The therapy suppressive tumour microenvironment (TME) continues to hinder anti-cancer therapies. Local delivery of therapeutic proteins, including potentially toxic factors, is increasingly needed to enhance immunotherapeutic bioactivities and minimize systemic toxicity. To this end, we are developing vehicles that immobilize to extracellular matrix (ECM) components upregulated in TME for localization of polymer-grafted bioactive cytokines with tunable degradation rates to control cytokine clearance. The grafted cytokine would be bioactive, and the length of the therapy would be governed by the degradation kinetics of the hydrolytic linker between the cytokine and polymer. The cytokines were expressed and purified, and their biological activity was confirmed. Click chemistry was used to graft the therapeutic proteins and collagen-binding peptides to the copolymer. Production of the therapeutic carriers was confirmed by SEC and fluorescent measurements. Biolayer interferometry and tracking immobilization inside collagen gel confirmed the binding affinity between carriers and collagen type 1. In vitro studies confirmed the bioactivity of the carriers in the presence of T-cells and macrophages. In summary, ECM binding vehicles for local sustained protein release will aid in the local delivery of therapeutic proteins to alter TME and promote immunotherapies. Screens will be conducted in multicellular spheroid models to identify bioactive formulations. / Thesis / Master of Science (MSc)

Mass spectrometry has enjoyed enormous popularity over the years for studying biological systems. The theme of this dissertation was to develop and use mass spectrometry based tools to solve five biologically oriented problems associated with protein architecture and extend the utility of these tools to study protein polymer conjugation. The first problem involved elucidating the false negatives of how proteins with few basic residues, forms highly charged ions in electrospray ionization mass spectrometry (ESI MS). This study showed that the unfolding of polypeptide chains in solution leads to the emergence of highly charged protein ions in ESI MS mass spectra, even if the polypeptide chains lack a sufficient number of basic sites. In the second problem, a new technique was developed that can monitor small-scale conformational transitions that triggers protein activity and inactivity using porcine pepsin as a model protein. This work allowed us to revise a commonly accepted scenario of pepsin inactivation and denaturation. The physiological relevance of an enzyme-substrate complex was probed in our third problem. We observed by ESI MS that pepsin forms a facile complex with a substrate protein, N-lobe transferrin under mildly acidic pH. The observed complex could either be a true enzyme-substrate complex or may likely results from an electrostatically driven association. Our investigation suggested that the enzyme binds nonspecifically to substrate proteins under mild acidic pH conditions. The fourth problem dealt with the investigation of conformational heterogeneity of natively unstructured proteins using a combination of spectroscopic techniques and ESI MS as tools. It was observed that four different conformations of alpha-synuclein coexist in equilibrium. One of these conformations appeared to be tightly folded. Conclusions regarding the nature of these states were made by correlating the abundance evolution of the conformers as a function of pH with earlier spectroscopic measurements. The final problem was aimed at monitoring conformational transitions in polypeptide and polymer segments of PEGylated proteins using PEGylated ubiquitin as a model system. This studies suggested that for a PEGylated protein, polypeptides maintain their folded conformation to a greater extent whiles the polymer segments are bound freely to the protein.