Small Molecules Conjugated Silica Nanoparticles for Dual Targeting of Colon Cancer
Type of DegreePhD Dissertation
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Colorectal cancer is categorized as the third most commonly diagnosed cancer and the second main reason for cancer death in the United States. The conventional treatments of colorectal cancer like surgery, chemotherapy and radiotherapy are hampered by recurrence, off target toxicity and tumor size respectively. Nanoparticles as targeted drug delivery carriers provide an alternative approach for the colon cancer treatment. Nanoparticle surface is modified with targeting ligands which recognize and bind to overexpressed specific biomarkers on cancer cells to deliver chemotherapeutic drug and imaging agent to the cancer cells. However, for efficient cancer targeting, the targeted receptors should be exclusively overexpressed by the cancer cells. Apart from the cell surface receptor, cancer targeting efficiency also depends on the targeting ligand’s density, binding affinity and selectivity towards the targeted receptor. The targeting ligand should have high specificity and binding affinity towards the targeted receptor which will strengthen their interaction. According to literature, another way to increase the cancer cell targeting efficiency is to conjugate dual targeting ligands on the nanoparticle surface. While single targeted nanoparticles target only one type of cancer cell surface receptor, dual targeted nanoparticles simultaneously target two different types of cancer cell surface receptors which enhances targeting. So, the main objective of this project is to study the impact of nanoparticle dual ligand density on targeting of cells with different biomarker expression. In this work, we have developed Silica nanoparticle conjugated with Hyaluronic Acid and Folic Acid to target colon cancer specific CD44 and Folate receptors respectively. We have synthesized the targeted nanoparticles using reverse micro-emulsion method along with EDC-NHS chemistry. The size of the particles characterized by Dynamic Light Scattering were in the range of 150-275nm with moderate dispersity. The morphology of the nanoparticles characterized by Transmission Electron Microscope showed their smooth spherical shape. Results from UV-Vis Spectrophotometer showed that Hyaluronic and Folic Acid conjugation on nanoparticle surface increased with their increasing concentration in the reaction system. The targeted nanoparticles showed >= 70% mammalian cell viability within the concentration and time range tested which proves them to be safe material based on literature. Based on our Flow Cytometry results, we have used SW480 cell line as cell positive for both receptors, WI38 cell line as cell positive for CD44 receptor and Caco2 cell line as cell positive for folate receptor. Throughout the cellular uptake study we observed that increase in FA conjugation didn’t have a significant impact on nanoparticle uptake increase at F:A≤7 and the highest cellular uptake was achieved at F:A=9 for FR positive cells which is the highest examined molar ratio. On the other hand, increase in HA conjugation significantly impacted the nanoparticle uptake. For CD44 positive cells, the cellular uptake increased with increasing HA conjugation but started declining beyond a certain point. So we concluded that the optimum H:A molar ratio for targeted nanoparticles was 0.5-0.75. Since the HA was longer than FA in length, it may have extended itself from the nanoparticle surface and became more accessible to the receptors. Results from the targeting studies demonstrated tremendous potential of the targeted nanoparticles as a promising candidate for theranostic approach.