Cell Phagocytosis Of Surface Functionalized Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles（MSNs）have been extensively investigated in the fields of biosensing,bioimaging and target drug/gene delivery due to their uniform and controllable morphology,high surface area,great chemical stability and excellent biocompatibility.In addition,there are abundant silanol bonds on the surface of MSNs,which could be facilely modified with a series of functional groups or active molecules to improve their performance in biological systems.A deep understanding of the interactions between MSNs and cells,especially the effect of surface modification on cellular uptake efficiency,is of great significance for the investigation of cell endocytosis mechanism and the biological application of different surface functionalized MSNs.However,it is still difficult to determine the accurate cellular uptake efficiency continuously and in real time via a simple and convenient method.In our study,we developed a new approach to evaluate the cellular uptake efficiency of MSNs and PEGylated MSNs semiquantitatively with the help of aggregation induced emission（AIE）-active luminogen（BF₂AVB）and an image processing software ImageJ.the AIE-active luminogen was incorporated into mesoporous silica nanoparticles via a one-pot preparation method to directly synthesize the fluorescent MSNs without surface modification（BF₂AVB-MSNs）and the fluorescent surface PEGylated MSNs（PEG-BF₂AVB-MSNs）.By controlling the synthesis conditions,the particle sizes and emission intensities of the two particles were adjusted to be alike.The sizes,morphologies,structures,compositions and other properties of BF₂AVB-MSNs and PEG-BF₂AVB-MSNs were characterized thoroughly.The prepared BF₂AVB-MSNs and PEG-BF₂AVB-MSNs were incubated with L929cells for a period of time and the fluorescence images of cells were taken by the confocal laser scanning microscope（CLSM）.A serious of fluorescence images of cells could be directly measured and analyzed by an image processing software ImageJ to obtain the fluorescence intensity of a single cell at different time points.Since the concentration and luminescence density of two particles were the same,the cell uptake efficiency at different time periods was consistent with the fluorescence intensity of cells at this time.This report investigated the effect of surface PEGylation on cellular uptake efficiency semiquantitatively and developed a general method to determine the accurate uptake efficiency with the help of AIE material,CLSM and ImageJ.The method not only could contribute to the deeper understanding of the interactions of PEGylated MSNs with cell membranes and also could be further utilized to investigate the cellular uptake of other functionalized MSNs.The results would provide significant information for studying the biological application of multi-functional nanosystems.