Yeonho Jo

Sensitive detection of copper ions via ion-responsive fluorescence quenching of engineered porous silicon nanoparticles

Heavy metal pollution has been a problem since the advent of modern transportation, which despite efforts to curb emissions, continues to play a critical role in environmental pollution. Copper ions (Cu2+), in particular, are one of the more prevalent metals that have widespread detrimental ramifications. From this perspective, a simple and inexpensive method of detecting Cu2+ at the micromolar level would be highly desirable. In this study, we use porous silicon nanoparticles (NPs), obtained via anodic etching of Si wafers, as a basis for undecylenic acid (UDA)- or acrylic acid (AA)-mediated hydrosilylation. The resulting alkyl-terminated porous silicon nanoparticles (APS NPs) have enhanced fluorescence stability and intensity, and importantly, exhibit [Cu2+]-dependent quenching of fluorescence. After determining various aqueous sensing conditions for Cu2+, we demonstrate the use of APS NPs in two separate applications – a standard well-based paper kit and a portable layer-by-layer stick kit. Collectively, we demonstrate the potential of APS NPs in sensors for the effective detection of Cu2+.

Aptamer-conjugated live human immune cell based biosensors for the accurate detection of C-reactive protein.

C-reactive protein (CRP) is a pentameric protein that is present in the bloodstream during inflammatory events, e.g., liver failure, leukemia, and/or bacterial infection. The level of CRP indicates the progress and prognosis of certain diseases; it is therefore necessary to measure CRP levels in the blood accurately. The normal concentration of CRP is reported to be 1–3 mg/L. Inflammatory events increase the level of CRP by up to 500 times; accordingly, CRP is a biomarker of acute inflammatory disease. In this study, we demonstrated the preparation of DNA aptamer-conjugated peripheral blood mononuclear cells (Apt-PBMCs) that specifically capture human CRP. Live PBMCs functionalized with aptamers could detect different levels of human CRP by producing immune complexes with reporter antibody. The binding behavior of Apt-PBMCs toward highly concentrated CRP sites was also investigated. The immune responses of Apt-PBMCs were evaluated by measuring TNF-alpha secretion after stimulating the PBMCs with lipopolysaccharides. In summary, engineered Apt-PBMCs have potential applications as live cell based biosensors and for in vitro tracing of CRP secretion sites.

Perspectives on the nanotechnology applications of for the analytical detection of heavy metals in marine organisms

Heavy metals accumulate in organisms throughout the food chain and eventually end up in humans. Heavy metals can cause severe diseases and may even result in death. Therefore, concerns about heavy metal accumulation in marine organisms have increased in recent years. To determine solutions to this concern, the sensitive detection of heavy metals in marine organisms is required. Current detection techniques for heavy metals present in marine organisms have several limitations, such as complicated pre-treatment steps and a lengthy analysis time. Thus, there are increasing needs for the newly developed methods of detecting heavy metals in marine organisms. In this review, we focus here on (1) the current detection techniques available and (2) the application of newly emergent nanotechnology for the sensitive detection of heavy metals in marine organisms.

Strategies for the optimization of bead-immunoassays for the effective detection of target biomolecules

Immunoassays are analytical methods using antibody-specific reactions to analyze samples. Due to recent developments in antibody technology, the scope of potential samples has expanded to not only proteins, but also low molecular-weight compounds, carbohydrates, lipids, and microorganisms. Immunoassays have the advantage of being highly sensitive, capable of detecting small amounts, and thus have potential for application in biosensors. Immunoassays using magnetic beads have been developed and can be converted to more diverse platforms than the existing limited well plate-based assay. Furthermore, magnetic bead immunoassays detect analytical samples more quickly, and are becoming one of the most suitable immunoassay tools applicable to biosensors. However, their development requires optimization for the improvement of detection ability for specific samples. Therefore, we propose a guideline for solving detection problems occurring in magnetic bead immunoassay optimization processes. It is aimed to be a good reference, enabling researchers performing such optimization more quickly and efficiently

Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver MWCNTs were prepared by the reductive deposition of silver from an aqueous solution of AgNO3 on the oxidized MWCNTs. Given the unique color of the CNTs, it was not possible to apply them to the minimum inhibitory concentration or mitochondrial toxicity assays to evaluate the toxicity and antibacterial properties, since they would interfere with the assays. The inhibition zone and minimum bactericidal concentration for the Ag-MWCNTs were measured and Live/Dead and Trypan Blue assays were used to measure the toxicity and antibacterial properties without interfering with the color of the CNTs.

Use of nanoscale materials for the effective prevention and extermination of bacterial biofilms

Biofilms have been shown to cause most human infections. The prevention and extermination of bacterial biofilms has always presented a major challenge in the clinic. The failure of traditional antibiotics and the development of bacterial resistance against these measures is on the rise. Nanoscale materials possess the advantage of presenting enhanced surface properties of bulk materials, and are emerging as effective agents for deterring microbial growth. This review article summarizes the fundamentals of bacterial growth, biofilm formation, mechanisms for antibacterial technologies, and usage of nanoparticles for the prevention and extermination of biofilms. Further research is required with respect to the appropriate usage of nanoparticles for the effective control of biofilms to save human lives and reduce healthcare costs.

Probing characteristics of cancer cells cultured on engineered platforms simulating different microenvironments

Abstract In this study, we demonstrate cell culture platforms that can provide a microenvironment similar to in vivo conditions so that in vivo-compatible drug testing results can be obtained from the in vitro experiments. To realize such in vivo microenvironment-mimetic platforms, different culture platforms such as a three-dimensional (3D) cell aggregate film, fluidic environment within a microfluidic system or extracellular matrix (ECM) coating were established. The tumor cell growth rate and sensitivity to doxorubicin (DOX) were studied using the glioblastoma cell line T98G. When 3 D spheroids were cultured, they grew significantly slower than under other culture conditions. When the cells were treated with DOX, the anticancer drug could not efficiently penetrate the 3 D spheroids to inhibit cell growth. When cultured on the Matrigel-coated culture vessel, T98G cells grew even in the presence of DOX, demonstrating chemoresistance. Nonetheless, in the 2D culture plate and in the microfluidic chip, cell growth decreased with DOX treatment and the binding ability was lost. These results indicate that the cells reacted differently to the same anticancer drug depending on the culture microenvironment. We believe that the development of a more physiologically relevant tumor cell culture platform will lead to more reliable antitumor drug responses.