Chronic pulmonary disorders, marked by excessive extracellular matrix deposition (ECM) or fibrosis, are the most resistant to present clinical therapies resulting in prognoses of 50% life expectancy three years from diagnosis. Inadequacies of current treatments may be attributable to limitations in non-invasive therapeutic administration modalities. However, with the use of polyketal microparticles (PKMs), a novel drug delivery vehicle, a myriad of therapeutic schemes may be explored. Polyketals are a new polymeric family characterized by tissue biocompatibility, rapid hydrolysis, and benign degradation byproducts making it attuned for pulmonary applications. Potential treatments such as siRNA, oligo nucleotides, enzymes and other biomolecules can be encapsulated within PKMs and administered non-invasively via inhalation. For this study, we selected a model therapeutic peptide, Ac-SDKP, with established anti-fibrotic properties as the load for PKMs. For lung dysfunctions accompanied by fibrotic scarring, Ac-SDKP possesses promise in restoring the normal ECM framework. To assess PKMs viability as a pulmonary drug delivery vehicle three objectives were initially defined: 1) Synthesize particles possessing aerodynamic properties conducive for aerosolization 2) Optimization of the therapeutic load, Ac-SDKP, in PKMs to levels that will translate to clinical dosing concentrations, and 3) Determine the biocompatibility of the PKMs in the lung. Optimization of the Ac-SKDP loading within PKMs and size analysis revealed that a solid in oil in water double emulsion particle synthesis technique produced the most ideal microspheres. Based on previous reports, the loading efficiency attained, when locally dispensed, should reach clinical dosing requirements. Synthesized particles were compatible with aerosolization criteria; i.e., diameters below 3 μm and low polydispersities. In addition, we evaluated PKM tissue biocompatibility using a murine lung model. Examination of bronchoalveolar lavage fluid demonstrated only a slight inflammatory response to intratracheal particle injections of PKMs whereas PLGA, a commonly used biomaterial, elicited a significantly higher response. Histological assessment of the lungs following particle injection verified PKMs biocompatibility superiority. In conclusion, small-diameter PKMs are a suitable delivery system for pulmonary drug delivery, capable of delivering small peptide therapeutics and evading the local inflammatory response. The present work will enable expansion of therapeutic avenues capable of combating chronic lung disease.

Acute liver failure is a major cause of death in the world, and effective treatments are greatly needed. Liver macrophages (Kupffer cells) play a major role in the pathology of acute liver failure, and drug delivery vehicles that can target therapeutics to Kupffer cells have great therapeutic potential for treating acute liver failure. Microparticles, formulated from biodegradable polymers, are advantageous for treating acute liver failure because they can passively target therapeutics to Kupffer cells. However, existing biomaterials are not suitable for the treatment of acute liver failure because of their slow hydrolysis and acidic degradation products. In this dissertation, I present the development of a new class of biodegradable materials, termed aliphatic polyketals, which have considerable potential as drug delivery vehicles for the treatment of acute liver failure because of their neutral degradation products and tunable hydrolysis kinetics. The anti-inflammatory enzyme, superoxide dismutase (SOD), was delivered using polyketal microparticles to the liver for treating acute liver Failure. Our results demonstrated that polyketal microparticles significantly improved the efficacy of SOD in treating LPS-induced acute liver damage in vivo, as evidenced by decreased levels of serum alanine transaminase, which corresponds to the extent of damage in the liver, and serum level of tumor necrosis factor-alpha, which corresponds to the secretion of pro-inflammatory cytokines. The completion of this thesis research demonstrates the ability of polyketal-based drug delivery systems for treating acute inflammatory diseases and creates a potential therapy for enhancing the treatment of acute liver failure.

Amyotrophic lateral sclerosis (ALS) is a devastating disease. Currently, there is no cure for this disease, and effective treatment strategies are greatly needed. Calpain activation plays a major role in the motor neuron degeneration that causes ALS. Therefore, therapeutic strategies can inhibit calpain activity in the central nervous system (CNS) have great clinical potential. The calpain inhibitors AK295 and MDL-28170 have been demonstrated to be neuroprotective in animal models of neurological injury, and should have great potential to treat ALS; however delivery problems have hindered their clinical success. Therefore, development of a new strategy that can locally deliver the calpain inhibitors to the central nervous system could significantly improve the treatment of ALS. The objectives of my thesis research were (1) to develop high molecular weight polyketals that provide sustained release properties for hydrophobic molecules, (2) to formulate calpain inhibitor-encapsulated polyketal microparticles which have a release half life of one month in vitro, (3) and to evaluate the performance of polyketal microparticles for delivering calpain inhibitors to the spinal cord in vivo. In completing these specific aims, we have developed biodegradable polymeric microparticles for the delivery of calpain inhibitors, AK295 and MDL-28170 to treat ALS. The results of calpain assays showed that both AK-PKMs and MDL-PKMs maintained most of their inhibitory activities even after the robust emulsion process. The in vitro release profile of MDL-28170 in MDL-PKMs showed that 50 % of the drug was released in the first 30 days. Experiments using dye-encapsulated microparticles showed that polyketal microparticles (1-2 ìm) are not easily cleared in the neutral physiological environment and can have potential to continuously release drug from the injection sites in the spinal cord. The efficacy of calpain inhibitor-encapsulated PKMs were studied by evaluation the behavior and survival of SOD1G93A rats, a genetic rat model for ALS. We observed the trend toward improvements in grip strength and rotarod performance in the first two months from the AK-PKMs treated group, however, further improvements are needed to enhance their in vivo efficacy.