Preparation And Properties Of Vitamin C/Beta-Carotene Co-encapsulation Liposomes

Liposomes have the advantages of good biocompatibility,targeting,non-toxicity and cell affinity,et al.It can be used to encapsulate active ingredients to improve their stability.At the same time,the center and the outer layer of liposome are hydrophilic and the phospholipid bilayer is hydrophobic.So the hydrophilic and hydrophobic active components could be encapsulated simultaneously in the liposome.At present,a large number of studies have been carried out on liposomes encapsulating hydrophilic or hydrophobic liposomes,but few reports have been reported on liposomes encapsulating hydrophilic and hydrophobic liposomes simultaneously.Vitamin C is one kind of water-soluble nutrients and ?-carotene is one kind of fat-soluble active ingredients.In this paper,a co-encapsulation liposome containing vitamin C and ?-carotene in hydrophilic and hydrophobic cavities was prepared by ethanol injection method.And then the physical and chemical properties of the co-encapsulation liposome(L-VC-?C)were determined.The results were as follows:L-VC-?C was prepared by ethanol injection method.Taking the encapsulation efficiency of vitamin C,the encapsulation efficiency of ?-carotene and the particle size distribution of liposomes as the inspection indexes,the effects of the mass ratio of lecithin to cholesterol,the amount of ?-carotene,the amount of vitamin C,and the amount of PBS buffer on the liposomes were investigated.According to the experimental results,the better experimental parameters are selected as follows: The mass ratio of lecithin to cholesterol was 5:1;the amount of ?-carotene was 1.5 mg;the amount of vitamin C was 2 mg;and the amount of PBS buffer was 15 m L.Under these conditions,the encapsulation efficiency of ?-carotene was 98.37±0.41%,the encapsulation efficiency of vitamin C was 82.89±3.14%,and the average liposome particle size was 241.77±10.86 nm.The blank liposomes(un-L),vitamin C-loaded liposome(L-VC),?-carotene-loaded liposomes(L-?C)and L-VC-?C were prepared according to the optimum process parameters.And then the particle size distribution,Zeta-potential,encapsulation efficiency,microstructure,antioxidant properties,storage stability and in vitro simulated gastrointestinal digestion of the liposomes were studied.Transmission electron microscopy images showed that the liposomes were spherical without obvious rupture or adhesion.The results of particle size distribution and zeta-potential showed that there was no significant difference between the polydispersity index and zeta-potential of each liposome sample suspension,and the average particle size of L-VC-?C was larger.The encapsulation efficiency of VC in L-VC-?C was significantly higher than that in L-VC,and the encapsulation efficiency of ?C in L-VC-?C had no significant change compared with that in L-?C.The free radical scavenging rate of L-VC-?C was significantly higher than that of L-?C.Under the storage conditions of 4 °C and 25 °C,there was no significant change in the storage stability of vitamin C,and the storage stability of ?-carotene was significantly improved.In vitro,the release curve of ?-carotene during gastrointestinal digestion was simulated,indicating that liposomes could protect the active substance from damage in the stomach and release it into the small intestine for absorption.The results of kinetic equation fitting showed that the zero order model was applied to understand the release kinetics of ?C from L-?C and L-VC-?C in the stomach,whereas the Korsmeyr-Peppas model was chosen to describe the release of ?C from two types of liposome in small intestine and their release mechanisms were mainly dominated by Fickian diffusion.Using the layer self-assembly technology,the surface of L-VC-?C was modified by chitosan and sodium alginate.And the initial liposome(L),the liposome modified by chitosan monolayer(C-L),and the liposome modified by sodium algate-chitosan double layer(S-C-L)were prepared in order to investigate the physical and chemical properties of liposomes during surface modification.The results showed that the particle sizes of L,C-L and S-C-L increased successively,but the encapsulation efficiency of the active components in each liposome did not change significantly.Zeta-potential and FT-IR showed that chitosan and sodium alginate were modified on the surface of liposome by charge interaction.The results of TGA and DSC showed that the thermal stability of L,C-L and S-C-L were improved successively,indicating that the protective layer formed after surface modification enhanced the thermal stability of liposomes.The results of storage stability showed that surface modification could improve the storage stability of liposomes under the same storage time and temperature.The results of kinetic equation fitting show that the release characteristics of L,C-L and S-C-L conform to the zero-order model.In the digestive stage of small intestine,the release characteristic of ?-carotene in L was in line with the Korsmeyr-Peppas model,while the release characteristics of ?-carotene in C-L and S-C-L were in line with the Higuchi model,and the cumulative release rates of ?-carotene in C-L and S-C-L decreased successively,indicating that the slow-release performance of liposomes was enhanced after surface modification.