| Preparations of microparticles as controlled drug delivery system have been widely studied and have got success. Nanoparticles are those microparticles that their diameter between l-1000nm and carry drugs. Nowdays, nanoparticles as nonviral gene delivery system is on focus. With nanoparticles as gene carrier, the stability of the gene in vitro can be improved and the gene can be protected from nuclease. Also more gene can be deliveried into cells and at the same time transfection efficiency can be increased.so the protein that needed can be expressed efficientlyThe plasmid gene of enhanced green fluorescence protein (pIRES2-EGFP) and the plasmid gene of butyrylcholinesterase (pRc/CMV-BchE) are selected as model gene. Surface chemical modification and transfection efficiency are studied with pIRES2-EGFP nanoparticles, The conditions of preparing pRc/CMV-BchE -Chitosan nanoparticles were optimized. The pRc/CMV-BchE -Chitosan nanoparticles were prepared according to the optimum conditions. The properties of nanoparticles were studied systematically and the transfection efficiency in vitro and in vivo were investigated preliminarily.The pRc/CMV-BchE -Chitosan nanoparticles were prepared using complexcoacervation method with the plasmid gene of butyrylcholinesterase (pRc/CMV-BchE). The effects of Cchitosan, C PRC/CMV-BCHE , CNa2so4, pH and treact on the mean diameter are investigated. The mean diameter gradually decreased with CChitosan increasing and increased with C pRc/cMv-BchE increasing, Co-action of the factor Cchjtosan and C pRc/cMv-BchE had marked in the optimum preparative conditions. The CNa2SO4, pH and treact had almost no effect on the mean diameter. According to the result of transmissionelectronic microscopy (TEM), the optimum preparative conditions is concentration of chitosan (300μg/mL), concentration of pRc/CMV-BchE(100 μg/mL), concentration of Na2SO4 (8mM), time of reaction(30second), and pH(5.5).The pRc/CMV-BchE -Chitosan nanoparticles according to the optimum preparative conditions were prepared. The results of observing through TEM and SEM showed that pRc/CMV-BchE -Chitosan nanoparticles were almost spherical and the mean diameter is less than lOOnm. The Z average mean diameter, intensity mean diameter, volume mean diameter, number mean diameter, polydispersity, zeta potential, were 218.1nm, 238 nm, 421 nm, 69.7 nm, 0.291 and + 15.9 mV, they are determined by photon correlation spectroscopy (PCS). The encapsulating efficiency and loading efficiency are 98.64% and 38.52%, respectively. It was determined with fluorescence spectrometer and UV. According to studies above, it was concluded that the most pRc/CMV-BchE is carried by nanoparticles and the chitosan has very strong ability of carry plasmid gene.To achieve hepatic targeting gene delivery and avoid be cleared up by immune system, the DNA -Chitosan nanoparticles surface chemical modification route was designed. Galactosyated bovine serum albumin (Galn-BSA) as the ligand of galactose receptor was prepared through the reductive animation method. The surface of the pRc/CMV-BchE-Chitosan nanoparticles was modified with polyethylene glycol (PEG). The modification results showed that the dispersity of the modified pRc/CMV-BchE -Chitosan nanoparticles was good, the mean diameter and the morphology of nanoparticles had no little change. For HepG2 cells, the transfection efficiency of the PEG-pIRES2-EGFP -Chitosan nanoparticles slightly rose. But Galactosyated bovineserum albumin did not increase the transfection efficiency more.The transfection ability of pIRES2-EGFP -Chitosan nanoparticles was evaluated using human embryonic kidney cells (HEK293). The determination results of fluorescence microscopy and flow cytometer showed that the chitosan nanoparticles could deliver pIRES2-EGFP into cells and the pIRES2-EGFP expressed green fluorescence protein, which proved that chitosan nanoparticles gene delivery systemwas feasible. When administered after 3 days with dose 4 g , the transfection ability of pIRES2-EGFP...
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