Preparation And Molecular Transport Properties Of DOPG And PCDA Binary Vesicles

Biological membranes interface,especially cell membrane interface,involves a variety of physiological processes such as material transport,signal transduction and protein adsorption and desorption.Therefore,in situ real-time detection of the structure and function of phospholipid molecules in natural or artificially prepared cell membranes and the dynamic behavior of drug/dye molecules on their surface interface can help us understand the process of biological system medium transport and improve vesicles The design of drug delivery system is very important.In this paper,we studied the relative phase problem between 4-(4-diethylaminostyryl)-1-methyl-pyridinium iodide(D289)and water molecules at the interface of 10,12-pentacosadiynoic acid(PCDA)vesicles and 1,2-dioleoyl-snglycero-3-phosphate-rac-(1-glycerol)sodium salt(DOPG)vesicles.The second harmonic generation(SHG)signals of D289 molecules adsorbed on DOPG and PCDA vesicles were determined by measuring and analyzing the changes of SHG signals.It was considered that the phase of D289 molecules adsorbed on DOPG and PCDA vesicles was the same as that of water molecules at the vesicle interface.A clear understanding on the structure and functionality of lipid molecular on the natural or artificial cell membranes are important yet hard to achieve.In this work we compared the adsorption and transportation of a dye molecule(D289)on the surface of DOPG and PCDA lipid vesicles,as well as the binary complex vesicles with in-situ second harmonic generation technique.It was observed that the dynamics of the cross-membrane transportation of D289 varied significantly with the composition of the vesicle membrane.Even for the vesicles prepared with the same PCDA/DOPG ratio as 7/3,the experiments showed notable variations in the vesicles prepared at different batches.Randomly generated molecular domains at the vesicle surface during the formation of the binary complex vesicles is the most possible explanation to the experimental observations.Two possible cross-membrane transportation mechanisms are also presented.In this paper,the effect of salt ion on the dynamic behavior of D289 molecules on the surface of complex vesicles was studied.The molecular structure of the complex vesicles and the transfer process of molecules on the surface interface were further discussed.The dynamic behavior of D289 molecules at the interface in single component and different ratio vesicular salt solutions was detected by second harmonic technique.On the one hand,the relative phase of D289 and water molecules on the interface of vesicles is discussed,and the orientation of the interaction between D289 and phospholipid membrane is clarified.On the other hand,the second harmonic technique is used to study the molecular dynamics at the interface of the complex vesicle membrane.Considering the influence of the vesicle solution environment on the process,it is helpful to understand the molecular structure and the molecular transmembrane transmission mechanism of the complex vesicle structure domain,which is of guiding significance for the design of multi-component vesicle drug loading system.