Plasmid DNA (pVAX1-NH36) was encapsulated in nanoparticles of poly-dL-lactic-coglycolic ( PLGA) functionalized with polyethylene glycol ( PEG) and folic acid (PLGA-PEG-FA) without losing integrity. PLGA-PEG-FA nanoparticles loaded with pVAX1-NH36 (pDNA-NPs) were prepared by using a double emulsification-solvent evaporation technique. PLGA-PEG-FA synthesis was verified by FT-IR and spectrophotometry methods. pVAX1-NH36 was replicated in Escherichia coli (E. coli) cell cultures. Atomic force microscopy (AFM) analysis confirmed pDNA-NPs size with an average diameter of 177-229 nm, depending on pVAX1-NH36 loading and zeta potentials were below 24 mV for all preparations. In vitro release studies confirmed a multiphase release profile for the duration of more than 30-days. Plasmid release kinetics were analyzed with a release model that considered simultaneous contributions of initial burst and degradation-relaxation of nanoparticles. Fitting of release model against experimental data presented excellent correlation. This mathematical analysis presents a novel approach to describe and predict the release of plasmid DNA from biodegradable nanoparticles.