Poly-gamma-glutamic acid (PGA)

Poly-gamma-glutamic acid (PGA) is a naturally occurring, anionic biopolymer consisting of glutamate units linked by amide bonds between the alpha-amino and gamma-carboxylic acid groups. It is most notably produced by various Bacillus species, including Bacillus anthracis, where it forms a non-toxic, non-immunogenic capsule that is essential for the pathogen's survival within a host. By masking the bacteria from the host's immune system and inhibiting phagocytosis, PGA serves as a critical virulence factor. In medical research, PGA is targeted for the development of conjugate vaccines and monoclonal antibodies to treat anthrax. Additionally, its biodegradable and biocompatible properties make it a valuable scaffold for drug delivery systems, such as in the case of paclitaxel poliglumex, where it enhances drug solubility and targeting. The polymer is also explored in tissue engineering and wound healing due to its high water-retention capacity and low toxicity.

Other names

gamma-PGAPoly-gamma-D-glutamic acidPoly-D-glutamic acid capsuleH-poly(Glu)-OHPoliglumex

Targeting the poly-gamma-glutamic acid capsule facilitates opsonophagocytosis of the bacteria by the host immune system, thereby neutralizing the pathogen's primary defense mechanism. In drug delivery, PGA acts as a biodegradable carrier that improves the solubility and pharmacokinetic profile of conjugated cytotoxic agents.