Preparation And Biological Application Of Submicron Pickering Emulsions

Pickering emulsions are special emulsion formulations using solid particles instead of surfactants.The use of solid particles as emulsion stabilizers not only improves the stability of the Pickering emulsions,but also endues Pickering emulsions with many special properties,making Pickering emulsions been used as promising materials for biomedical applications.However,there are still many problems such as poor biocompatibility and the droplet size of Pickering emulsions is in micron,which limit their wide applications in the biomedical field.The purpose of this paper is to prepare a submicron Pickering emulsion with good biocompatibility and preliminarily explore its potential biological applications.The contents of this thesis are as follows:(1)To achieve the goal of preparation of stable submicron Pickering emulsion,the Pickering emulsions were prepared by sonification using squalene as oil phase and screened nanoparticles as emulsifier.The effects of preparation conditions such as particle concentration,oil-water ratio,aqueous phase,ultrasonic time and frequency on size distribution and stability of Pickering emulsions were investigated.Finally,the stable submicron-sized Pickering emulsion with uniform size,good dispersibility and centrifugal resistance was prepared using cellulose nanocrystals(CNCs)as particle emulsifier,and the average size was about 600 nm.And it can be stably stored more than 30 days.The size and Zeta potential of the submicron Pickering emulsion remain basically unchanged under different storage temperatures,such as 4??25? and 37?,which means that the submicron Pickering emulsion with good storage stability.The confocal laser scanning microscopic(CLSM)images revealed that Pickering emulsion was formed successfully by the adsorption of CNCs on the oil-water interface.(2)To initially evaluate the biological application potential of submicron Pickering emulsion as a vaccine adjuvant,the effect and mechanism of CNCs stabilized submicron Pickering emulsion in OVA prophylactic vaccine were investigated by using chicken egg ovalbumin(OVA)as a model antigen.The safety and efficacy of this adjuvant system were evaluated by cell and animal experiments,and then the potential mechanism was further explored.The cellular safety of the submicron Pickering emulsion was demonstrated by cytotoxicity experiments,and the results of muscle tissue section at the injection site and main organ section proved that the submicron Pickering emulsion had good injection safety.In the immunoassay of OVA model antigen,although the submicron Pickering emulsion did not significantly increase the antibody titer level compared with Pickering emulsion groups of which size was about 3 ?m,the secretion of spleen cytokine IFN-? was improved,which means that there was the incline of the Thl-type immune response.In summary,the submicron Pickering emulsion was successfully prepared,and it improved the cellular immunity as a vaccine adjuvant.But its application effect as a vaccine adjuvant remains to be further studied.