Study On The Preparation And Stability Of Cinnamaldehyde Liposomes

Cinnamaldehyde is a hydrophobic active ingredient of plant essential oil with its unique functionality and aroma keeping effect.However,cinnamaldehyde has a poor solubility in water and is susceptible to oxidized in air,so the application is subject to great restrictions.The encapsulation of cinnamaldehyde by liposomes is one of the most effective ways to solve these problems,which can not only improve the water dispersion of cinnamaldehyde,but also avoid contact with the external environment.In this paper,cinnamaldehyde was encapsulated with mixed lipids as wall materials,and the preparation technology was optimized.On this basis,the effects of temperature,pH,ionic type and ionic strength on the stability of cinnamaldehyde liposomes were investigated.The stability of cinnamaldehyde liposomes at high ionic strength was improved by the modification of sodium carboxymethyl cellulose(CMCNa).With the encapsulation efficiency as the index,the determination of free content of cinnamaldehyde in liposomes was established by using organic solvent extraction method.The results showed that,the extraction efficiency of the free cinnamaldehyde was the best when the extraction time was 3 min and the extraction was repeated twice with petroleum ether as the extraction solvent.The recovery rate of free cinnamaldehyde in liposomes was 90.86% with better reproducibility.The effects of preparation conditions on the encapsulation of cinnamaldehyde liposomes were investigated by single factor test.The parameters were optimized as follows: the ultrasonic power was 240 W,the ultrasonic time was 2 min,the weight ratio of phospholipid/Tween80/cinnamaldehyde was 1: 0.2: 0.12,and the wall concentration was 3%(w/w).Under these conditions,the average particle size of cinnamaldehyde liposomes was 67.76 nm,the encapsulation efficiency was 53.66%,and the retention rate was 80.85% after heating at 45°C for 6 h.With the help of exogenous fluorescent probe and Raman spectroscopy,the effect of the ratio of core to wall on the bilayer structure of liposomes was explored.It was found that an appropriate increase in the ratio of core to wall could enhance the microviscosity and horizontal order parameters of liposomal bilayer,so as to improve the thermal stability.Based on the analysis of changes of the average particle size and the retention rate,the effects of temperature,p H,ionic type and ionic strength on the stability of cinnamaldehyde liposomes were investigated.The results showed that the retention rate of cinnamaldehyde decreased rapidly when the pH was too low or too high,and the alkaline environment was more obvious than the acid.After heating at 37 °C for 24 h,the Na3C6H5O7 ionic solution had significant effect on the liposomes.The average particle size increased to 92 nm with 31% of the change rate and the retention rate decreased to 75%.The average particle size of liposomes increased gradually and the retention rate decreased rapidly when the ionic strength was above 0.22 mol/L.When the ionic strength solution was used as the hydration medium,the encapsulation efficiency decreased and the average particle size increased with the increase of ionic strength.When the ionic strength was higher than 0.66 mol/L,the atomic force microscopy images showed that the liposomes had obvious aggregation and fusion phenomenon.With the encapsulation efficiency,the average particle size and the retention rate as indexes,the effects of anionic polysaccharide modification on the properties of cinnamaldehyde liposomes were investigated.The results showed that the encapsulation efficiency decreased and the average particle size increased with modification of polysaccharide.While the appropriate concentration of CMCNa modification combined with ultrasonic treatment had the least effect on the encapsulation efficiency and the average particle size of liposomes and the retention rate showed the slowest rate of decline.Based on the comparison of the appearance,the particle size,the encapsulation efficiency and rheological properties of liposomes,the effects of the molecular structure and concentration of CMCNa on liposome physical stability were investigated with high ionic strength solution as hydration medium.The results showed that the relative molecular weight and concentration of CMCNa were positively relative to the improvement of the aggregation of liposome particles.The improvement effect of CMCNa on the colloid stability of liposomes was the most obvious when the relative molecular weight of CMCNa was 1185955,the degree of substitution was 0.90 and the concentration was 0.8%(w/v).