the study of the colloidal properties of nano liposomes containing beta-carotene produced by thermal method

introduction : the encapsulation of nutraceuticals in lipid based carriers, such as liposomes, can lead to increasing of bio-active ingredients bioavailability and controlled release, maintaining their stability in different environmental conditions and increasing solubility of hydrophobic active ingredients in aqueous conditions. food grade liposomes are being increasingly used in food industry to delivery hydrophilic and hydrophobic components such as vitamin e and vitamin c, ascorbic asid, nutraceuticals, essential omega 3 fatty medium chain fatty acids-vitamine c, nisine, cartenoides, oleic acids, polyphenols include catechine, synamic acids. one of the hydrophobic nutrients with antioxidant and beneficial pro-vitamine property is beta-carotene, which its high hydrophobicity and sensitivity in different environmental conditions has limited using of it for foodstuff enrichment. in order to improve the characteristics of the lipid bilayer, cholesterol traditionally has been included in the lipid membrane. it is important in decreasing permeability and strengthening the membrane. people suffering from hyper-cholesterolaemia are encouraged to avoid foods containing cholesterol. since the plant sterols are natural compounds found in plant cell membranes which help maintain the membrane integrity. such as gama oryzanol is combination of different of plant sterols that is used in the formulation of nanoliposomes in this study to improve the stability of bilayers. the principal aim of this study was to prepare beta-caroten encapsulated nano- liposome formulations as a mean to improve its aqueous dispensability and to study the effect of lecithin-phytosterol concentrations on the partical size, encapsulation efficiency (ee), zeta potential, turbibility of beta carotene loaded nano-liposomes to get the optimized formulation. materials and methods: preparing liposomes is being carried out using different methods one of which is a novel technique called is “mozafari method” (based on heating method). this method is characterized by the absence of organic solvent for the solving of lipids.non-toxicity of produced liposomes; rapid production and scalability are some of the advantages of mozafari method over other methods of liposome production. in this study, the liposomal ingredients were added to a preheated (60 0c, 5 min) water, mixeture of beta-carotene, gamma oryzanol solution and glycerol (final concentration 3% v/v) were added. the mixtures volume increased by adding warm water until 50ml, the mixture was further heated 60 while stirring 1200 rpm for 50-60 min under nitrogen atmosphere. results and discussion: effect of different concentration of lecithin (20, 40, 75, 100, 150, 200 mg) on particle size and zeta potential of nano-liposomes with constant amount of beta carotene (4 mg) and gamma-oryzanol for different concentration of lecithin with ratio 1:14 w/w were evaluated. the particle size of nano liposomes with different concentration of lecithin was obtained below 500nm andthe optimal concentration of lecithin was 100 mg that particle size was minimum (64-88 nm).the gamma-oryzanol is a natural phytostrol which is as stabilizer for liposome membrance and promoting agent of hardness of vesicles wall however, the particle size of liposomes were reduced especially in low concentration of lecithin. the using phytosterols (gamma oryzanol) for maintaining the stability of liposomal membranesystems caused to reducing of particle size from 88nm to 64nm in 200 mg concentration of lecithin. the entrapment efficiency increased by increasing concentration of lecithin for nano-liposomes. it is because increasing the lecithin concentration, more vesicles were produced which in turn increased the loading capacity of nano-liposomes. in the liposome structure, the aqueous core and bilayer are the hydrophilic and hydrophobic parts, respectively. therefore, the phospholipid bilayers place for beta carotene, and other hydrophobic substances. the entrapment efficiency in different concentration of lecithin was between 27-98%. the entrapment efficiency of liposomes containing beta carotene that used gamma oryzanol was less than liposomes without gamma oryzanol probably because the position of capsulation of gamma oryzanol and beta carotene is same in the bilayer of liposome that’s hydrophobic source of liposomes. but gamma oryzanol was not effective on encapsulation efficiency of beta-carotene. the zeta potential, the electric potential in the interface or particle surface charge, is used to predict the stability of colloidal systems. in general, higher zeta potential values, regardless of their positive or negativity, indicate a higher and longer-term stability of the particles. zeta potential of liposomes, which is a measure for the electrostatic repulsion and stability, was -29 and -35 milivolt for samples with and with not containing gamma oryzanol, respectively. for turbidity of liposomes, encapsulation of bioactive compounds can change the optical appearance due to the fact that the refractive index at the interface between solvent and internal phase changes and the size of liposomes may be altered. increasing significantly of turbidity of liposomes (16% -80%), the wave length increase from 0.116 to 0.585 cm-1 high concentration of lecithin maybe due to increasing visuals and hydrophobic interactions.