Jeong Hun Kang

Bisphenol A in the Aquatic Environment and Its Endocrine-Disruptive Effects on Aquatic Organisms

Bisphenol A [BPA; 2,2-bis(4-hydroxyphenyl)propane], which is mainly used in the production of epoxy resins and polycarbonate plastics, is a known endocrine disruptor and is acutely toxic to aquatic organisms. Due to intensified usage of these products, exposure of organisms to BPA via several routes, such as the environment and food, has increased. The aquatic environment is an important area for the study of BPA. This report reviews the literature concerning contamination routes and degradation of BPA in the aquatic environment and its endocrine-disruptive effects on aquatic organisms.

Factors Influencing the Migration of Bisphenol A from Cans

The objective of this study was to determine whether there is a relationship between bisphenol A (BPA) migration from metal cans and container contents (glucose, sodium chloride, and vegetable oil), heating time, and/or temperature. Cans containing 5 to 20% glucose solution, 1 to 10% sodium chloride solution, and vegetable oils (corn, olive, and soybean oil) were heated at 121 degrees C for 30 min. Water samples were heated at 105 degrees C for 30 min and at 121 degrees C for 15, 30, and 60 min, respectively. In the test involving water samples, it was found that temperatures effect on BPA migration from cans can be more extensive than that of heating time. When cans were heated at 121 degrees C, the presence of 1 to 10% sodium chloride or vegetable oils greatly increased the migration of BPA from the cans. Moreover, the presence of 5 to 20% glucose in cans heated to 121 degrees C resulted in increased BPA migration relative to that for water controls.

Effects of bacterial counts and temperature on the biodegradation of bisphenol A in river water

Total 15 surface river waters were collected from thirteen different rivers to investigate a relationship of bacterial counts and temperature to the degradation of bisphenol A (BPA). Autoclaved and non-autoclaved river water samples were spiked with 0.2 mg/l BPA. The spiked samples were placed at temperatures of 4, 20, and 30 degrees C and analyzed by high performance liquid chromatography. BPA was degraded at all temperatures in the non-autoclaved samples. However, BPA in the autoclaved samples was not changed at all temperatures for 20 d. These results show that the primary factor of BPA degradation in river water is bacteria. Moreover, three groups [group A (> 10000 CFU/ml), group B (2000-10000 CFU/ml), and group C (< 2000 CFU/ml)], were made on the basis of bacterial counts of the samples. Half-lives for BPA degradation in groups A, B, and C were 2, 3, and 6 d at 30 degrees C and were 4, 5, and 7 d at 20 degrees C, respectively. But at 4 degrees C, the loss of BPA was about 40%, 20%, and 10% in groups A, B, and C for 20 d, respectively. Bacterial counts exerted an influence on BPA degradation in river water with temperature. Our results also show that BPA-degrading bacteria are widely distributed in river waters.

Measurement of homogeneous kinase activity for cell lysates based on the aggregation of gold nanoparticles

Protein kinases are involved in a number of signal transduction pathways and play a crucial role in many cell regulatory processes. Since malfunctions of cellular signaling have been linked with many common diseases, including cancers, considerable efforts have been made to develop analytical techniques for the high-throughput screening (HTS) of kinase activity and kinase-related drugs. Due to the increasing demand for faster screening processes, homogeneous detection methods that can both conduct enzymatic reactions and detect any resulting phosphorylated peptides under homogeneous solution conditions, and that do not require the elaborate washing steps needed for conventional ELISA, are receiving considerable attention. Most of the methods are based on fluorescence readout, and specially designed fluorescence probes are used not only to monitor the activity of purified kinase in real time, but also to detect any kinase activity in cell lysates. Colorimetric assays that make use of the aggregation of gold nanoparticles (GNPs) are simpler but sensitive methods, and can be adapted to HTS systems based on the microwell plate format. Colorimetric assays have been applied to the detection of biomolecules and to the evaluation of enzymatic activity. In most of these colorimetric assays, the GNPs are aggregated by “cross-linking molecules” that have multiple binding sites for molecules immobilized on the GNP surface. Brust’s group successfully detected kinase activity by utilizing this cross-linking-type GNP aggregation. Recently, an alternative GNP-aggregation-based detection system without the use of cross-linking molecules has emerged. In this detection system, biomacromolecules such as DNA and peptides are used as “stabilizers” or inversely as “coagulants” of GNPs. This system, which has been successful in the detection of DNA sequences and phosphatase activity, does not require GNP modifications or complicated procedures. Learning from these previous works, we sought to establish a system for detecting kinase activity, as shown in Figure 1. Here, cationic substrate

Design of Polymeric Carriers for Cancer-Specific Gene Targeting: Utilization of Abnormal Protein Kinase Cα Activation in Cancer Cells

We succeeded in cancer cell specific gene expression by using a polyplex responsive to protein kinase Calpha, which is activated in various types of cancer cells.

