Seung Hyuck Bang

Toxicity Assessment of Titanium (IV) Oxide Nanoparticles Using Daphnia magna(Water Flea)

Objectives Titanium dioxide (TiO2), a common nanoparticle widely used in industrial production, is one of nano-sized materials. The purpose of this study was to determine the acute and chronic toxicity of TiO2 using different size and various concentrations on Daphnia magna. Methods In the acute toxicity test, four concentrations (0, 0.5, 4, and 8 mM) for TiO2 with 250 or 500 nm and five concentrations (0, 0.25, 0.5, 0.75, and 1 mM) for TiO2 with 21 nm were selected to analyze the toxic effect to three groups of ten daphnia neonates over 96 hours. In addition, to better understand their toxicity, chronic toxicity was examined over 21 days using 0, 1, and 10 mM for each type of TiO2. Results Our results showed that all organisms died before the reproduction time at a concentration of 10 mM of TiO2. In addition, the exposure of anatase (21 nm) particles were more toxic to D. magna, comparing with that of anatase (250 nm) and rutile (500 nm) particles. Conclusions This study indicated that TiO2 had adverse impacts on the survival, growth and reproduction of D. magna after the 21days exposure. In addition, the number of test organisms that were able to reproduce neonates gradually were reduced as the size of TiO2 tested was decreased.

Increased In Vitro Lysosomal Function in Oxidative Stress-Induced Cell Lines

Exposure of mammalian cells to oxidative stress alters lysosomal enzymes. Through cytochemical analysis of lysosomes with LysoTracker, we demonstrated that the number and fluorescent intensity of lysosome-like organelles in HeLa cells increased with exposure to hydrogen peroxide (H2O2), 6-hydroxydopamine (6-OHDA), and UVB irradiation. The lysosomes isolated from HeLa cells exposed to three oxidative stressors showed the enhanced antimicrobial activity against Escherichia coli. Further, when lysosomes that were isolated from HeLa cells exposed by oxidative stress were treated to normal HeLa cells, the viability of the HeLa cells was drastically reduced, suggesting increased in vitro lysosomal function (i.e., antimicrobial activity, apoptotic cell death). In addition, we also found that cathepsin B and D were implicated in increased in vitro lysosomal function when isolated from HeLa cells exposed by oxidative stress. Decrease in cathepsin B activity and increase in cathepsin D activity were observed in lysosomes isolated from HeLa cells after treatment with H2O2, 6-ODHA, or UVB, but cathepsin B and D were not the sole factors to induce cell death by in vitro lysosomal function. Therefore, these studies suggest a new approach to use lysosomes as antimicrobial agents and as new materials for treating cancer cell lines.

Outstanding Antibiofilm Features of Quanta-CuO Film on Glass Surface

Intelligently designed surface nanoarchitecture provides defined control over the behavior of cells and biomolecules at the solid-liquid interface. In this study, CuO quantum dots (quanta-CuO; ∼3-5 nm) were synthesized by a simple, low-temperature solution process and further formulated as paint to construct quanta-CuO thin film on glass. Surface morphological characterizations of the as-coated glass surface reveal a uniform film thickness (∼120 ± 10 nm) with homogeneous distribution of quanta-CuO. The antibiofilm assay showed a very high contact bacteria-killing capacity of as-coated quanta-CuO glass surfaces toward Staphylococcus aureus and Escherichia coli. This efficient antibacterial/antibiofilm activity was ascribed to the intracellular reactive oxygen species (ROS) generated by the quanta-CuO attached to the bacterial cells, which leads to an oxidative assault and finally results in bacterial cell death. Although there is a significant debate regarding the CuO nanostructures antibacterial mode of action, we propose both contact killing and/or copper ion release killing mechanisms for the antibiofilm activity of quanta-CuO paint. Moreover, synergism of quanta-CuO with conventional antibiotics was also found to further enhance the antibacterial efficacy of commonly used antibiotics. Collectively, this state-of-the-art design of quanta-CuO coated glass can be envisioned as promising candidates for various biomedical and environmental device coatings.

