Minjung Cho

Acute toxicity and pharmacokinetics of 13 nm-sized PEG-coated gold nanoparticles

In general, gold nanoparticles are recognized as being as nontoxic. Still, there have been some reports on their toxicity, which has been shown to depend on the physical dimension, surface chemistry, and shape of the nanoparticles. In this study, we carry out an in vivo toxicity study using 13 nm-sized gold nanoparticles coated with PEG (MW 5000). In our findings the 13 nm sized PEG-coated gold nanoparticles were seen to induce acute inflammation and apoptosis in the liver. These nanoparticles were found to accumulate in the liver and spleen for up to 7 days after injection and to have long blood circulation times. In addition, transmission electron microscopy showed that numerous cytoplasmic vesicles and lysosomes of liver Kupffer cells and spleen macrophages contained the PEG-coated gold nanoparticles. These findings of toxicity and kinetics of PEG-coated gold nanoparticles may have important clinical implications regarding the safety issue as PEG-coated gold nanoparticles are widely used in biomedical applications.

Size-dependent tissue kinetics of PEG-coated gold nanoparticles.

Gold nanoparticles (AuNPs) can be used in various biomedical applications, however, very little is known about their size-dependent in vivo kinetics. Here, we performed a kinetic study in mice with different sizes of PEG-coated AuNPs. Small AuNPs (4 or 13nm) showed high levels in blood for 24h and were cleared by 7days, whereas large (100nm) AuNPs were completely cleared by 24h. All AuNPs in blood re-increased at 3months, which correlated with organ levels. Levels of small AuNPs were peaked at 7days in the liver and spleen and at 1month in the mesenteric lymph node, and remained high until 6months, with slow elimination. In contrast, large AuNPs were taken up rapidly ( approximately 30min) into the liver, spleen, and mesenteric lymph nodes with less elimination phase. TEM showed that AuNPs were entrapped in cytoplasmic vesicles and lysosomes of Kupffer cells and macrophages of spleen and mesenteric lymph node. Small AuNPs transiently activated CYP1A1 and 2B, phase I metabolic enzymes, in liver tissues from 24h to 7days, which mirrored with elevated gold levels in the liver. Large AuNPs did not affect the metabolic enzymes. Thus, propensity to accumulate in the reticuloendothelial organs and activation of phase I metabolic enzymes, suggest that extensive further studies are needed for practical in vivo applications.

Pulmonary toxicity and kinetic study of Cy5.5-conjugated superparamagnetic iron oxide nanoparticles by optical imaging

Recent advances in the development of nanotechnology and devices now make it possible to accurately deliver drugs or genes to the lung. Magnetic nanoparticles can be used as contrast agents, thermal therapy for cancer, and be made to concentrate to target sites through an external magnetic field. However, these advantages may also become problematic when taking into account safety and toxicological factors. This study demonstrated the pulmonary toxicity and kinetic profile of anti-biofouling polymer coated, Cy5.5-conjugated thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION) by optical imaging. Negatively charged, 36 nm-sized, Cy5.5-conjugated TCL-SPION was prepared for optical imaging probe. Cy5.5-conjugated TCL-SPION was intratracheally instilled into the lung by a non-surgical method. Cy5.5-conjugated TCL-SPION slightly induced pulmonary inflammation. The instilled nanoparticles were distributed mainly in the lung and excreted in the urine via glomerular filtration. Urinary excretion was peaked at 3 h after instillation. No toxicity was found under the concentration of 1.8 mg/kg and the half-lives of nanoparticles in the lung and urine were estimated to be about 14.4+/-0.54 h and 24.7+/-1.02 h, respectively. Although further studies are required, our results showed that Cy5.5-conjugated TCL-SPION can be a good candidate for use in pulmonary delivery vehicles and diagnostic probes.

Transient pulmonary fibrogenic effect induced by intratracheal instillation of ultrafine amorphous silica in A/J mice

In order to evaluate the degree of pulmonary fibrosis and to identify the fibrogenic mechanisms induced by ultrafine amorphous silica (UFAS), UFAS suspensions ( approximately 50microl) were instilled intratracheally into A/J mice at doses of 0, 2, 10 and 50mg/kg (n=5 per group). Mice were sacrificed at 24h, 1, 4 and 14 weeks after exposure. Gomoris trichrome staining revealed that UFAS induced severe alveolar epithelial thickening and pulmonary fibrosis at 1 week, though animals almost recovered at 4 and 14 weeks. The mRNA and protein levels of cytokines (IL-4, IL-10, IL-13 and IFN-gamma), matrix metalloproteinases (MMP-2, MMP-9 and MMP-10) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in lung tissues were significantly elevated at 24h and 1week post-treatment, though these levels decreased to near the control range at 4 and 14 weeks except IFN-gamma and MMP-2. These results demonstrate that UFAS can induce pulmonary fibrosis in the same way as crystalline silica. However, the degree of fibrosis observed was transient. This study shows that cytokines (IL-4, IL-10, IL-13 and IFN-gamma), MMPs (MMP-2, MMP-9 and MMP-10) and TIMP-1 play important roles in the fibrosis induced by the intratracheal instillation of UFAS.

Chitosan nanoparticles show rapid extrapulmonary tissue distribution and excretion with mild pulmonary inflammation to mice

Pulmonary delivery of nanoparticles (NP) conjugated with therapeutic agents has been considered recently for both lung disorders and systemic circulation. Hydrophobically modified glycol chitosan (HGC) NP have previously shown excellent deposition to the tumor site and non-destructive intracellular release. Here, we evaluated the kinetics and toxicity of HGC NP by intratracheal instillation to mice. HGC NP showed a positive charge and average hydrodynamic size was around 350 nm. The half-life of NP in the lung was determined as 131.97±50.51 h. NP showed rapid uptake into systemic circulation and excretion via urine which was peaked at 6h after instillation. Although HGC NP were distributed to several extrapulmonary organs, the levels were extremely low and transient. HGC NP induced transient neutrophilic pulmonary inflammation from 6h to day 3 after instillation. Expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and chemokine (MIP-1α) in lung showed an increase from 1h to 24h after instillation and recovered thereafter. Our findings suggest that HGC NP can be successful candidates for use as pulmonary delivery vehicles, owing to their excellent biocompatibility, transiency, and low pulmonary toxicity, and property of rapid elimination without accumulation.