علوم و تکنولوژی پلیمر (Jan 2014)
Gamma Oryzanol Bearing Nanoliposome Produced by Modified Thermal Method: Thermal Property, Encapsulation Efficiency, Oscillatory Rheometry
Abstract
Nanoliposomes are one of the most important polar lipid-based nanocarriers which can be used for encapsulation of both hydrophilic and hydrophobic active compounds. In this research, nanoliposomes based on lecithin-polyethylene glycol-gamma oryzanol were prepared by using a modified thermal method. Only one melting peak in DSC curve of gamma oryzanol bearing liposomes was observed which could be attributed to co-crystallization of both compounds. The addition of gamma oryzanol, caused to reduce the melting point of 5% (w/v) lecithin-based liposome from 207°C to 163.2°C. At high level of lecithin, increasing of liposome particle size (storage at 4°C for two months) was more obvious and particle size increased from 61 and 113 to 283 and 384 nanometers, respectively. The encapsulation efficiency of gamma oryzanol increased from 60% to 84.3% with increasing lecithin content. The encapsulation stability of oryzanol in liposome was determined at different concentrations of lecithin 3, 5, 10, 20% (w/v) and different storage times (1, 7, 30 and 60 days). In all concentrations, the encapsulation stability slightly decreased during 30 days storage. The scanning electron microscopy (SEM) images showed relatively spherical to elliptic particles which indicated to low extent of particles coalescence. The oscillatory rheometry showed that the loss modulus of liposomes were higher than storage modulus and more liquid-like behavior than solid-like behavior. The samples storage at 25°C for one month, showed higher viscoelastic parameters than those having been stored at 4°C which were attributed to higher membrane fluidity at 25°C and their final coalescence.Nanoliposomes are one of the most important polar lipid based nanocarriers which can be used for encapsulation of both hydrophilic and hydrophobic active compounds. In this research, nanoliposomes based on lecithin-polyethylene glycol-gamma oryzanol were prepared by using modified thermal method. Only one melting peak in DSC curve of gamma oryzanol bearing liposomes was observed which could be attributed to co-crystallization of both compounds. The adding of gamma oryzanol, caused to reduce the melting point of 5% (W/V) lecithin based liposome from 207 ˚C to 163.2 ˚C. In high level of lecithin, increasing of liposome particle size (storage at 4 ˚C for two months) was more observable and particle size increased from 61 and 113 to 283 and 384 nanometers, respectively. The encapsulation efficiency of gamma oryzanol increased from 60% to 84.3 % with increasing lecithin content. The encapsulation stability of oryzanol in liposome was determined at different concentration of lecithin 3, 5, 10, 20% (W/V) and different storage time (1,7, 30 and 60 days). In all concentration, encapsulation stability slightly decreased during 30 days storage. The scanning electron microscopy (SEM) images showed relatively spherical to elliptic particle which indicating low extent of particles coalescence. The oscillatory rheometry showed that the loss modulus of liposome samples were higher than storage modulus and more liquid like behavior than solid like behavior. The samples storage at 25 ˚C for one month, showed higher viscoelastic parameters than those storage at 4 ˚C which attributed to higher membrane fluidity at 25 ˚C and resulting coalescence.
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