ABSTRACT
Gold nanorods, which have a strong surface plasmon band at the near-infrared region, absorb light energy which is then converted to heat. Since near-infrared light can penetrate deeply into tissue, gold nanorods are expected to be useful as photosensitizers for photothermal therapy. In this study, the length of the poly(ethylene glycol) (PEG) chain was optimized in order to stabilize the gold nanorods in the blood circulation after intravenous injection. PEG(5000)- and PEG(10000)-modified gold nanorods showed higher stability in the blood circulation compared with PEG(2000)- and PEG(20000)-modified gold nanorods. As a demonstration of photothermal tissue damage, PEG(5000)-modified gold nanorods were injected into the muscle in the hind limbs of a mouse, and then irradiated with near-infrared pulsed laser light. Significant tissue damage was observed only in the presence of gold nanorods and laser irradiation. We next injected the gold nanorods directly into subcutaneous tumors in mice, and then irradiated the tumor with near-infrared pulsed laser light. Significant suppression of tumor growth was observed. In the case of the intravenous injection of gold nanorods, the suppression of tumor growth was weaker than for the case of direct injection, indicating that the targeted delivery of gold nanorods to the tumor tissue is an important key to improve the therapeutic effect.
Subject(s)
Gold/chemistry , Gold/therapeutic use , Melanoma, Experimental/therapy , Nanotubes/chemistry , Polyethylene Glycols/chemistry , Animals , Gold/administration & dosage , Gold/pharmacokinetics , Hyperthermia, Induced , Injections, Intravenous , Lasers , Male , Mice , Mice, Inbred BALB C , Muscles/drug effects , Muscles/pathology , Muscles/radiation effects , Nanotubes/ultrastructure , Phototherapy , TemperatureABSTRACT
This study aimed to investigate the relationships between structures of gene carrier molecules and their activities for gene delivery into cells. We compared 2 types of poly(L-lysine) as carriers, that is, dendritic poly(L-lysine) (KG6) and linear poly(L-lysine) (PLL). KG6 formed a neutral DNA complex, and its DNA compaction level was weaker than that of PLL. The amount of DNA binding and uptake into cells mediated by PLL was 4-fold higher than that with KG6. However, KG6-mediated gene expression was 100-fold higher than that by PLL. Since pK(a) values of terminal amines of KG6 were lowered even though small amounts of DNA were internalized into cells, sufficient DNA amounts for effective gene expression escaped to the cytosol due to the proton sponge effect in the endosome. In addition, weakly compacted DNA with KG6 was advantageous in accessing RNA polymerase in the cell nucleus. On the other hand, PLL did not show the proton sponge effect in the endosome and resulted in strong compaction of DNA. Even though large DNA amounts were internalized into cells, most of the DNA would not take part in gene expression systems in the nucleus. Amount of induced cytokine production after intravenous injection of DNA complexes with KG6 and PLL was low, and was similar to the case when DNA was injected alone. Therefore, no significant difference in effects on cytokine production was observed between KG6 and PLL.
Subject(s)
Dendrimers/chemistry , Gene Transfer Techniques , Polylysine/chemistry , Animals , Binding Sites , CHO Cells , Cells, Cultured , Cricetinae , Cytokines/pharmacology , DNA/chemistry , DNA/drug effects , Gene Expression Regulation, Enzymologic/drug effects , Luciferases/drug effects , Luciferases/genetics , Molecular Structure , Structure-Activity RelationshipABSTRACT
Gold nanorods prepared in hexadecyltrimethylammonium bromide (CTAB) solution are expected to provide novel materials for photothermal therapy and photo-controlled drug delivery systems. Since gold nanorods stabilized with CTAB show strong cytotoxicity, we developed a technique to modify these with polyethyleneglycol (PEG) for medical applications. PEG-modification was achieved by adding mPEG-SH in the CTAB solution, then, excess CTAB was removed by dialysis. PEG-modified gold nanoparticles showed a nearly neutral surface, and had little cytotoxicity in vitro. Following intravenous injection into mice, 54% of injected PEG-modified gold nanoparticles were found in blood at 0.5 h after intravenous injection, whereas most of gold was detected in the liver in the case of original gold nanorods stabilized with CTAB.
Subject(s)
Gold/administration & dosage , Nanostructures , Polyethylene Glycols/administration & dosage , Animals , Cell Survival/drug effects , Cetrimonium , Cetrimonium Compounds/toxicity , Gold/pharmacokinetics , Gold/toxicity , HeLa Cells , Humans , Male , Mice , Tissue DistributionABSTRACT
This study aimed to investigate the benefits of combining the use of PEG-modified cationic gold nanoparticles with electroporation for in vivo gene delivery. PEG-modified cationic gold nanoparticles were prepared by NaBH(4) reduction of HAuCl(4) in the presence of 2-aminoethanethiol and mPEG-SH. Zeta-potential of the particles was nearly neutral (+0.1 mV). After forming complexes with plasmid DNA at a w/w ratio of 8.4, nanoparticle complexes were 90 nm for at least 60 min and showed a negative zeta-potential. After intravenous injection of DNA-nanoparticle complexes, 20% of gold were detected in blood at 120 min after injection and 5% of DNA were observed in blood after 5 min, suggesting that PEG-modified nanoparticles were stably circulating in the blood flow, but some of the DNA bound to particles degraded during circulation. When electroporation was applied to a lobe of the liver following injection of DNA-nanoparticle complexes, significant gene expression was specifically observed in the pulsed lobe. We concluded that PEG-modified nanoparticles maintained DNA more stably in the blood flow than in the case of naked DNA and electroporation assisted in restricted gene expression of circulating DNA in limited areas of the liver.
