This thesis describes the synthesis of water-soluble dendron-conjugated gold nanoparticles (Den-AuNPs) with various average core sizes and the evaluation of stability, cytotoxicity, and cell permeability and uptake of these materials. The characterization of Den-AuNPs using various instruments including transmission electron microscopy (TEM), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), 1H NMR, FT-IR, and UV-vis spectroscopy confirms the dendron conjugation to the glutathione-capped gold nanoparticles (AuNPs). The stability of AuNPs and Den-AuNPs in solutions of different pH and salt concentration was determined by monitoring changes in surface plasmon bands of gold using UV-vis spectroscopy. The Den-AuNPs were found to be more stable than the precursor AuNPs maintaining their solubility at the pHs higher than 4 and with the salt concentrations of up to 100 mM. The improved stability of Den-AuNPs suggests that the post-functionalization of thiol-capped gold nanoparticle surfaces with dondrons can further improve the physiological stability and biocompatibility of gold nanoparticle-based materials. Cytotoxicity studies with AuNPs and Den-AuNPs with and without flourophores were also performed by examining cell viability for 3T3 fibroblasts using a MTT cell proliferation assay. The conjugation of dendrons to the AuNPs with flourophores was able to decrease the cytotoxicity brought about by the flourophores. The successful uptake of Den-AuNPs in mouse fibroblast 3T3 cells shows the physiological viability of the hybrid materials.