800, which is a colorless, odorless, non-volatile and viscous liquid at room temperature and is slightly water absorbing; the molecules are waxy semi-solid at 1000 ~ 2000; the molecular weight is 3000 ~ 20000 and gradually turns into hard light white waxy solid or flaky paraffin or liquid powder. As the molecular weight increases, its water solubility, vapor pressure, toxicity, water absorption and solubility in organic solvents decrease accordingly, while the relative density of freezing point, flash point and viscosity increase accordingly. It is heat stable, inert to many chemicals and does not hydrolyze. Polyethylene glycol with a molecular weight above 4,000 is neutral, has good biocompatibility and is safe for the human body. Polyethylene Glycol Series products are low toxicity, non-irritating, have good water solubility and good compatibility with many organic components such as alcohols, ketones, chloroform, glycerides and aromatic hydrocarbons; they are insoluble in most aliphatic hydrocarbons and ethers. Polyethylene glycol is widely used in the cosmetic, pharmaceutical and biomedical fields because it has many excellent properties such as water solubility, non-volatility, moisturizing, dispersibility, physiological inertness, mildness, lubricity and skin moisturizing and softening.
Figure 1. Conjugating a specific polymer such as polyethylene glycol (PEG) to liposomes. (Rommasi F, et al.; 2021)
In addition, polyethylene glycol's excellent biocompatibility allows it to dissolve in the body's tissue fluid and be rapidly eliminated from the body without side effects. Less commonly, when polyethylene glycol is coupled with other molecules, many of its excellent properties are transferred to the conjugate. As a result, its use in medicine has received widespread attention and has been recognized by the US Food and Drug Administration (FDA). In the pharmaceutical industry, polyethylene glycol can be used as a drug excipient to improve various properties of drugs such as dispersibility, film forming, lubricity, sustained release, etc.; polyethylene glycol is also used as a matrix for ointments, emulsions, salves, lotions and suppositories. PEG has a wide range of compatibility and can be used as a vehicle and adhesive for many pharmaceutical preparations. Once cross-linked, polyethylene glycol can absorb 10 to 100 times its own weight in water and release it as required. Taking advantage of this property, it can be used as a highly absorbent resin. Polyethylene glycol can also be used in many other areas, such as drug carriers and medical dressings. This is mainly because it is relatively easy to modify. For example, the use of polyethylene glycol in the synthesis and modification of new biomaterials will impart new properties and functions to the materials, such as hydrophilicity, anticoagulant properties and anti-macrophage phagocytosis. Studies have shown that in the application of polyethylene glycol and its derivatives, the end groups of the polymer molecule play a role in determining its use, and polyethylene glycol with different end groups has different uses. Studies have shown that the ends of polyethylene glycol polymer chains can not only be hydroxyl groups, but also other more reactive functional groups can be introduced by chemical reactions, such as amino groups, carboxyl groups, azido groups, etc. can be introduced at both ends of the polyethylene glycol chain. The introduction of these functional groups has greatly expanded the range of applications of polyethylene glycol in organic synthesis, peptide synthesis, sustained and controlled release of drugs, targeted drug delivery, etc.
Azide-amine-poly(ethylene glycol)-COOH is a trifunctional polyethylene glycol derivative. The polymer has an amine and an azide group at one end and a carboxyl group at the other end. Polyethylene glycol with an amine group can react with carboxylic acids and their active esters, isocyanates and can also react with carbonyl groups such as ketones and aldehydes. The azide group can be used for azide "click" chemistry under mild conditions, which is very useful for bioconjugation. The polyethylene glycol carboxyl group can react with amines or OH-containing moieties.
Alternate Names:
Azido Amine-PEG-COOH
Azide-PEG-NH2-COOH
Azido-PEG-NH2-COOH
Azido-PEG-Amine-COOH
Azide-PEG-Aminocarboxylic Acid
Azido-PEG-NH2-COOH
Azide-PEG-Carboxylate-NH2
References:
1. Rommasi F, Esfandiari N. Liposomal Nanomedicine: Applications for Drug Delivery in Cancer Therapy. Nanoscale Res Lett. 2021, 16(1):95.
2. Maruyama K. PEG-immunoliposome. Biosci Rep. 2002, 22(2):251-66.
Poly(ethylene glycol) block copolymers
J Biotechnol.
Authors: Tirelli N, Lutolf MP, Napoli A, Hubbell JA.
Abstract
The ubiquitous use of poly(ethylene glycol) in the biomaterials field has also boosted the research activity in the chemical derivatization of this polymer. We focused our interest on the preparation of tailor-made poly(ethylene glycol)-based structures and on the study of structure-activity relationships for its functionalization, as preliminary steps for the preparation of smart functional materials. More specifically, amphiphilic and cationic block copolymers were prepared for prospective use in the preparation of self-assembled carriers, and Michael-type addition of thiols onto acrylates was studied as a model for end-group reaction leading to hydrogel formation.
Poly(ethylene glycol)-poly(lactic-co-glycolic acid) based thermosensitive injectable hydrogels for biomedical applications
J Control Release.
Authors: Alexander A, Ajazuddin, Khan J, Saraf S, Saraf S.
Abstract
Stimuli triggered polymers provide a variety of applications related with the biomedical fields. Among various stimuli triggered mechanisms, thermoresponsive mechanisms have been extensively investigated, as they are relatively more convenient and effective stimuli for biomedical applications. In a contemporary approach for achieving the sustained action of proteins, peptides and bioactives, injectable depots and implants have always remained the thrust areas of research. In the same series, Poloxamer based thermogelling copolymers have their own limitations regarding biodegradability. Thus, there is a need to have an alternative biomaterial for the formulation of injectable hydrogel, which must remain biocompatible along with safety and efficacy. In the same context, poly(ethylene glycol) (PEG) based copolymers play a crucial role as a biomedical material for biomedical applications, because of their biocompatibility, biodegradability, thermosensitivity and easy controlled characters. This review stresses on the physicochemical property, stability and composition prospects of smart PEG/poly(lactic-co-glycolic acid) (PLGA) based thermoresponsive injectable hydrogels, recently utilized for biomedical applications. The manuscript also highlights the synthesis scheme and stability characteristics of these copolymers, which will surely help the researchers working in the same area. We have also emphasized the applied use of these smart copolymers along with their formulation problems, which could help in understanding the possible modifications related with these, to overcome their inherent associated limitations.
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