Feilin Lin,Xinyu Zhao,Shujuan Yang,Furui He,Wenqi Qin,Houkui Gong,Gaobo Yu,Yuhong Feng,Jiacheng Li
Pickering emulsions stabilized by soft particles have attracted increasing interest in research areas including food , pharmaceutics, and drug delivery. The interface-film properties have a great influence on the stability of Pickering emulsion. However, in situ studies of the stability of Pickering emulsions by direct visualization technology have not been well explored. In this work, a kind of amphiphilic alginate-based fluorescent polymer was synthesized (named Alg-TPVA) by Ugi reaction. The Alg-TPVA which can self-assemble into micellar aggregates in aqueous solution and was used to stabilize Pickering emulsion. The addition of Ca 2+ triggered the gelation of Alg-TPVA aggregates and changed the properties of the oil-water interface. The size and morphology of the Pickering emulsion were studied in detail by optical scattering and microscopy analyses. The viscoelasticity of the interface-film was characterized by rheological test. The interface-film was further characterized in situ by confocal laser scanning microscope. The spatial network structure of the interface was observed by scanning electron microscope. Results showed that the Alg-TPVA aggregates can adsorb on the oil-water interface to form an interface-film that stabilizes the emulsion. When Ca 2+ is 0.04 M, the interfacial viscoelasticity increases to the maximum, and the thickest interface-film formed rendered the best stability of Pickering emulsion. Moreover, the fluorescence-visualization technology can play a significant role in understanding emulsion stability.
The emulsion gels transformed by Pickering emulsions have great potential as a novel platform for oral drug delivery. In this study, an innovative alginate-based fluorescent colloidal particle was synthesized by Ugi reaction with alginate and carbon dots , which can stabilize Pickering emulsion at the present of Ca 2+ . The Pickering emulsions were converted to emulsion gels during gastric digestion. The microstructure of interfacial film was characterized in situ with confocal laser scanning microscopy. In the process of simulated gastrointestinal digestion, phase conversion of the Pickering emulsion was observed directly in situ by an automatic living cell imaging system. The results showed that clear fluorescent interfacial films can be visualized after simulated oral digestion, and fluorescent spheres were appeared after gastrointestinal digestion, indicating that Pickering emulsions were transformed into emulsion gels. Moreover, results on cell viability and cell uptake showed that the Pickering emulsion had good biocompatibility, which could be taken up by Caco-2 cells and could sustain the release of the drug. The formation of emulsion gels delays the digestion rate and improves the stability of encapsulated curcumin (CUR). In particular, in situ visualization technique also has promising applications in the digestion process and cellular uptake.
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