Mechanistic Study Of The Dynamic Adsorption Behavior Of Lycium Barbarum Polysaccharides On Lipid Monolayers

Lycium barbarum polysac charie is mostly composed of the Chinese wolfberry.LBP possess high pharmacological activity,including immune activation,anti-tumor,antiviral,anti-radiation,as well as hypoglycemic and hypolipidemic,neuroprotection effects.LBP,as the natural medicine and food,which still have attracted much attention of medicine and food homologous plants.Lycium barbarum polysaccharide is used in the prevention and treatment of various diseases,and all has achieved remarkable results.Howerver,the specific mechanism of its biological activity is still unclear and needs to be further explored.Therefore,Our results provide new insights on the pharmacological mechanism and the therapeutic benefits of LBP.These findings lay the foundation for exploring the pharmacological mechanism of LBP as an in vivo therapeutic.It is of great significance to study the interaction between Lycium barbarum polysaccharide and biomacromolecule in exploring its mechanism and clinical application.In this work,the the adsorptive behavior of Lycium barabrum polysaccharides(LBP)on unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)?saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC)of the single system,and POPC/DPPC of the binary system,POPC/DPPC/Cholesterol(Cholesterol)of the ternary system lipid monolayer films were investigated at the air/water interface by the mothods of preparing monolayer film with the Langmuir films and atomic force microscopy(AFM)technique,respectively.It provides a certain theoretical and experimental basis for studying the detailed mechanism of polysaccharide biological activity.The experimental contents and results are as follows:(1)The interaction between LBP and the monolayer films of the single system.According to the changed LBP concentration,the ?-A isotherms?the ?-t adsorption curves?the compression modulus curves?the images of AFM and the Ap values were obtained.The experimental results indicated that:It is obviously different adsorption behaviors of LBP on the POPC?DPPC lipid monolayer films.With the increase in the LBP concentration to the subphase,?-A isotherms of the mixed monolayers shifted to larger molecular areas.The compression modulus showed that LBP decreased the compressibility of the monolayer films.Adsorption curves revealed that the variation in the surface pressure of LBP with POPC was larger than that with DPPC.The degree of LBP adsorbed into the POPC monolayer was higher than that of DPPC.The effect of LBP on the morphological character and adsorption bahavior of the lipid monolayer films was proved by the AFM images.The interaction between LBP and the lipid monolayer films was also verified by Ap values.LBP was embedded and interacted with the fatty acid tail chains of phospholipids through hydrophobic interactions,and the force of POPC was stronger than that of DPPC.It was attributed to the different saturation levels of the fatty acid tail chains of POPC and DPPC,leading to different adsorption behaviors of LBP with the lipids.LBP also interacted with phospholipids via van der Waals forces.(2)The interaction between LBP and the monolayer films of the binary system.According to the changed LBP concentration,the ?-A isotherms?the ?-t adsorption curves?the compression modulus curves?the parameter of the interaction(The excess per molecular area(?Aexc)?excess Gibbs free energy of mixing(?GmixExc)?Ap?the speed of adsorption(K)?the surface excess concentration(?)?the area per molecule(A))and the images of AFM were obtained.The experimental results indicated that:With the increase in the LBP concentration,?-A isotherms of the mixed monolayers shifted to larger molecular areas.Adsorption curves revealed that the variation in the surface pressure was larger in the low and high surface pressure.The degree of LBP adsorbed into the POPC/DPPC monolayer was higher than that of POPC/DPPC/Chol.The excess per molecular area and the excess Gibbs free energy of mixing suggested that it showed the repulsive interaction between POPC and DPPC molecules.Moreover,with the addition of LBP,the repulsion interaction between POPC and DPPC molecules increased.The interaction between LBP and lipid molecules was also verified by the specific values of K?Ap?and A.The AFM images revealed that LBP adsorbed onto POPC/DPPC monolayer film by hydrogen bond and the Van der Waals interaction.(3)The interaction between LBP and the monolayer films of the ternary system.According to the changed LBP concentration,the ?-A isotherms?the ?-t adsorption curves?the compression modulus curves?the parameter of the interaction(The excess per molecular area(?Aexc)?excess Gibbs free energy of mixing(?GmixExc)?A?the speed of adsorption(K)?the surface excess concentration(?)?the area per molecule(A))and the images of AFM were obtained.The experimental results indicated that:With the increase in the LBP concentration to the subphase,?-A isotherms of the mixed monolayers shifted to larger molecular areas.For the low and high surface pressure,the variation in the surface pressure was larger.?Aexc and ?GmixExc suggested that it showed the repulsive interaction between POPC and DPPC molecules.Moreover,with the addition of LBP,the repulsion interaction between POPC and DPPC molecules increased.Since the addition of cholesterol,the repulsive interaction between POPC and DPPC was obviously decreased and the adsorptive ability of LBP on the POPC/DPPC monolayer film was also attenuated.These results were proved by the K?Ap???A values and the AFM images.Thus,cholesterol could affect spontaneous insertion of LBP into the POPC/DPPC monolayer films from phosphate buffer solution.It provides new insights on the pharmacological mechanism and the therapeutic benefits of LBP.Therefore,the interaction of between Lycium barbarum polysaccharides and lipid monolayer films was explored,and the addition of cholesterol could affect the adsorption behavior of Lycium barbarum polysaccharide on the lipid monolayer films.The mechanism of both Lycium barbarum polysaccharides and lipid monolayer films was explained qualitatively and quantitatively.It provides new insights on the pharmacological mechanism and the therapeutic benefits of LBP.Cholesterol could protect the cell membrane from the effects of Lycium barbarum polysaccharide to a certain extent.