Dual role of blue luminescent MoS2 quantum dots in fluorescence resonance energy transfer phenomenon.

Homogeneous blue luminescent MoS2 quantum dots are fabricated by using a lithium intercalation method from MoS2 nanoparticles, and the unique blue photoluminescence property is utilized in the Alexa Fluor 430-dsDNA-MoS2 FRET system, demonstrating the dual function of MoS2 quantum dots as a donor and an acceptor.

Photoluminescent graphene oxide microarray for multiplex heavy metal ion analysis.

An aptamer-linked graphene oxide (GO) microarray is synthesized for multiplex heavy metal ion detection. Fluorescent nanosized GO sheets are micropatterned, and specific aptamers targeting Ag(+) and Hg(2+) are immobilized on the GO array. Upon capture of the target heavy metal ions, electron transfer occurs between the GO (donors) and the heavy metal ions (acceptors), leading to fluorescence quenching of the GO.

Effect of chemical and structural feature of graphene on surface enhanced Raman scattering.

Graphene nanomaterial has been reported as a chemical mechanism based surface-enhanced Raman scattering (SERS) substrate which has advantages of accuracy in the peak assignment with less peak shift and broader choice in the laser sources. Here we present a systematic study to investigate the effect of graphene oxide (GO), reduced graphene oxide (RGO), two- and three-dimensional (2D and 3D) graphene structure as well as their nanocomposites with gold nanoparticle (Au NP) as a SERS substrate to detect Rhodamine 6G (R6G) molecules. Compared with a glass substrate, the Raman signals were enhanced by 1.6 x 10(2) and 1.0 x 10(2)-fold in the 2D GO and 2D RGO, respectively, while 3D GO structure shows 2.2 x 10(2)-fold increase in the intensity over the glass substrate. These results imply that the GO is a better SERS substrate than the corresponding RGO, and the 3D structure of GO improves the sensitivity more than the 2D GO sheets by 1.4-fold due to the local electromagnetic effect derived from the oxygen-containing functional groups and the 3D morphology of GO. The Au NP composite with the 2D GO and 3D GO shows the increased Raman signal over the 2D GO and 3D GO by 5-fold and 3.8-fold, respectively, suggesting the synergistic effect of the Au NP on the graphene in the SERS measurements. These results imply that the optimization of the structural feature and chemical modification of the graphene is necessary to maximize the capability of graphene as a SERS substrate to detect various chemical and biomoleculs with high sensitivity.

Enzyme incorporated microfluidic device for in-situ glucose detection in water-in-air microdroplets.

Droplet generating microfluidic systems can provide miniaturized bioanalytical tools by using the homogenous and high-throughput droplets as nanoreactors. In this study, we demonstrated a sensitive and in-situ glucose monitoring system using water-in-air droplets in an enzyme incorporated microfluidic device. A thin film structure of a glucose oxidase (GOx) enzyme immobilized hydrogel was constructed in the middle of the microfluidic channel, and nanoliter scaled water-in-air droplets which contain a glucose sample, horseradish peroxidase (HRP), and an Amplex Red substrate were generated by flow focusing of water phase with air. Once the droplets passed through the enzyme trapped hydrogel, the droplets temporarily halted and a GOx mediated catalytic reaction with glucose proceeded, resulting in producing fluorescent resorufin products in the droplets. With optimized conditions such as the thickness of a hydrogel film and the size and flowing rate of droplets, fluorescence intensities of the released droplets linearly increased in proportional to the glucose concentration up to 3mM, and the limit of detection was calculated as 6.64µM. A spiked glucose in a real urine sample was also successfully analyzed, and the functionality of the proposed enzyme immobilized microfluidic chip was maintained for at least two weeks without loss of enzymatic activity and detection sensitivity. Thus, our methodology suggests a novel droplet based glucose sensing chip which can monitor glucose in a real-time and high-throughput manner.

Synthesis of a 3D graphite microball using a microfluidic droplet generator and its polymer composite with core-shell structure.

Spherical 3D graphite microballs (3D GMs) and their nanohybrids (3D GM-Fe3O4 nanoparticles) were synthesized by using a microfluidic droplet generator and a thermal evaporation-induced capillary compression method. Using the 3D GM-Fe3O4 nanoparticle as a support for polymerization, 3D GM-polypyrrole composites were produced with a unique core-shell structure.

Role of glycosylation in the anticancer activity of antibacterial peptides against breast cancer cells.

Antibacterial peptides (ABPs) with cancer-selective toxicity have received much more attention as alternative chemotherapeutic agents in recent years. However, the basis of their anticancer activity remains unclear. The modification of cell surface glycosylation is a characteristic of cancer cells. The present study investigated the effect of glycosylation, in particular sialic acid, on the anticancer activity of ABPs. We showed that aurein 1.2, buforin IIb and BMAP-28m exhibited selective cytotoxicity toward MX-1 and MCF-7 breast cancer cells. The binding activity, cytotoxicity and apoptotic activity of ABPs were enhanced by the presence of O-, N-glycoproteins, gangliosides and sialic acid on the surface of breast cancer cells. Among N-, O-glycoproteins and ganglioside, O-glycoproteins almost had the strongest effect on the binding and cytotoxicity of the three peptides. Further, up-regulation of hST6Gal1 in CHO-K1 cells enhanced the susceptibility of cells to these peptides. Finally, the growth of MX-1 xenograft tumors in mice was significantly suppressed by buforin IIb treatment, which was associated with induction of apoptosis and inhibition of vascularization. These data demonstrate that the three peptides bind to breast cancer cells via an interaction with surface O-, N-glycoproteins and gangliosides. Sialic acids act as key glycan binding sites for cationic ABP binding to glycoproteins and gangliosides. Therefore, glycosylation in breast cancer cells plays an important role in the anticancer activity of ABPs, which may partly explain their cancer-selective toxicity. Anticancer ABPs with cancer-selective cytotoxicity will be promising candidates for anticancer therapy in the future.