Person:
Issadore, David

Profile Picture

Email Address

AA Acceptance Date

Birth Date

Research Projects

Organizational Units

Job Title

Last Name

Issadore

First Name

David

Name

Issadore, David
Author's Publications: search.filters.isAuthorOfPublication.31ade247-f899-46d7-a45a-a31dcfccf175

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis
    (Royal Society of Chemistry (RSC), 2013) Koziej, Dorota; Floryan, Caspar Jerzy; Sperling, Ralph A.; Ehrlicher, Allen Joseph; Issadore, David; Westervelt, Robert; Weitz, David
    We describe a microfluidic device with an integrated microwave heater specifically designed to dielectrically heat non-aqueous droplets using time-varying electrical fields with the frequency range between 700 and 900 MHz. The precise control of frequency, power, temperature and duration of the applied field opens up new vistas for experiments not attainable by conventional microwave heating. We use a non-contact temperature measurement system based on fluorescence to directly determine the temperature inside a single droplet. The maximum temperature achieved of the droplets is 50 °C in 15 ms which represents an increase of about 25 °C above the base temperature of the continuous phase. In addition we use an infrared camera to monitor the thermal characteristics of the device allowing us to ensure that heating is exclusively due to the dielectric heating and not due to other effects like non-dielectric losses due to electrode or contact imperfection. This is crucial for illustrating the potential of dielectric heating of benzyl alcohol droplets for the synthesis of metal oxides. We demonstrate the utility of this technology for metal oxide nanoparticle synthesis, achieving crystallization of tungsten oxide nanoparticles and remarkable microstructure, with a reaction time of 64 ms, a substantial improvement over conventional heating methods.
  • Thumbnail Image
    Publication
    Magnetic Nanoparticles and MicroNMR for Diagnostic Applications
    (Ivyspring International Publisher, 2012) Shao, Huilin; Min, Changwook; Issadore, David; Liong, Monty; Yoon, Tae-Jong; Weissleder, Ralph; Lee, Hakho
    Sensitive and quantitative measurements of clinically relevant protein biomarkers, pathogens and cells in biological samples would be invaluable for disease diagnosis, monitoring of malignancy, and for evaluating therapy efficacy. Biosensing strategies using magnetic nanoparticles (MNPs) have recently received considerable attention, since they offer unique advantages over traditional detection methods. Specifically, because biological samples have negligible magnetic background, MNPs can be used to obtain highly sensitive measurements in minimally processed samples. This review focuses on the use of MNPs for in vitro detection of cellular biomarkers based on nuclear magnetic resonance (NMR) effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits MNPs as proximity sensors to modulate the spin-spin relaxation time of water molecules surrounding the molecularly-targeted nanoparticles. With new developments such as more effective MNP biosensors, advanced conjugational strategies, and highly sensitive miniaturized NMR systems, the DMR detection capabilities have been considerably improved. These developments have also enabled parallel and rapid measurements from small sample volumes and on a wide range of targets, including whole cells, proteins, DNA/mRNA, metabolites, drugs, viruses and bacteria. The DMR platform thus makes a robust and easy-to-use sensor system with broad applications in biomedicine, as well as clinical utility in point-of-care settings.
  • Thumbnail Image
    Publication
    Scaling of Transverse Nuclear Magnetic Relaxation due to Magnetic Nanoparticle Aggregation
    (Elsevier, 2010) Brown, Keith A.; Vassiliou, Christophoros C.; Issadore, David; Berezovsky, Jesse; Cima, Michael; Westervelt, Robert
    The aggregation of superparamagnetic iron oxide (SPIO) nanoparticles decreases the transverse nuclear magnetic resonance (NMR) relaxation time \(T_{2}^{CP}\) of adjacent water molecules measured by a Carr-Purcell-Meiboom-Gill (CPMG) pulse-echo sequence. This effect is commonly used to measure the concentrations of a variety of small molecules. We perform extensive Monte Carlo simulations of water diffusing around SPIO nanoparticle aggregates to determine the relationship between \(T_{2}^{CP}\) and details of the aggregate. We find that in the motional averaging regime \(T_{2}^{CP}\) scales as a power law with the number \(N\) of nanoparticles in an aggregate. The specific scaling is dependent on the fractal dimension \(d\) of the aggregates. We find \(T_{2}^{CP} \propto N^{-0.44}\) for aggregates with \(d=2.2\), a value typical of diffusion limited aggregation. We also find that in two-nanoparticle systems, \(T_{2}^{CP}\) is strongly dependent on the orientation of the two nanoparticles relative to the external magnetic field, which implies that it may be possible to sense the orientation of a two-nanoparticle aggregate. To optimize the sensitivity of SPIO nanoparticle sensors, we propose that it is best to have aggregates with few nanoparticles, close together, measured with long pulse-echo times.