In vitro enzymatic degradation of nanoparticles prepared from hydrophobically-modified poly(gamma-glutamic acid).

Amphiphilic poly(gamma-glutamic acid) (gamma-PGA) was prepared by the introduction of L-phenylalanine ethylester (L-PAE) as a side chain. This gamma-PGA-graft-L-PAE formed monodispersed nanoparticles in water. The particle size of the gamma-PGA nanoparticles could be controlled by the degree of L-PAE grafting. The hydrolytic degradation and enzymatic degradation by gamma-glutamyl transpeptidase (gamma-GTP) of these gamma-PGA nanoparticles was studied by gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The hydrolysis ratio of gamma-PGA was found to decrease upon increasing the hydrophilicity of the gamma-PGA. The degradation of the gamma-PGA backbone by gamma-GTP resulted in a dramatic change in nanoparticle morphology. With increasing time, the gamma-PGA nanoparticles reduced in size and finally disappeared completely.Time-course of the changes in the morphology of the gamma-PGA nanoparticles following incubation with gamma-glutamyl transpeptidase.