Jinkyu Roh

Functional Analysis of TiO2 Nanoparticle Toxicity in Three Plant Species

Titanium dioxide nanoparticles (nano-TiO2) are manufactured and used worldwide in large quantities. However, phytotoxicity research on nano-TiO2 has yielded confusing results, ranging from strong toxicity to positive effects. Therefore, in this research, the effects of nano-TiO2 on the germination and root elongation of seed and seedlings were studied. Additionally, the uptake and physiological responses of mature plants were investigated. Physical chemistry data were analyzed to assess the availability of nano-TiO2. Finally, a hydroponic system designed to overcome nano-TiO2 precipitation was used to reproduce the environmental conditions of actual fields. Nano-TiO2 did not have any effect on seed germination or on most of the plant species tested. Nano-TiO2 had positive effects on root elongation in some species. No physiological differences in enzyme activities or chlorophyll content were detected, even though the plants absorbed nano-TiO2. Physical chemistry data showed that nano-TiO2 agglomerated rapidly and formed particles with much bigger hydrodynamic diameters, even in distilled water and especially in a hydroponic system. Furthermore, agglomerated nano-TiO2 formed precipitates; this would be more severe in an actual field. Consequently, nano-TiO2 would not be also readily available to plants and would not cause any significant effects on plants. Our results and other reports suggest that titanium itself is not phytotoxic, even though plants absorb titanium. In conclusion, nano-TiO2 is not toxic to the three plant species, in vitro or in situ.

Rapid, reversible preparation of size-controllable silver nanoplates by chemical redox.

Citrate-stabilized silver nanoplates (AgNPs) were prepared using a seed-mediated growth method. The AgNP shape and size were controlled using potassium permanganate (KMnO(4)) as an oxidant and ascorbic acid (AA) as a reductant. Using KMnO(4), 42 nm nanoplates were changed to 22.9 nm nanodisks because of the release of silver ions. Using AA, the oxidized AgNPs were resynthesized to their initial plate form. These results are similar to those obtained using photoinduced shape control of silver nanoparticles; however, the chemical oxidation/reduction method can control the shape of AgNPs, both quantitatively and reversibly. In addition, because of redox-related visible spectral changes, solution color varies with AgNPs size. That feature may be useful in various applications.

Induction of Inflammatory Responses by Carbon Fullerene (C60) in Cultured RAW264.7 Cells and in Intraperitoneally Injected Mice

As the use of carbon fullerene increases in the chemical industry, the concern over its biological and toxicological effects is also increasing. In this study, the suspension of carbon fullerene (C60) in phosphate buffered saline was prepared and toxicity was investigated using cultured RAW 264.7 and in intraperitoneally injected mice, respectively. The average size of carbon fullerene in the suspension was 53.7 ± 26.5 nm when determined by particle size analyzer. Cell viability was significantly decreased by the exposure of carbon fullerene (0.25~2.00 μg/ml) for 96 hrs in the cultured RAW 264.7 cells. Intracellular reduced glutathione (GSH) level was also decreased compared to the level of the non-treated control group during the exposure period, while the level of nitric oxide was increased. When mice were intraperitoneally injected with carbon fullerene, serum cytokine levels of IL-1 and IL-6 were increased with the increased expression of inflammatory genes in peritoneal macrophage and T cell distribution in blood lymphocytes.The results suggested inflammatory responses were induced by carbon fullerene.

Shape‐Persistent Replica Synthesis of Gold/Silver Bimetallic Nanoplates Using Tailored Silica Cages

Shape-persistent replica synthesis of Au/Ag bimetallic nanoplates is invented. Using a tailored silica cage as a template for the synthesis, a successful shape-replication of Au/Ag bimetallic nanoplate is achieved at the cage core having geometry of initial Ag nanoplate. This work can open up the simple fabrication of multicomponent metallic particles, with nanogeometry being defined early at the initial stage.

Dual-fluorophore silica microspheres for ratiometric acidic pH sensing

AbstractEncapsulation of fluorophores in silica matrix offers many advantages such inhibition of photobleaching and possibilities for ratiometric pH sensing. Dualfluorophore pH-responsive silica microspheres, incorporating pyranine (HPTS) and rhodamine B isothiocyanate (RBITC), were synthesized by Stöber method, followed layer-by-layer depositions. The resulting dual-fluorophore silica microspheres were then characterized by SEM, TEM, fluorescence spectroscopy and imaging. The incorporation of two dyes in the microspheres allowed ratiometric quantification of pH. The ratiometric approach has been proven to reduce the influences of external perturbations and unequal dye concentration in silica matrix during measurements. The dynamic range for pH was from 1.5 to 4. The sensing microspheres could be applied to determine acidic pH. Additionally, the sensing microspheres exhibited a high colloidal and long-term stability and also allow a fast detection of pH due the porosity of the microspheres. Such structured microspheres could be optimized, using multiple dyes for multianalyte detection.

Optimal Photoluminescence Achieved by Control of Photopolymerization for Diacetylene Derivatives That Induce Reversible, Partially Reversible, and Irreversible Responses

Abstract

Dual-fluorophore raspberry-like nanohybrids for ratiometric pH sensing

We report on the development of raspberry-like silica structures formed by the adsorption of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS)@silica nanoparticles (NPs) on rhodamine B isothiocyanate (RBTIC)@silica NPs for ratiometric fluorescence-based pH sensing. To overcome the well-known problem of dye leaching which occurs during encapsulation of anionic HPTS dye in silica NPs, we utilized a polyelectrolyte-assisted incorporation of the anionic HPTS. The morphological and optical characterization of the as-synthesized dye-doped NPs and the resulting nanohybrids were carried out. The pH-sensitive dye, HPTS, incorporated in the HPTS-doped silica NPs provided a pH-dependent fluorescence response while the RBITC-doped silica provided the reference signal for ratiometric sensing. We evaluated the effectiveness of the nanohybrids for pH sensing; the ratio of the fluorescence emission intensity at 510 nm and 583 nm at excitation wavelengths of 454 nm and 555 nm, respectively. The results showed a dynamic response in the acidic pH range. With this approach, nanohybrids containing different dyes or receptors could be developed for multifunctioning and multiplexing applications.

Polydiacetylene/Anti-HBs Nanobio-Complexes for Visible and Fluorescent Detection of Hepatitis B Surface Antigen on Nitrocellulose Membrane

The immunochromatographic assay (ICA) using a nitrocellulose (NC) membrane offers several advantages. This technique is a rapid and straightforward method in contrast to other immunoassays. Polydiacetylene (PDA) vesicles have unique optical properties, displaying red color and red fluorescence at the same time. In this system, red-phase PDA vesicles are used as a fluorescent dye as well as a surface for immobilized hepatitis B surface antibody (HBsAb). PDA has a remarkable stability compared with other fluorescent dyes. In this study, the most suitable PDA/HBsAb complexes are introduced for detecting hepatitis B surface antigen (HBsAg). Then, the PDA/HBsAb complexes affixed antibody is attached to NC membrane, which has two lines to confirm detection of HBsAg. The main advantage of this system is that the detection of HBsAg can be observed in both visible and fluorescent images due to the optical properties of polydiacetylene. Detection of HBsAg is observed up to 0.1 ng mL-1 by fluorescent analysis and confirmed by red line on the NC membrane up to 1 ng mL-1 (HBsAg) using the naked eye. Consequently, these results show that PDA/HBsAb complexes were successfully applied to ICA for the diagnosis of hepatitis B.