Encapsulation within nanofibers confers stability to the protective antigen protein

The current vaccination paradigm for the prevention of anthrax is insufficient to deal with a potential, widespread epidemic. To solve this issue, we propose a self-administrable vaccine patch capable of delivering the antigen of interest into the skin. This patch is comprised of solid-state nanofibers containing encapsulated protective antigen (PA), a binding protein secreted by Bacillus anthracis. Polyvinylpyrrolidone (PVP) nanofibers, produced by the electrospinning technique, are utilized as our transdermal delivery vector because the high surface area to volume ratio that they afford maximizes contact with the skin; in turn increasing local concentration gradients of reversibly packaged PA when the hygroscopic PVP is solubilized via transepidermal water loss. Previous studies have confirmed the retention of PA immunoreactivity and functionality after the voltage-intensive electrospinning process. The study described here aimed to compare the retention of PA functionality within the nanofibers to PA in solution over a several month period; since it is theorized that encapsulation within nanofibers may confer protein stability. The functionality of encapsulated PA was retained whereas PA in solution was inactive after a 32 week incubation at 4°C; suggesting that encapsulation within nanofibers confers stability to the PA protein.