High molecular weight poly-γ-glutamic acid (γPGA) was found to increase levels of NK cell-mediated cytotoxicity and INF-γ secretion in C57BL/6 mice. Biodegradable γ-PGA nanoparticles have been evaluated for use as antigen delivery carriers and delivery of influenza virus hemagglutin (HA) vaccine. Additional life science applications for γ-PGA include uses in biodegradable fibers and nanofiber sheets, hydrogels, and cryoprotectants.