Evaluation of whole lysosomal enzymes directly immobilized on titanium (IV) oxide used in the development of antimicrobial agents

Lysosomal enzymes isolated from egg white were directly immobilized on titanium (IV) oxide (TiO(2)) particles using shaking methods (150 rpm, room temperature, 10 min), and the immobilization efficiency, activity, and stability of lysosomal enzymes immobilized on TiO(2) were evaluated. Of the various mass ratios (w/w) of lysosomal enzymes to TiO(2) tested, we found that 100% immobilization efficiency was observed at a ratio of 1:20 (enzymes:TiO(2); w/w). Furthermore, the antimicrobial activities of the immobilized lysosomal enzymes were confirmed using viable cell counts against Escherichia coli. Our results showed that the antimicrobial activity of immobilized lysosomal enzymes is stable and can be maintained up to one month, but the antimicrobial activity of free enzymes without immobilization completely disappeared after five days in storage. In addition, enhanced immobilization efficiency was shown in TiO(2) pretreated with a divalent, positively charged ion, Ca(2+), and the antimicrobial activity for E. coli increased as a function of increasing ratio of immobilized enzymes. However, K(+), a monovalent, positively charged ion, did not have any positive effect on immobilization or antimicrobial activity. Finally, we suggest that activity and stability of immobilized lysosomal enzymes can be maintained for a longer time than those properties of free lysosomal enzymes.

Phenol degradation activity and reusability of Corynebacterium glutamicum coated with NH2-functionalized silica-encapsulated Fe3O4 nanoparticles

In this study, a novel method to immobilize and separate Corynebacterium glutamicum for phenol degradation was developed using Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were encapsulated with silica and functionalized with NH(2) groups to enhance their capacity to adsorb on the cell surface. The results showed that the NH(2)-functionalized silica-encapsulated Fe(3)O(4) NPs strongly adsorbed on the cell surface of C. glutamicum during 32 d culture without any interruptions of their normal cell growth. The coated C. glutamicum were easily separated from the culture broth within 2 min by applying an external magnetic field Also, the coated C.glutamicum were able to completely degrade 50 ppm phenol in the culture broth after 8d culture at 30 °C. Concerning reusability, the coated cells could completely degrade phenol during the first 2 cycles, and retain ~60% activity of phenol degradation for the third and four cycles.

Acute and chronic toxicity assessment and the gene expression of Dhb , Vtg , Arnt , CYP4 , and CYP314 in Daphnia magna exposed to pharmaceuticals

The exposure of environment to pharmaceuticals disturbs the aquatic ecosystem. In this study,the effect of commonly used pharmaceutical compounds such as caffeine, ibuprofen, aspirin, and tetracycline has been investigated by the toxicity assay using Daphnia magna. The acute (48 h) and chronic (21 days) toxicity assays have been performed using Daphnia magna. The lethal concentrations of caffeine, ibuprofen, aspirin, and tetracycline with 50% mortality (LC50) have been determined as ∼445.3, 91.5, 310, and 90.8 mg/L, respectively. In the chronic toxicity test, low concentrations such as 1%, 2%, 10%, 20% LC50 of the pharmaceuticals were used to expose the organisms for 21 days. The effect of these pharmaceuticals on the molecular responses in the organisms has been studied from the gene expression level of five different biomarkers in Daphnia magna (Dhb, Vtg, Arnt, CYP4, and CYP314) after 48 h and 21 days exposure to the testing pharmaceuticals. The results show that five genes show different responsive patterns when Daphnia magna was under stressful conditions caused by caffeine, ibuprofen, aspirin, and tetracycline. During exposure to caffeine, only the response for the Dhb gene increased in the acute test, whereas all other genes, except Dhb gene, were down regulated in the chronic text. In contrast, in the acute and chronic toxicity test for ibuprofen, the responses for Arnt and CYP4 genes were reduced, respectively. Moreover, after 48 h exposure to aspirin, all other genes, except the Dhb gene, were down regulated. In the chronic test using tetracycline, five genes expression of D. magna were affected.

Toxic detection in mine water based on proteomic analysis of lysosomal enzymes in Saccharomyces cerevisiae

Objectives Lysosome is the cell-organelle which is commonly used as biomonitoring tool in environmental pollution. In this study, the lysosomal proteomic of the yeast Saccharomyces cerevisiae was analyzed for utilization in the detection of toxic substances in mine water samples. Methods This work informs the expression of lysosomal proteomic in yeast in response with toxic chemicals, such as sodium meta-arsenite and tetracycline, for screening specific biomarkers. After that, a recombinant yeast contained this biomarker were constructed for toxic detection in pure toxic chemicals and mine water samples. Results Each chemical had an optimal dose at which the fluorescent protein intensity reached the peak. In the case of water samples, the yeast showed the response with sample 1, 3, 4, and 5; whereas there is no response with sample 2, 6, and 7. Conclusions The recombinant yeast showed a high ability of toxic detection in response with several chemicals such as heavy metals and pharmaceuticals. In the case of mine water samples, the response varied depending on the sample content.

