Stability of naked pDNA (500 ng) and the pDNA (500 ng) uploaded into PEI25K, PEG-NP, and HNPs in the presence of FBS. They were incubated at 37 °C with 20% volume addition of FBS for 1, 4, 24, and 48 h. At the end of each determined time point, an aliquot of HNPs incubated with 20% FBS was added to 5 mg/mL Heparin to forcedly release the pDNA from HNPs to serve as controls. The released pDNAs were then visualized by agarose gel electrophoresis, followed by ethidium bromide staining and photographing using a Gel Doc XR+ System. The photos are representative pDNA images after agarose gel electrophoresis and ethidium bromide staining.