Research Fellow @ Massachusetts Institute of Technology, Transfusion Medicine Fellow @ Dartmouth-Hitchcock Medical Center


Multimodal biomedical imaging with asymmetric single-walled carbon nanotube/iron oxide nanoparticle complexes

Magnetic iron oxide nanoparticles and near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWNT) form heterostructured complexes that can be utilized as multimodal bioimaging agents. Fe catalyst-grown SWNT were individually dispersed in aqueous solution via encapsulation by oligonucleotides with the sequence d(GT)15, and enriched using a 0.5 T magnetic array. The resulting nanotube complexes show distinct NIR fluorescence, Raman scattering, and visible/NIR absorbance features, corresponding to the various nanotube species. AFM and cryo-TEM images show DNA-encapsulated complexes composed of a approximately 3 nm particle attached to a carbon nanotube on one end. X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) measurements reveal that the nanoparticles are primarily Fe2O3 and superparamagnetic. The Fe2O3 particle-enriched nanotube solution has a magnetic particle content of approximately 35 wt %, a magnetization saturation of approximately 56 emu/g, and a magnetic relaxation time scale ratio (T1/T2) of approximately 12. These complexes have a longer spin-spin relaxation time (T2 approximately 164 ms) than typical ferromagnetic particles due to the smaller size of their magnetic component while still retaining SWNT optical signatures. Macrophage cells that engulf the DNA-wrapped complexes were imaged using magnetic resonance imaging (MRI) and NIR mapping, demonstrating that these multifunctional nanostructures could potentially be useful in multimodal biomedical imaging.

Computational Analysis of Transition Metal Doped Nanotubes and Their Application to Molecular Electronics

We have previously proposed molecular circuits designed from polyaniline polymer strands, polyacetylene polymer strands and charge transfer salts acting as transistors. Due to unique properties that are demonstrated in this manuscript, we propose the use of carbon single wall nanotubes and transition metal endohedrally doped single wall carbon nanotubes (SWNTs) for utilization in molecular electronics. Different transition metals were used in a systematic fashion to manipulate the molecular orbital energy gap (HOMO-LUMO gap) of metallic (Ch = (n = m)) nanotubes. Gradient corrected, Density Functional Theory (DFT) Self Consistent Field (SCF) calculations were used to calculate molecular orbital energy levels, HOMO-LUMO gaps, electron affinities, ionization energies and other electronic properties for these molecules. The effect that a SWNT’s length has on its HOMO-LUMO gap was investigated. DFT-SCF calculations were also used to demonstrate how multiple metal filled nanotubes could be used to construct a molecular nanotube based transistor.

Physician-scientist with extensive experience developing and translating nanotechnologies and biomedical optical technologies from the bench to clinic in areas of genetics, oncology, and cardiovascular diseases. Extensive experience in community building in healthcare innovation, research, medical, and physician-scientist communities through various leadership roles.

Research Profiles