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This dissertation describes a microfluidic technique for the synthesis and preparation of tumor-targeted liposomes for drug delivery applications plus the utilization of these liposomes for innovative pharmaceutical and preclinical research applications. Microfluidic hydrodynamic flow focusing enables the production of nearly monodisperse populations of nanoscale liposomes while providing exquisite control over size in comparison to traditional bulk-fluid liposome synthesis methods. Here, the microfluidic process was first implemented using lipids functionalized with high molecular weight polymers and other molecules to determine the ability to prepare long-circulating, tumor-targeted liposomes. Additionally, the process was realized in thermoplastic microchannels which require simpler, less expensive fabrication methods than the silicon-based devices in which this technique was originally demonstrated. Second, additional functionalities were integrated into the microfluidic platform, including buffer exchange and remote drug loading in-line with liposome synthesis, to yield a continuous process for microfluidic preparation of liposomes containing high concentrations of amphipathic drugs which are commonly used for the treatment of cancer and other diseases. Next, the microfluidic technique, which is typically performed in two-dimensional rectangular microchannels, was implemented within a three-dimensional concentric capillary structure to assess the impact of edge effects during flow focusing on liposome synthesis in the two-dimensional system and to demonstrate a higher-throughput method for microfluidic liposome preparation. Along with exploring these additions to and variations upon the established microfluidic platform, microfluidic-enabled populations of liposomes were used for innovative pharmaceutical and preclinical research to demonstrate their utility in practical applications. First, nanoscale liposomes with discrete diameters were produced in order to investigate the effect of liposome size on cellular uptake mechanisms in vitro for a human epithelial colorectal adenocarcinoma (Caco-2) cell line. Next, liposomes with diameters below a proposed size cutoff for transdermal delivery (~40 nm) were produced to examine their ability to passively traverse layers of ex vivo porcine skin. The original research presented in this dissertation demonstrates the capacity to incorporate additional on-line liposome preparation functionalities into an established microfluidic technique, advances the platform to render it more amendable for widespread use, and highlights the advantages of microfluidic-prepared liposomes for practical applications through pharmaceutical and preclinical research.