Study Of Antibacterial And Antioxidant Properties For Tannic Acid And Cinnamaldehyde Functionalized Nano-system

Functional food factors are beneficial components in food,which are not only edible,but also have certain medicinal effects,such as anti-cancer,anti-virus,anti-inflammatory,antibacterial,antioxidant and other properties.Tannic acid（TA）,which widely exists in plant roots and fruits,has strong antioxidant activity.Cinnamaldehyde（CA）,derived from cinnamon,is the main component of cinnamon essential oil and has strong antibacterial activity.However,they have poor stability and are easy to decrease or lose their activities under the influence of complex external environment（such as light,temperature,humidity,oxygen,etc.）.Therefore,our research mainly focused on the embedding,protection and delivery of TA and CA,and the development of functionalization nano-technologies for them,so as to improve their stabilities and bio-availabilities.At the same time,the selected nano-systems with excellent performances were further applied to fruit preservation and in vivo antibacterial infection,and were applied to functional modification of hydrogels,aiming at providing new ideas for the research and application of nanomaterials of TA and CA,as well as the development and application of green multifunctional hydrogels.First,a three-phase functional nano-system of polysaccharide-polyphenol-protein was successfully constructed,namely chitosan-tannic acid-lysozyme nanoparticles（CS-TA-L NPs）.Using chitosan as wall material,TA was loaded into CS-TA-L NPs with core-shell structure,which was realized by ion crosslinking and ultrasonic assisted method.The results showed that the introduction of lysozyme（L）was helpful to form the core-shell structure of this nano-system,which proved that the introduction of protein component was useful for the loading of polyphenols in the polysaccharide system.In addition,this simple and effective three-phase nano-system protected the biological activity of TA,made CS TA L NPs have good antioxidant and antibacterial properties,and provided a new approach for the construction of delivery nano-system for functional food factors.Next,cinnamaldehyde（CA）was loaded in a nano-system based on copper-gallic acid-cinnamaldehyde-polydopamine nanorods（Cu-GA-CA-PDA NRs）with slow release of CA.Firstly,copper-gallic acid nanosheets（Cu-GA NSs）were prepared by the ion chelation between copper ions(Cu²⁺)and gallic acid（GA）.Then,using Cu-GA NSs as a stabilizer,copper-gallic acid-cinnamaldehyde nanosheets（Cu-GA-CA NSs）was fabricated.Further,based on the self-polymerization characteristic of dopamine and ultrasonic assisted stripping strategy,Cu-GA-CA-PDA NRs were successfully prepared.The results showed that NIR 808can trigger Cu-GA-CA-PDA NRs to generate heat and release CA,exhibiting excellent antibacterial property.Results of antioxidant test showed that Cu-GA-CA-PDA NRs had excellent free radical scavenging activity.In addition,fruit preservation test proved that Cu-GA-CA-PDA NRs can effectively inhibit the reproduction of microorganisms on the surface of cherry tomatoes and small oranges,showing a good preservation effect.Results of in vivo antibacterial infection test revealed that NIR-mediated Cu-GA-CA-PDA NRs could effectively accelerate the healing of Staphylococcus aureus-infected wounds.Therefore,this study provided a competitive strategy for the development of multifunctional cinnamaldehyde-loaded nano-systems.In order to construct a simplify and green strategy for co-delivering tannic acid and cinnamaldehyde nanosystem,an ultrasound triggered irreversible self-assembly and ion crosslinking co-driven strategy was proposed for the first time to prepare multifunctional cinnamaldehyde-tannic acid-zinc acetate nanospheres（CA-TA-ZA NSs）and realize the fusion of hydrophilic and hydrophobic molecules.This strategy was based on the self-assembly and self-emulsification properties between cinnamaldehyde（CA）and tannic acid（TA）,as well as the ionic cross-linking interaction between TA and zinc acetate（ZA）.The optimization experiment showed that when the mass ratio of CA/TA is 4:1,the CA-TA self-assembled nano-emulsions（CA-TA NEs）had the smallest particle size and good dispersibility.When the addition amount of ZA was 0.4 mmol,the ionic crosslinking of TA and ZA reached equilibrium.In CA-TA-ZA NSs,the encapsulating efficiencies of CA and TA were 90.36±0.91%and91.92±0.04%,respectively.In addition,CA-TA-ZA NSs had good thermal stability and sustained-release characteristics.The successful loading of CA and TA made CA-TA-ZA NSs have excellent antibacterial activity against Staphylococcus aureus and Escherichia coli.Results of antioxidant test showed that CA-TA-ZA NSs could effectively scavenge ABTS⁺,DPPH^·and·OH free radicals,revealing their great potential to reduce oxidative stress damage.Through the coating preservation technology,we found that CA-TA-ZA NSs can effectively inhibit the growth of microorganisms on the surface of strawberry and maintain its freshness,which provided a possibility for the application of CA-TA-ZA NSs in the field of food preservation.Therefore,this study provided a new approach for the construction of multifunctional nano-systems co-loaded with TA and CA.Further,in order to explore the application of CA-TA-ZA NSs in the field of anti-bacterial infection,a model of Staphylococcus aureus-infected wounds was constructed,and the multifunctional CA-TA-ZA NSs prepared in the previous chapter was used in the in vivo antibacterial infection test.First,using ZA as a crosslinking agent,CA-TA-ZA NSs were successfully loaded into the chitosan matrix with 3D network structure,and a new type of"all-in-one"chitosan hydrogel was designed.The hydrogel had excellent antibacterial,antioxidant,anti-inflammatory and reducing oxidative stress damage abilities.In addition,CA-TA-ZA NSs functionalized hydrogels can achieve in situ and rapid gelation at wound sites,completely cover the irregular wounds,and effectively kill bacteria,clean wound microenvironment,restore the body’s immune system to normal physiological activities,promote vascular repair and hair follicle regeneration,induce skin tissue remodeling,thereby accelerating the healing of bacterial-infected wounds.In conclusion,this study had achieved a balance between functional properties,biodegradability,safety and tissue regeneration properties of hydrogels,providing a new direction for the application of TA and CA nano-system,and providing a new strategy for the design of advanced functional materials modified by functional food factors.