Nanoparticles for Cancer Detection and Therapy: Towards Diagnostic Applications of Quantum Dots and Rational Design of Drug Delivery Vehicles

This thesis describes observations, techniques and strategies, which contribute towards the development of nanoparticle based detection and treatment of cancer. Quantum dots and biorecognition molecules were studied towards applications in detection and microgels were used in the rational design of a targeted drug delivery vehicle. The fluorescence intensity of quantum dots was examined in buffers commonly used in molecular biology. The fluorescence intensity of ZnS-capped CdSe quantum dots (QDs) was found to vary significantly, depending on the amount of ZnS capping on the QDs or the concentration, pH and type of buffer the QDs were in. Since fluorescence cannot reliably be used to quantify QDs, an alternative quantification method was developed, which does not rely on their fluorescence. This method employs phage display to identify nanoparticle-specific bacteriophage which were then applied in an assay to quantify QDs in environments where absorbance or fluorescence spectroscopy are ineffective. Biorecognition molecules, which can direct nanoparticles to a molecular target, were also identified through phage display. Phage display on whole cells was used to identify a peptide, which was conjugated with QDs to stain HeLa (cervical cancer) cells. A high-throughput phage display screening strategy was also developed, which could enable the simultaneous identification of multiple biorecognition molecules from a single library. QD-encoded microbead barcodes were conjugated to protein targets and then used to screen a phage display library. The beads and the binding phage were then separated using flow cytometry and fluorescence assisted cell sorting. Finally, biorecognition molecules were combined with nanoparticles to create drug delivery vehicles, which were designed to protect, deliver and then release chemotherapeutic drugs through an intracellular pH trigger. PolyNIPAAm and chitosan hydrogels, under 200 nm in diameter, were loaded with chemotherapeutic drugs, conjugated to transferrin and tested in vitro on HeLa cells. These projects demonstrate the great potential in this growing field as well as some of the many challenges that have yet to be overcome.