Nonthermal Atmospheric Pressure Plasma Decontamination of Protein-Loaded Biodegradable Nanoparticles for Nervous Tissue Repair

When injected directly into spinal tissue, poly(lactide-co-glycolide) (PLGA) particles have the potential to provide sustained delivery of proteins necessary to promote nerve regeneration. To ensure the injection of sterile particles, a novel decontamination method was developed that can inactivate bacteria while maintaining particle and protein integrity. This method involves the resuspension of protein-loaded particles after preparation in phosphate-buffered saline (PBS) or deionized water that has been subjected to a nonthermal atmospheric pressure discharge. Although different treatment times were required, it was demonstrated that both plasma-treated PBS and water can completely inactivate Escherichia coli when added at a concentration of 103 colony-forming units/mL to PLGA particles with and without protein. Plasma-treated water showed no impact on particle morphology. Plasma treatment of water for 1 minute resulted in the complete sterilization of protein-loaded particles but was able to maintain only 26.6 ± 5.0% of protein activity. On the other hand, plasma-treated PBS required 2 minutes of treatment for complete sterilization of protein-loaded particles but was able to maintain 68.4 ± 10.6% of protein activity. Particles were considered sterile if no bacterial growth was observed after being plated onto bacterial growth agar. The effect of plasma-treated water on release of active protein from particles caused a substantial loss in the initial burst release of protein but did not limit the ability of the particles to provide a sustained release of active protein.