基于纤维素纳米晶稳定的亚微米Pickering乳液制备

与传统表面活性剂稳定的乳液相比，固体纳米颗粒稳定的Pickering乳液具有较强的界面稳定性、多功能性、低毒性等优势，在生物医药领域具有较大的应用潜力。而相较于尺寸较大的微米级Pickering乳液，亚微米Pickering乳液具有更大的比表面积、更有效的递送效率，有望进一步拓展Pickering乳液在生物医药领域的应用。但由于Pickering乳液的制备影响因素众多，且相互制约，刚性的固体颗粒难以在较小的有限油水界面排布，增加了亚微米Pickering乳液的制备难度。本工作以制备稳定的亚微米Pickering乳液为研究目标，采用具有良好生物相容性的天然多糖–纤维素纳米晶(CNCs)为颗粒乳化剂，角鲨烯作为油相，考察了颗粒浓度、油水比例、水相成分、超声时间及频率对Pickering乳液粒径分布及稳定性的影响，最终得到了具有良好的储存稳定性和抗离心稳定性的粒径为638.7?8.40 nm的亚微米Pickering乳液(CNCs-PE)。通过激光共聚焦显微镜证实了CNCs吸附在油水界面，形成了Pickering乳液结构。利用CCK-8法评价了CNCs和CNCs-PE的细胞毒性，结果表明，两者都具有良好的细胞安全性。此外，将其用于吸附模型抗原OVA，吸附率达到约80%，且肌肉注射部位的切片结果也表明其注射安全性良好。此结果为亚微米Pickering乳液进一步研究提供了参考，并有望拓展CNCs稳定的亚微米Pickering乳液在生物医药领域的应用。

Preparation of submicron Pickering emulsion stabilized by cellulose nanocrystals

Compared with the traditional surfactant-stabilized emulsions, Pickering emulsions stabilized by solid particles have the advantages of strong interfacial stability, versatility, and low toxicity. A number of cases have demonstrated the potential of Pickering emulsions in biomedical applications. Submicron Pickering emulsion has a larger specific surface area and more efficient delivery efficiency than large-sized Pickering emulsions, which is expected to further expand the advantages of Pickering emulsions in the biomedicine fields. However, the size of Pickering emulsions is determined by many factors such as particle properties, characteristics of oil and water phase. And it is difficult to arrange the rigid particles in a limited and small oil–water interface. The above reasons increase the difficulty of preparing the submicron Pickering emulsions. The purpose of this study is to prepare stable submicron-sized Pickering emulsion by utilizing the natural polysaccharide with good biocompatibility-cellulose nanocrystals (CNCs) as particle emulsifier, squalene as oil phase. 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 submicron-sized Pickering emulsion (CNCs-PE) with good storage stability and centrifugal resistance was prepared, and the average size of CNCs-PE was about 638.7?8.40 nm. The confocal laser scanning microscopic (CLSM) images revealed that Pickering emulsion was formed successfully by the adsorption of CNCs on the oil–water interface. The cytotoxicity of CNCs and CNCs stabilized Pickering emulsion (CNCs-PE) was evaluated using CCK-8 method, and it showed that there was no significant loss of cell viability. In addition, the vaccine formulation was prepared by absorbing antigen protein-OVA. The adsorption efficiency of OVA was about 80%, and the histological micrographs of the intramuscular injection site section also showed the injection safety. It is expected to expand the applications of submicron-sized Pickering emulsion based on CNCs in biomedicine fields.