Quantification of endocytosis using a folate functionalized silica hollow nanoshell platform

Area of Science:

• Nanotechnology
• Cell Biology
• Biomedical Engineering

Background:

• Assessing cellular uptake and specificity of nanoparticle platforms is crucial for targeted drug delivery.
• Existing methods for quantifying nanoparticle endocytosis can be complex and time-consuming.

Purpose of the Study:

• To develop and validate a quantification method for measuring nanoparticle endocytosis.
• To evaluate the cellular uptake and specificity of folate- and polyethylene glycol (PEG)-functionalized silica nanoshells.
• To assess the potential of folate-functionalized nanoshells for targeted cancer cell delivery.

Main Methods:

• Functionalization of 100-nm hollow silica nanoshells with fluorescein isothiocyanate, folate, or PEG using NHS ester conjugation.
• Characterization of functionalized nanoshells using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
• Quantification of surface folate using UV-Vis spectroscopy.
• In vitro assessment of nanoshell endocytosis in HeLa cancer cells and human foreskin fibroblast (HFF-1) cells using fluorescence and confocal microscopy.
• Development of a fluorescence ratio analysis to quantify endocytosis versus surface adhesion.

Main Results:

• Folate-functionalized nanoshells demonstrated significantly enhanced endocytosis by cancer cells compared to PEG-functionalized nanoshells.
• The fluorescence ratio analysis revealed that 95% of adhered folate-functionalized nanoshells were endocytosed by cancer cells.
• Endocytosis of folate-functionalized nanoshells was cancer cell-selective, sparing normal cells, while PEG-functionalized nanoshells showed lower uptake (27%).

Conclusions:

• A simple and rapid fluorescence ratio analysis method effectively quantifies cellular uptake and endocytosis of nanoparticles.
• Folate-functionalized silica nanoshells exhibit promising targeted uptake and selectivity for cancer cells.
• This method provides a reliable approach for verifying and validating nanoparticle cellular uptake data.