Gi Wook Kim

A facile and sensitive detection of organophosphorus chemicals by rapid aggregation of gold nanoparticles using organic compounds

Organophosphorus (OP) chemicals are highly effective insecticides and germicides, and are the most widely used in agriculture. Unfortunately, OP compounds are some of the most toxic substances to humans, even at very low doses. Because detecting OP residues in agricultural products is essential, simple, sensitive, and particularly rapid on-site detection methods are required. Gold nanoparticles (AuNPs) have been used as signal-enhancing detection probes in the field of biosensors due to their size-dependent optical properties. When imidazole was added to AuNPs mixed with OP compounds, the AuNPs was aggregated and their color changed to purple. This caused the appearance of a new peak at 660-670 nm, which could be measured within approximately 30 s. Therefore, this method allows the detection of OP compounds, including diazinon, iprobenfos, and edifenphos, on-site at part-per-billion (ppb) concentrations, and also affords a straightforward method. Furthermore, the method was successfully applied in the determination of OP compound in a real sample (river water) with satisfactory results.

Microbial inactivation and pesticide removal by remote exposure of atmospheric air plasma in confined environments.

Microbial inactivation and pesticide removal by remote exposure of atmospheric air plasma were investigated in confined environments, including an airtight box and commercial refrigerator. The relative sterilization ratios of remote plasma exposure in an airtight box were found to be affected by the distance from the plasma generator, the volume of box and the time of irradiation; however, over 99% saturation was obtained within only 120 s in all experiments. The sterilization of microorganisms and the removal of pesticide in a refrigerator with a volume of 292 l were also successfully achieved, resulting in over 99% inactivation or decontamination in a few minutes. Considering the reported results by direct plasma exposure and circulation, it can be concluded that the confined environment enhances the efficient irradiation of plasma by eliminating air flow. This system can be applied to the storage to keep agricultural products freshly and exclusion of harmful materials on the products.

In vivo synthesis of europium selenide nanoparticles and related cytotoxicity evaluation of human cells

Nanotechnology strives to combine new materials for development of noble nanoparticles. As the nanoparticles exhibit unique optical, electronic, and magnetic properties depending on their composition, developing safe, cost-effective and environmentally friendly technologies for the synthesis have become an important issue. In this study, in vivo synthesis of europium selenide (EuSe) nanoparticles was performed using recombinant Escherichia coli cells expressing heavy-metal binding proteins, phytochelatin synthase and metallothionein. The formation of EuSe nanoparticles was confirmed by using UV-vis spectroscopy, spectrofluorometry, X-ray diffraction, energy dispersive X-ray and transmission electron microscopy. The synthesized EuSe nanoparticles exhibited high fluorescence intensities as well as strong magnetic properties. Furthermore, anti-cancer effect of EuSe nanoparticles against cancer cell lines was investigated. This strategy for the biogenic synthesis of nanoparticles has a great potential as bioimaging tools and drug carrying agents in biomedical fields due to its simplicity and nontoxicity.

Development of a portable biosensor system for pesticide detection on a metal chip surface integrated with wireless communication

A novel low-cost ubiquitous sensor system was built on a microminiaturized electrochemical chip positioned on a gold electrode using a low-frequency wireless communication chipset to detect pesticides in situ. Different residual organophosphorus pesticides can be detected based on an enzyme reaction with electron transfer in the portable sensor system using a sensor array chip. This disposable, low-cost, and microminiaturized biosensor chip can be used to detect harmful residual agrichemicals within 3–4 min on a solid surface.

Development of a Separation and Detection System for Bacillus anthracisSpores Based on Peptide Conjugates Identified from Peptide Library

A simple, specific and rapid identification system against Bacillus anthracis spores was developed using specific capture peptides conjugated with a bead-based biosensor, which was tightly and specifically bound onto the spore surface of B. anthracis. We successfully detected and separated B. anthracis spores from the spores of B. thuringiensis and B. cereus using this peptide-magnetic bead conjugates by fluorescence and anthrax-specific analyses. For more convenient mediation of high-throughput detection against B. anthracis spores, streptavidin-biotin interactions of spore-peptide and spore-peptide-magnetic bead conjugates were performed, and we demonstrated the separation and detection of B. anthracis spores using this method. In the presence of mixed condition of several types of Bacillus spores, the B. anthracis spores were easily separated using the oligopeptide-conjugated magnetic beads, thus allowing the clear detection of B. anthracis spores from B. cereus, B. subtilis, and B. thuringiensis spores. This oligopeptidebased strategy was rapidly and unambiguously identified as little as one viable B. anthracis spore in less than 1 h with a simple binding assay format. When assessed for its effectiveness for specifically and selectively detection of environmental spores phylogenetically similar to B. anthracis spores, such as B. thuringiensis and B. cereus spores, the system was free of false-positive signals.

Development of specific immobilization method on gold surface and its application for determining cardiac risk

C-reactive protein (CRP) has been regarded as a most valuable marker of inflammation that had been shown in prediction of multiple prospective blood vascular studies such as an incident myocardial infarcion, stroke, peripheral arterial disease, and sudden cardiac death. A CRP detection system on a solid surface was developed using dual-antibody binding, which first antibody was immobilized by specific binding with Protein A via a fusion form with streptavidin. Second antibody bound with CRP was used for an electrochemical analysis on the gold chip surface. The fusion protein and antibodies could be successfully immobiized on the gold surface by strong biotin-streptavidin nteraction as examined by surface plasmon resonance analysis. The result showed that the limit of detection has reached at 2 pg/mL. Precision is adequate, and the wide-range response was shown with the concentraion of CRP between 0.01 pg/mL to 1 mg/mL. Signal difference for the same sample among different estabished chips is very low. Besides, the stable electrical signal was apparently maintained (~88% of initial response) for 35 days after storage at 4°C. This study provided a possibility for the development of portable chips or CRP detection, especially in the point-of-care use.