This article reports the development of a multifunctional silica nanoparticle system for targeted delivery of hydrophobic imaging and therapeutic agents. Normally, silica nanoparticles have been widely used to deliver hydrophilic drugs such as doxorubicin while difficult to carry hydrophobic drugs. A strategy for loading hydrophobic drugs onto silica nanoparticles via covalent attachment was developed in this study as a universal strategy to solve this problem. Docetaxel, one of the most potent therapeutics for cancer treatment is selected as a model hydrophobic drug and quantum dots (QDs) are used as a model imaging agent. Such a multifunctional delivery system possesses high drug loading capacity, controlled drug release behavior and stable drug reservation. A mixed layer of polyethylene glycol conjugated phospholipids is formed on the nanoparticle surface to further enhance the biocompatibility and cell fusion capability of the delivery system. Folic acid as ligand is then conjugated onto the surface layer for targeting. Such a multifunctional system for targeting, imaging and therapy is characterized and evaluated in vitro. Fluorescent confocal microscopy is used to monitor the cellular uptake by specific cancer cells. Cytotoxicity studies are conducted by using MTT assay.
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