| Popis: |
Therapeutic proteins and other biologics are becoming increasingly common across wide swathes of the healthcare system. However, biological macromolecules are particularly susceptible to immune recognition, systemic clearance, and degradation. Various methods of evading the immune system and prolonging the bioavailability of a given therapeutic have been devised and implemented. Polyion complexation, whereby a block ionomer is complexed with a polyelectrolyte to form a core-shell structure, has become an increasingly popular method of encapsulation. Notably, the most common shell forming block is poly(ethylene glycol) (PEG). Understanding the complexity of polyion complex systems requires background knowledge of how complexation is driven. Chapter 1 of this dissertation reviews polymer complexation, encapsulation of proteins, PEG characteristics and alternative options, and the biology around brain derived neurotrophic factor (BDNF).Chapter 2 of this dissertation addresses the nanoformulation of BDNF and PEG-b-poly(glutamic acid) to yield a polyion complex nanoparticle, termed Nano-BDNF. Extensive characterization indicates a spherical, core-shell particle with size and dispersity appropriate for administration. Association is driven by electrostatic attraction between the polymer and protein, then stabilized via a hydrogen bonding network. The particle is stable in high ionic strength solutions, protects from common mucosal opsonins, and selectively releases to specific binding partners. Encapsulation preserves activity in the brain and mediates delivery via the intranasal to brain pathway. Also, treatment in a Parkinson’s disease model is efficacious. However, the particle was formulated with a polymer containing PEG. There are several issues with PEG, (reviewed in Chapter 1), primarily immunogenicity. Chapter 3 deals with the reformulation of Nano-BDNF with two novel polymers. Reformulation yielded relatively small and narrowly dispersed particles which have similar morphology and behavior to the original Nano-BDNF formulation. Additionally, we confirm cooperative binding and investigate the effects of pH change on formation. Indeed, we observe behavior consistent with the polyelectrolyte complexes which inspired the development of polyion complexes. This reformulation can offer a way to diversify and supplement the therapeutic arsenal in order to avoid disruptions by immunogenic PEG. |
