Eun-Min Cho

Detection of the mycotoxin citrinin using silver substrates and Raman spectroscopy.

We detected a trace amount of the mycotoxin citrinin using surface-enhanced Raman scattering (SERS) on silver nanoparticle (Ag NP) surfaces. The SERS substrate on hydrophobic Teflon films was also introduced to observe the citrinin peaks. A broad band at ∼1382cm(-1), which was ascribed to the symmetric carboxylate stretching mode, was observed in addition to an antisymmetric carboxylate stretching mode at ∼1568cm(-1) in the Raman spectra. The spectral feature indicated that citrinin would adsorb on Ag NPs via its carboxylate form. Based on density functional theory (DFT) calculations, vibrational mode analysis was performed to compare the Raman spectra of citrinin. DFT calculations also predicted that a bidentate bridge configuration through O15 and O16 atoms in citrinin would be the most stable on three Ag atoms. After treating with Ag NPs, observation of citrinin peaks was attempted in fungal cells of Penicillium citrinum. This work may provide useful insights into the direct observation of the hazardous citrinin mycotoxin using SERS by understanding its adsorption behaviors on Ag surfaces.

Gene expression profiles of human neuroblastoma cells exposed to CuO nanoparticles and Cu ions

Copper oxide nanoparticles (CuO NPs) are one of the most toxic metal oxide nanoparticles, but they have a wide range of applications in the manufacture of industrial and consumer products. While their beneficial aspects are widely acknowledged, the toxic effects of CuO NPs and Cu ions on the neuronal system may limit their use. Here, we propose a molecular mechanism underlying the response of human neuroblastoma SH-SY5Y cells to CuO NP and Cu ion exposure based on cDNA microarray data. SH-SY5Y cells exposed to CuO NPs and CuCl2 for 24 hours showed concentration-dependent cell death with similar IC50 values. The expression level of up-regulated genes in CuCl2-exposed cells was significantly higher than in CuO NP-exposed cells. CuO NP-exposed cells arrested the cell cycle in the G1/S/G2/M phases as a result of an up-regulation of INK4d, CYCE, RB, CDC6, CDC45, GADD45, and BUB1, while CuCl2-exposed cells mostly arrested the cell cycle in the G2/M phases as a result of CYCA, CYCB, CDK1, CDC20, PIK1, and BUB1 up-regulation. Our results suggest that the IC50 value had no significant relation with gene expression changes because the gene expression study may be in part due to cytotoxic mechanisms.

Interactions between the Antifungal Drug Myclobutanil and Gold and Silver Nanoparticles in Penicillium digitatum Investigated by Surface-Enhanced Raman Scattering:

Surface-enhanced Raman scattering (SERS) of an antifungal reagent, myclobutanil (MCB), was performed on Au and Ag nanoparticles (NPs) to estimate the drug-release behaviors in fungal cells. A density functional theory (DFT) calculation was introduced to predict a favorable binding site of MCB to either the Ag or Au atom. Myclobutanil was presumed to bind more strongly to Au than to Ag in their most stable, optimized geometries of the N4 atom in its 1,2,4-triazole unit binding to the metal atom. Strong intensities were observed in the Ag SERS spectra only at acidic pH values, whereas the most prominent peaks in the Au SERS spectra of MCB matched quite well with those of 1,2,4-triazole regardless of pH conditions. The Raman spectral intensities of the MCB-assembled Ag and Au NPs decreased after treatment with either potato dextrose agar (PDA) or glutathione (GSH). Darkfield microscopy and confocal SERS were performed to analyze the MCB-assembled metal NPs inside Penicillium digitatum fungal cells. The results suggested that MCB was released from the metal NPs in the intracellular GSH in the fungi because we observed only fungal cell peaks.