title: Quantification of endocytosis using a folate functionalized silica hollow nanoshell platform.
abstract: A quantification method to measure endocytosis was designed to assess cellular uptake and specificity of a targeting nanoparticle platform. A simple N -hydroxysuccinimide ester conjugation technique to functionalize 100-nm hollow silica nanoshell particles with fluorescent reporter fluorescein isothiocyanate and folate or polyethylene glycol (PEG) was developed. Functionalized nanoshells were characterized using scanning electron microscopy and transmission electron microscopy and the maximum amount of folate functionalized on nanoshell surfaces was quantified with UV-Vis spectroscopy. The extent of endocytosis by HeLa cervical cancer cells and human foreskin fibroblast (HFF-1) cells was investigated in vitro using fluorescence and confocal microscopy. A simple fluorescence ratio analysis was developed to quantify endocytosis versus surface adhesion. Nanoshells functionalized with folate showed enhanced endocytosis by cancer cells when compared to PEG functionalized nanoshells. Fluorescence ratio analyses showed that 95% of folate functionalized silica nanoshells which adhered to cancer cells were endocytosed, while only 27% of PEG functionalized nanoshells adhered to the cell surface and underwent endocytosis when functionalized with 200 and 900  μg , respectively. Additionally, the endocytosis of folate functionalized nanoshells proved to be cancer cell selective while sparing normal cells. The developed fluorescence ratio analysis is a simple and rapid verification/validation method to quantify cellular uptake between datasets by using an internal control for normalization.
authors: University of California, San Diego, Moores Cancer Center, Department of Bioengineering, CalIT2 Nanomedicine Laboratory, La Jolla, California 92093, United States.
authors: Sergio
authors: S
authors: Sandoval
authors: University of California, San Diego, Department of Nanoengineering, Chemical Engineering, and Material Science, La Jolla, California 92093, United States.
authors: Natalie
authors: N
authors: Mendez
authors: University of California, San Diego, Department of Nanoengineering, Chemical Engineering, and Material Science, La Jolla, California 92093, United States.
authors: Jesus G
authors: JG
authors: Alfaro
authors: University of California, San Diego, Department of Nanoengineering, Chemical Engineering, and Material Science, La Jolla, California 92093, United States.
authors: Jian
authors: J
authors: Yang
authors: University of California, San Diego, Department of Chemistry and Biochemistry, La Jolla, California 92093, United States.
authors: Sharraya
authors: S
authors: Aschemeyer
authors: University of California, San Diego, Department of Nanoengineering, Chemical Engineering, and Material Science, La Jolla, California 92093, United States.
authors: Alex
authors: A
authors: Liberman
authors: University of California, San Diego, Department of Chemistry and Biochemistry, La Jolla, California 92093, United States.
authors: William C
authors: WC
authors: Trogler
authors: University of California, San Diego, Department of Chemistry and Biochemistry, La Jolla, California 92093, United States.
authors: Andrew C
authors: AC
authors: Kummel
mesh_terms: D004705:Endocytosis / Q000502:physiology*; D005492:Folic Acid / Q000737:chemistry / Q000493:pharmacokinetics*; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods*; D053769:Nanocapsules / Q000737:chemistry* / Q000648:ultrastructure*; D058608:Nanopores / Q000648:ultrastructure; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D053769:Nanocapsules; D012822:Silicon Dioxide; D005492:Folic Acid