| Nerve regeneration following spinal injury remains one of the most difficult to solve medical problems mainly because the spinal tissue environment is not conducive to nerve growth. PLGA nanoparticles offer great potential as a sustained delivery system for proteins that promote nerve regeneration. However, in order for PLGA-particle protein delivery in injured spinal tissue to be clinically relevant, various drawbacks including: low encapsulation efficiency, protein instability, incomplete protein release and particle biocompatibility have to be addressed and overcome.;This research focuses on developing the water/oil/water (W/O/W) double emulsion procedure to physically entrap protein within PLGA particles and systematically analyzing the effects on particle morphology, protein loading, protein activity and sustained active protein release. Variables evaluated include solvent miscibility, energy input, PLGA concentration, and various additives. Adjustments to formulation parameters had significant advantages on size distribution, loading efficiency, protein stability, and increased active protein released. Most particles demonstrated sustained release of active protein over 60 days and a mathematical model was developed to illustrate a tri-phasic release profile.;Because of direct injection into spinal tissue, biocompatibility concerns are directly related to particle sterility, surface characteristics and cytotoxicity. A plasma sterilization method was developed that can completely inactivate an E. coli bacteria load of 103 CFU/ml while maintaining particle integrity and protein stability. Surface characteristics were modified by altering the preparation conditions to eliminate residual surfactant. Other surface modification methods included ways to increase surface hydrophilicity and these methods involved both PEGylation and plasma treatment. All modification methods resulted in no measurable amount of protein (IgG) adsorbed to the particle surface. Fabrication methods were modified to eliminate particle cytotoxicity. Plasma treatment showed no cytotoxic effects, while mPEG-PLGA showed minimum cytotoxicity. PLGA particle degradation showed no impact on cytotoxicity.;Overall, this research advanced the clinical relevance of a PLGA protein delivery system for a multitude of applications. The drawbacks preventing such a delivery system from in vivo use were addressed. |
