1,721,007 research outputs found
Photonic encryption platform using UV-transparent silicon nitride and vectorial hologram
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The Design Principles and the Experimental Characterization of Electrically Tunable Bifocal Metalens System
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Single step fabrication of nanostructure composed of TiO2 nanoparticle embedded resin using nanoimprint lithography
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Direct Electrochemical Detection of Individual Collisions Between Magnetic Microbead/Silver Nanoparticle Conjugates and a Magnetized Ultramicroelectrode
Get PDFHere, we report on the electrochemical detection of individual collisions between a conjugate consisting of silver nanoparticles (AgNPs) linked to conductive magnetic microbeads (cM mu Bs) via DNA hybridization and a magnetized electrode. The important result is that the presence of the magnetic field increases the flux of the conjugate to the electrode surface, and this in turn increases the collision frequency and improves the limit of detection (20 aM). In addition, the magnitude of the charge associated with the collisions is greatly enhanced in the presence of the magnetic field. The integration of DNA into the detection protocol potentially provides a means for using electrochemical collisions for applications in biological and chemical sensing.U.S. Defense Threat Reduction Agency HDTRA1-11-10005Robert A. Welch Foundation F-0032National Research Foundation of Korea - Ministry of Science, ICT and Future Planning NRF-2014S1A2A2028540Chemistr
Turn-On Fluorescence Sensing of Oxygen with Dendrimer-Encapsulated Platinum Nanoparticles as Tunable Oxidase Mimics for Spatially Resolved Measurement of Oxygen Gradient in a Human Gut-on-a-Chip
No full textTurn-on type fluorescence sensing of O-2 is considered a promising approach to developing ways to measure O-2 in microenvironments with spatially distributed O-2 levels. As a class of nanomaterials with a high degree of control over composition and structure, dendrimer-encapsulated nanoparticles (DENs) are promising candidates to mimic biological enzymes. Here, we report a strategy to monitor spatially distributed O-2 across a three-dimensional (3D) human intestinal epithelial layer in a gut-on-a-chip in a turn-on fluorescence sensing manner. The strategy is based on the oxidase-mimetic activity of Pt DENs for catalytic oxidation of nonfluorescent Amplex Red to highly fluorescent resorufin in the presence of O-2. We synthesized Pt DENs using two different types of dendrimers (i.e., amine- terminated or hydroxyl-terminated generation 6 polyamidoamine (PAMAM) dendrimers) with six different Pt2+/dendrimer ratios (i.e., 55, 200, 220, 550, 880, and 1320). After clarifying the intrinsic oxidase-mimetic activity of Pt DENs, we determined tunable oxidase-mimetic activity of Pt DENs, especially with fine-tuning the ratios of the Pt precursor ions and dendrimers. Particularly, the optimal Pt DENs having a Pt2+/dendrimer ratio of 1320 exhibited an similar to 117-fold increase in the oxidase-mimetic activity for catalyzing the aerobic oxidation of Amplex Red to resorufin compared to one having a Pt2+/dendrimer ratio of 200. This study exemplified a simple yet effective approach for spatially resolved imaging of O-2 using metal nanoparticle-based oxidase mimics in microphysiological environments like a human gut-on-a-chip.
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