Determination of bisphenol A in canned pet foods

Bisphenol A (BPA) contamination of canned foods for human use has been studied, but there are no reports concerning BPA contamination of canned pet foods. The purpose of this study was to identify the levels of BPA in canned pet foods. A total of 26 samples (15 samples of cat food and 11 samples of dog food) were prepared for analysis by high-performance liquid chromatography. BPA in the samples was extracted with acetonitrile and fat in the sample extract was removed with hexane. Solid-phase extraction was used for sample clean-up prior to final analysis. The concentration of BPA ranged from 13 to 136 ng/g in canned cat food and from 11 to 206 ng/g in dog food. Also, to confirm that the BPA had originated from the can coating, distilled water was added to each washed empty can and the cans were autoclaved at 121 degrees C for 30 min. The concentration of BPA leached from empty cans was between 7 and 31 ng/ml.

Determination of bisphenol A in milk and dairy products by high-performance liquid chromatography with fluorescence detection.

This study was conducted to develop a selective and sensitive method for the determination of bisphenol A (BPA) levels in milk and dairy products. A method based on solvent extraction with acetonitrile and solid-phase extraction (SPE) was developed for the analysis of BPA in milk, yogurt, cream, butter, pudding, condensed milk, and flavored milk, and a method using two SPE cartridges (OASIS HLB and Florisil cartridge) for skim milk was also developed. The developed methods showed good recovery levels (77 to 102%) together with low detection limits (1 microg/liter for milk, yogurt, pudding, condensed milk, flavored milk, and skim milk and 3 microg/liter for cream and butter). These methods are simple, sensitive, and suitable for the analysis of BPA in milk and dairy products. When 40 milk and dairy products were analyzed by the proposed methods, BPA was not identified in noncanned products, but its levels ranged from 21 to 43 microg/kg in canned products, levels that were 60- to 140-fold lower than the migration limits in the European Union and Japan.

Bisphenol A migration from cans containing coffee and caffeine

This study was conducted to reconfirm the possibility and level of bisphenol A (BPA) migration from cans containing coffee and test the relationship between caffeine concentration and BPA migration from the can coating. BPA migration from cans containing decaffeinated and non-decaffeinated instant coffee averaged 66.2 and 84.0 ng ml-1, respectively. In our study, the possibility of BPA migration from cans containing coffee after processing was found. In addition, the more caffeine content in the water solution of caffeine increased, the more BPA migration grew. This means that caffeine can have an effect on BPA migration from the can coating.

Gold nanoparticle-based colorimetric assay for cancer diagnosis

A novel gold nanoparticle (GNP)-based colorimetric assay was developed for cancer diagnosis. This system is based on the noncrosslinking aggregation mechanism with a cationic protein kinase C (PKC) alpha-specific peptide substrate, which is used as a coagulant of citrate-coated GNP with anionic surface charges. The phosphorylation of peptide substrates by PKCalpha suppressed GNP aggregation, resulting in a red color, but in the case of non-phosphorylation, the color of the GNP solution changed from red to blue, indicating particle aggregation. Moreover, a correlation between the color change of the GNP dispersions and the level of activated PKCalpha was identified from experiments using cancer cell lines, or xenografted mouse cancer and normal mouse tissues. When our system was applied to human breast cancers and normal human breast tissues, cancer tissue lysates became red in color, indicating GNP dispersion, while all lysates from normal tissue turned the GNP solution blue. MALDI-TOF MS analysis and Western blotting experiment confirmed that these different results between cancer and normal tissues reflected the difference in PKCalpha activity. This study is the first report on the application of the GNP-based colorimetric assay to the diagnosis of cancer.

An intracellular kinase signal-responsive gene carrier for disordered cell-specific gene therapy

We have previously reported artificial gene-regulation systems responding to cyclic AMP-dependent protein kinase (PKA) using cationic polymer. This cationic polymer (PAK) was a graft-type polymer with an oligopeptide that is a substrate for PKA and could regulate gene-expression in a cell-free system. In the present study, we carried out a detailed characterization of the PAK-DNA complex (AFM observation and DLS measurement) and tried to apply this polymer to living cells. In the unstimulated NIH 3T3 cells, transfection of the PAK-DNA complex showed no expression of the delivered gene. This means that PAK formed a stable complex with DNA in the normal cells to totally suppress gene expression. In contrast, significant expression was seen when the PAK-DNA complex was delivered to forskolin-treated cells. Thus, activated PKA disintegrates the complexes even in living cells, resulting in gene expression. Our results indicate that this type of intracellular signal-responsive polymer will be useful for the cell-specific release of genes.