| Polyelectrolytes have emerged as a versatile, simple and promising tool to deliver therapeutic payloads. Their ability to form complexes with oppositely charged polymers or biomacromolecules has led to various applications in the pharmaceutical and biotechnology industries. In this thesis, three different polyelectrolyte delivery systems have been developed and explored for potential uses in gene and protein delivery.;Polyvinylamine (PVAm) nanogels with different amounts of surface charge and degradability were used to systematically inspect gene transfection efficiency and cytotoxicity. Transfection efficiency of non-degradable nanogels increased with increasing amounts of positive charge. Intriguingly, acid-labile nanogels bearing low charge showed sustained gene transfection and low cytotoxicity. An intricate balance between transfection efficiency and cytotoxicity is crucial for gene vectors. These results led to an exploration of less toxic, small polycations.;Historically, polyplexes using small polycationic peptides such as TAT have shown relatively poor gene transfection, however, previous studies in our group showed that the transfection efficiency could be enhanced by condensing these large polyplexes using calcium. In this thesis, the LABL peptide targeting intercellular cell-adhesion molecule-1 (ICAM-1) was conjugated to TAT peptide using a polyethylene glycol (PEG) spacer. Though the transfection efficiency of TAT polyplexes was reduced by PEGylation, TAT complexes targeting ICAM-1 were able to restore high levels of gene transfection. Thus, targeted TAT polyplexes offer promise for gene delivery to sites of injury or inflammation. Next, other PEGylation strategies using polyelectrolytes were explored.;Repifermin, a truncated version of fibroblast growth factor-10 (FGF-10) also known as keratinocyte growth factor-2 (KGF-2), is a heparin-binding protein with potent regenerative properties. The protein unfolds and aggregates at relatively low temperature (∼37 °C). The thermal stability of several FGFs was enhanced by electrostatic interactions with polyanions. PEG was grafted to the polyanions pentosan polysulfate (PPS) and dextran sulfate (DS). The potential uses of polyanion conjugates were explored using a variety of spectroscopic and calorimetric methods, and dynamic light scattering. PPS-PEG and DS-PEG conjugates were able to stabilize KGF-2 by increasing the melting temperature of the protein complexes. Though there are several parameters that could be optimized to improve the protein structure upon binding, polyanion-PEG conjugates, however, are encouraging reagents that can improve the thermal stability of heparin-binding proteins via electrostatic PEGylation. |
