Study On The Preparation And Antibacterial Activity Of Cinnamaldehyde Liposomes And Their Chitosan Modifiers

Cinnamaldehyde is an active component of plant essential oil,with broad-spectrum antimicrobial activity.However,cinnamaldehyde has strong volatility,unstability and poor solubility,which limits its application.Liposomes as carriers can be an effective way to solve these problems.The entrapment system can improve the stability of the core material,but at the same time,it may also weaken the antibacterial activity of the core material.In this paper,the effects of particle size and core-wall ratio on the stability and antibacterial activity of cinnamaldehyde liposomes during storage were studied.Besides,the stability and antibacterial activity of cinnamaldehyde liposomes were improved by chitosan modification.On the basis of these,the antibacterial mechanism of cinnamaldehyde liposomes modified by chitosan was preliminarily investigated.Based on the analysis of the retention rate and the change of particle size distribution,the effects of average particle size and core-wall ratio on the storage stability of liposomes were studied.The results showed that the liposome stability decreased with the increase of average particle size.The retention rate of cinnamaldehyde was 64% after the storage of liposome with an average particle size less than 100 nm at 37℃ for 20 d.Meanwhile,the particle size distribution was more uniform,and the polydispersity index(PDI)was 0.290.The samples with larger core-wall ratio were more easily aggregated during storage.Nevertheless,the change of retention rate was opposite.After being kept at 37℃ for 30 d,the retention rate of liposomes with a core-wall ratio of 3:10 was the highest,which was 56%.Taking Escherichia coli and Staphylococcus aureus as the model system,the influence of average particle size and core-wall ratio on the bacteriostatic properties of liposomes was investigated,with the bacteriostasis efficiency and killing log value as evaluation indexes.The results revealed that the particle size in range of 100~600 nm had no significant effect on the antibacterial ability of cinnamaldehyde liposomes during initial storage,but their killing log value was significantly lower than that of unencapsulated cinnamicaldehyde.After being placed at 37℃,cinnamaldehyde liposomes showed increased inhibition rate.With the rise of the corewall ratio,the antibacterial activity of cinnamicaldehyde liposomes increased.Staphylococcus aureus treated by the liposome with a core-wall ratio of 3:10 after 30 d storage for 8 h showed almost no growth,and Escherichia coli which was treated for 12 h hardly grew up.The effects of chitosan concentration on the properties of cinnamaldehyde liposomes were studied with the encapsulation efficiency,average particle size,retention rate and bacteriostasis efficiency as evaluation indexes.The results showed that with the increase of concentration,the encapsulation efficiency and average particle size of cinnamaldehyde liposomes modified by chitosan increased.When the chitosan concentration was 4 mg/m L,the encapsulation efficiency of liposomes was 53%,which was 31% higher than that of unmodified liposomes.After the storage of 28 d,chitosan could efficiently prevent cinnamaldehyde from leaking from liposomes,and the retention rate of cinnamaldehyde was 50%.Taking Escherichia coli as the research object,it was found that chitosan concentration had no significant effect on the antibacterial activity of cinnamaldehyde liposomes,but for Staphylococcus aureus,the inhibitory ability of liposomes increased with the increase of chitosan concentration.The antimicrobial mechanism of cinnamaldehyde liposomes modified by chitosan was analyzed by investigating the membrane integrity,membrane potential and extracellular protein content.The results showed that chitosan and cinnamaldehyde could destroy the integrity of cell membrane and lead to the leakage of protein from microbiological cells.Compared with the cinnamaldehyde liposomes,cinnamaldehyde liposomes modified by chitosan had stronger antibacterial ability.The membrane potential of Escherichia coli and Staphylococcus aureus which were treated for 3 h decreased by 39% and 94%,respectively.The effects of different antibacterial agents on the quality of meat products were studied with pH value,total volatile base nitrogen,total plate count and sensory evaluation of spiced meat as indexes.The results showed that cinnamaldehyde liposomes modified by chitosan could efficiently control the growth of microorganisms in spiced meat when compared with cinnamaldehyde liposomes,but its overall acceptability was relatively poor.