Year: 2005
Type: article
Abstract: PEO-PPO-PEO copolymers are symmetric nonionic amphiphilic triblock copolymers with poly (ethylene oxyde), PEO, as the hydrophilic end blocks and poly (propylene oxyde), PPO, as the hydrophobic middle block: PEO-PPO-PEO copolymers are commercially available in a range of molecular weights (PEO and PPO block length) and copolymer composition (PPO/PEO ratio). As a result, PEO-PPO-PEO copolymers have different physicochemical properties and find widespread industrial applications. The aim of this work was to focus on specialized pharmaceutical applications. PEO-PPO-PEO copolymers are found to be an efficient drug delivery system with multiple effects. The single molecular chain of copolymer, unimers, inhibit drug efflux transporters in both the blood-brain barrier and in the small intestine, which provides for the enhanced transport of select drugs to the brain and increases oral bioavailability. Furthermore, the interactions of the unimers with multidrug-resistant cancer cells results in sensitization of these cells with respect to various anticancer agent. Due to the amphiphilic nature of PEO-PPO-PEO copolymers they are able to self-aggregate to form variety of associated structures such as micelles and liquid crystalline phases. The micelles formed in aqueous solutions consist of a hydrophobic core of PPO and hydrophilic corona of PEO. The interesting feature of the block copolymer micelles is that they remain stable for longer time, even when the concentration is reduced below the critical micelle concentration (crne). Another characteristic property of PEOPPO- PEO block copolymer systems is the thermoreversible gelation displayed by some concentrated block copolymers at temperatures close to room temperature. Both the micellisation and gelation are affected by range of factors such as temperature, copolymer composition, molecular weight, concentration, and presence of cosolutes (surfactants, electrolytes, and hydrophobic substances). The incorporation of drugs into the micelles or gels can improve solubility, reduce hydrolytic/metabolic degradation, achieve sustained release, and result in imporoved bioavailability. The toxicity of PEO-PPO-PEO copolymers bave been investigated for different pharmaceutical applications and found to be quite low. However, the toxicity of these copolymers is a complex issue and therefore; the toxicological aspects have to be considered from each formulation perspective.
Author: Ivan Pepić
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2753380775