UC Davis

The focus of this dissertation research is on the advanced methodology for drug delivery, which includes the synthesis and characterization of drug loaded delivery vehicles. Drug delivery is a rapidly advancing field, ranging from local injections for vaccine delivery to treatment of asthma via pulmonary delivery. There are many illnesses that are left untreated, because of the lack of means to deliver drugs effectively and safely, such as local sustained release to treat post-traumatic osteoarthritis (PTOA) or pulmonary delivery of anti-inflammatory therapeutics for treatment of coronavirus disease 2019 (COVID-19). In this dissertation, I will fill this void, including formulation, characterization, toxicity, and all the way to efficacy. There are three main components in this dissertation investigation. The first, is the development of a greener approach to producing polymer microparticles for local sustained release of flavopiridol. PLGA microparticles represent an important class of materials used for drug delivery. Current synthesis frequently uses conventional emulsion, where dichloromethane(DCM) is used as the organic phase solvent. Due to the health and environmental toxicity of DCM and its slow degradation, this work replaces DCM with a greener solvent, dimethyl carbonate(DMC). To attain narrow distribution of PLGA particle size, microfluidic flow focusing was chosen over conventional emulsion. This new approach successfully produced PLGA microparticles encapsulated with flavopiridol, a kinase inhibitor. These particles exhibit sustained release profile more desirable than the conventional counterparts. The cytotoxicity and activity tests have demonstrated high biocompatibility and efficacy of these PLGA particles. The high sustainability is also evaluated using simple E-Factor(sEF) and complete E-Factor(cEF). The lower health and environmental toxicities of DMC than DCM are evidenced by approximately one order of magnitude higher in lethal dose, i.e., 50%(LD50) values in rat, 5-fold faster degradation rate, and 30% higher GlaxoSmithKline(GSK) combined greenness value. The approach reported in this work shall provide a new and green means for drug delivery in general. The products enable local sustained delivery of flavopiridol for prevention of post-traumatic osteoarthritis, and anti-cancer therapy. The second development is focused on a new approach to quantify drug release kinetics from PLGA microparticles. Current approaches for quantifying drug release profiles from PLGA vehicles involve non-linear fitting using burst, degradation, and diffusion terms. The non-linear fitting is typically performed across the entire time spectrum, assuming that the contribution from each term is constant across the entire release profile. It is known for instance that burst release only occurs during the initial time of release, therefore prior assumption gives poor representation of physical meaning. To improve upon the current approach, a new model was developed by piecewise splitting the fitting terms over two-time regions during release of flavopiridol from PLGA microparticles. The time regions were identified via time dependent SEM imaging, through the analysis of particle morphological evolution during release. The application of our approach to these particles greatly improved and matched the current understanding of release mechanisms. Our approach was validated in larger particles, where new insight was revealed in the evolution of the fitting parameters across time regions. Particles were fabricated with a porous intra-particulate structure, as verified by AFM imaging, to test the genericness of our approach. The intra-particulate structure of these particles was revealed to cause the geometrical changes during release. Our approach further revealed the impact of particle shape change during release in contrast to particle fragmentation, especially through degradation and diffusion mechanisms. This new approach reported in this work, can be applied to drug release from polymer vehicles in general, which allows tunability of release profile to a higher degree. The third development is focused on the production of flavopiridol loaded inhalable ultra-small particles for pulmonary delivery. Treatment of inflammation causing diseases, like COVID-19, generally used an intravenous delivery, however it has been shown that the best course of delivery to the lungs is via inhalation. Production of inhalable particles containing therapeutics are well suited for treatment of lung inflammation and has been demonstrated as the best delivery pathway for pulmonary based diseases. In this work, we showed the development of inhalable particles containing flavopiridol, a CDK-9 inhibitor with demonstrated anti-inflammatory properties, for the first time reported. Formulations of DPPC, L-isoleucine, and flavopiridol were generated into ultra-small particles that presented a desired geometry and size, well suited for pulmonary delivery. The drug loading of the particles was investigated by utilizing UV-Visible spectroscopy, showing 99% efficiency in loading. The presence of DPPC and L-isoleucine were verified by comparing against known standards in ATR-FTIR spectroscopy. The produced particles were demonstrated to be dispersible using a newly developed sampling method for high resolution SEM imaging. The in vitro release of the particles matched the required release kinetics for pulmonary delivery Flavopiridol was found to be biologically active in the produced particles. This work enables the flavopiridol to be delivered to the lungs for treatment of inflammation caused by diseases like pulmonary fibrosis or COVID-19.

This dissertation demonstrates the methodology for drug delivery, through the production and characterization of flavopiridol loaded delivery vehicles for treatment of inflammation in the knee joint capsule via local sustained release or in the lungs via pulmonary delivery, which drives momentum even further into filling the void.