Proteomic analysis of Daphnia magna exposed to caffeine, ibuprofen, aspirin and tetracycline

The toxicity of pharmaceuticals thrown indiscriminately adversely affects the environment. In this study, the impact of caffeine, ibuprofen, aspirin and tetracycline has been examined through toxicity assay based proteomic analysis. Proteomic profile in Daphnia magna was analyzed by two-dimensional electrophoresis with pH in the range 3 to 10. The LC50 of caffeine, ibuprofen, aspirin and tetracycline determined as 445.3, 91.5, 310 and 90 mg/L, respectively, was used to expose to D. magna grown for 48 hour before isolating total proteins. The results show that the expression pattern of protein’s profile in D. magna gets changed due to the toxicity of caffeine, ibuprofen, aspirin and tetracycline. A large number of proteins expressed differently in D. magna in comparison to those exposed to various pharmaceuticals. The results showed that 18 up- and 1 down-regulation spot in relation to caffeine exposure; 24 up- and 6 down-regulation spots in relation to ibuprofen exposure; 3 up- and 4 down-regulation spots in relation to aspirin exposure and 10 up- and 3 down-regulation spots in relation to tetracycline exposure have been observed. Thus, the present systemic approach using proteomic analysis is very helpful in screening novel biomarkers for pharmaceuticals induced hazardous effects.

Effect of GTP-binding protein (YPT1 protein) on the enhanced yeast vacuolar activity

Yeast GTP-binding protein (YPT1 protein) has been reported to function in the early stages of the secretory pathway. Particularly, YPT1 protein is observed to regulate both the endoplasmic reticulum-to-Golgi transport and the autophagy. Therefore, the YPT1 protein overexpressed in yeast vacuoles is expected to enhance antimicrobial and anticancer activity. The enhancement of yeast vacuolar activity under the overexpression of YPT1 was evaluated by the analysis of lysozyme activity, antimicrobial activity against Escherichia coli and Staphylococcus aureus, and MTT assay against HeLa cell lines. Additionally, the rise in concentration of some important proteinases inside the vacuole, such as proteinase A, proteinase B, and vacuolar carboxypeptidase Y (CPY) were also recorded using a 2DE technique. All results imply YPT1 involvement in the recruitment of some specific proteinases into vacuoles, which leads to the enhancement of vacuolar activity. Since these there proteinases belong to the CPY pathway, YPT1 is even believed to up-regulate this trafficking pathway in yeast cells. Future studies, however, should be carried out to discover the mechanisms that allow YPT1 to recruit these proteins into yeast vacuoles.

Advances in antimicrobial agents based lysosomes

The emergence of drug resistance in common bacteria and the rapid emergence of new infections have motivated the need for the development of eco-friendly agents that do not contain any organic or inorganic material. The development of therapeutic agents which are able to remove or treat bacteria and cancer cell is very important and it should be very rapid, cost effective and nontoxic. Lysosomes are important against all other subcellular constituents due to their polymorphism as well as their involvement in both physiological and pathological processes. Lysosomes, which generally contain 50–60 hydrolases that constitute the cellular site for bulk macromolecule degradation, function to mediate several processes in the cell. They are single membrane bound cytoplasmic organelles involved in the degradation of intracellular protein. Lysosomal enzymes in lysosomes can be used as endocytosis for inhibiting bacteria phagocytosis as well as in antimicrobial activity. Many attempts have been made to increase the lysosomal activity by using different sources and significant changes have been observed in lysosome activity under starvation condition of reduced glucose. The treatment of some of the reagents and optimized aging cell with cell passage has also been used to evaluate an increase in their antimicrobial activity. The antimicrobial activity of lysosomes with various bacteria extracted from different sources has been observed. In the present review, the antimicrobial activity of lysosomes isolated from various sources such as human, bacteria and animals against different microorganisms has been discussed.