The Interations Between Phospholipid Monolayer And Pluronic Or PEG Cholesterol Ester

Amphiphilic copolymer possesses much particular specificity due to its special structures with hydrophilic and hydrophibic groups.Aqueous amphiphilic copolymer PEO-PPO-PEO, commercially known as Pluronci, is a kind of important nonionic surfactant. Now Pluronic is extensively being studied as drug carrier because its amphiphilic characteristics can be tuned by changing the molecular architecture to meet specific application needs.In this paper Langmuir Balance is used to study the interactions between phospholipid and Pluronic or synthesized mPEG ester. In order to systematically understand the interactions, the mixed monolayers and the absorbed monolayers were employed.First, for simulating the half biomembrane, cholesterol/phospholipid mixed monolayers were studied. The mixed thermodynamics parameters, excess molecular area and excess Gibbs free energy were caculated from the p～A isotherms. The results show that phospholipid and cholesterol are miscible and cholesterol can increase the fluidity of phospholipid membrane.Secondly, the interficial properties of Pluronics L61, L62, L64, F68, F108, L101, F127 and F88 were studied. The p-A isotherms indicate that, the physical properties of the films is mainly determined by the PEO chains at low cover density while PPO chains make the conformations and determine the monolayer properties at high surface pressure.Thirdly, the inteactions between Pluronic and phospholipid were studied. By analysing the different mixed spreading monolayers, the conclusion we can be drawn that the longer the PPO chains of Pluronic, the stronger its interations with phospholipid. With the increase of the PEO chains, the interactions of Pluronic with subphase also increase at high surface pressure. The investigation of the phospholipid monolayers absorbed by Pluronics suggested that, Pluronics with higher hydrophbolicity manifested higher penetration ability to phospholipid monolayers.Finnaly, three kinds of mPEG cholesterol esters with different molecular weight were synthesized and characterized. Their surfacial properties and the interactions between them and phospholipid were also studied by Langmuir Balance. It was found that the longer the PEG chains, the stronger interactions of mPEG cholesterol esters with phospholipids in the mPEG cholesterol esters/phospholipid mixed monolayers. But in the adsorption process, the long PEG chains may prevent the interactions of mPEG cholesterol esters with phospholipid.