| Vaccine adjuvants are used to increase the immune response in the delivery of subunit antigens. Currently the only FDA approved adjuvants are aluminum based and must be delivered parenterally. Nasal mucoadhesive vaccine administration can decrease cost, increase efficiency and increase patient compliance. The purpose of this study was to develop a mucoadhesive gelatin nanoparticle >500 nm in diameter that can be used to encapsulate a model protein antigen. The particles were prepared by nanoprecipitation of a gelatin solution with acetone. Thiol groups were incubated with gelatin to increase mucoadhesivness at 20, 40, and 80 mg per 1 gram of gelatin. The thiolation chemistry was characterized using UV-Vis and x-ray photoelectron spectroscopy (XPS). The total amount of sulfur present in the gelatin was determined to be 7.48, 30.53, and 46.75 mmol/gram respectively. However XPS analysis revealed that there was no substantial difference between surface sulfur content of the unmodified gelatin nanoparticles and the gelatin nanoparticles modified with 80 mg of iminothiolane. Particle size, charge and morphology were determined using laser light diffraction, atomic force microscopy microscopy and electron microscopy. The average diameter of the unmodified gelatin was 171 nm. The average diameter of the thiolated gelatin nanoparticles was 275 nm. The polydispersity index was approximately 0.61 +/- 0 .04 for all nanoparticles. The zeta (zeta) potential of the unmodified gelatin nanoparticles was -21.5 +/- 2.0 mV and the zeta-potential of the modified gelatin nanoparticles was -25.2 +/- 1.5, -27.3 +/- 0.8, and -28.6 +/- 3.0 mV for the 20, 40, and 80 thiolated gelatin nanoparticles. Particle encapsulation efficiency (EE) and release kinetics were conducted using fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) as a model antigen. The EE of the nanoparticles increased from 35.0% (unmodified gelatin) to 82.5% (highest modified gelatin). Particles encapsulated with FITC-BSA released < 20% of their payload over an 8 hour period at 37°C in phosphate buffered saline before a plateau was reached. To observe in vitro activity, the nanoparticles were incubated with mucus producing human nasal epithelial cells, RPMI 2650, at 37°C for 24 hours. Confocal microscopy revealed that there was no uptake of any of the gelatin nanoparticles by epithelial cells. The unmodified and thiolated gelatin nanoparticles were incubated with human nasal mucus. Mucoadhesiveness was evaluated by measuring the fluorescence of the nanoparticles remaining in the suspension after centrifugation of the mucus solution. There was an 8% decrease in percent nanoparticles remaining but there was no significant decrease in particle remaining due to thiolation. |
