Daniel S. Choi

Magnetically driven spinning nanowires as effective materials for eradicating living cells

We present a method to inflame cells, in vitro, by applying an alternating current (ac) magnetic field to ferromagnetic nanowires (NWs) internalized by living cells. Nickel (Ni) NWs were internalized by human embryonic kidney cells (HEK-293). The application of ac magnetic field to the cells induced spinning of the cells via the motion of internalized NWs. This resulted in cell death by physically causing damage. A study of the response of cytokine to cells with spinning NWs shows increased interleukin-6 effects when compared with responses from non-spinning cells. The spinning effect of cells caused by the application of magnetic field can be used to target and inflame the cells. Such experiments suggest the possibility of inflaming cells for the treatment of cancer.

Radio frequency-mediated local thermotherapy for destruction of pancreatic tumors using Ni–Au core–shell nanowires

We present a novel method of radio frequency (RF)-mediated thermotherapy in tumors by remotely heating nickel (Ni)-gold (Au) core-shell nanowires (CSNWs). Ectopic pancreatic tumors were developed in nude mice to evaluate the thermotherapeutic effects on tumor progression. Tumor ablation was produced by RF-mediated thermotherapy via activation of the paramagnetic properties of the Ni-Au CSNWs. Histopathology demonstrated that heat generated by RF irradiation caused significant cellular death with pyknotic nuclei and nuclear fragmentation dispersed throughout the tumors. These preliminary results suggest that thermotherapy ablation induced via RF activation of nanowires provides a potential alternative therapy for cancer treatment.

Reinforcement of Cu nanoink sintered film with extended carbon nanofibers for large deformation of printed electronics

Metallic nanoparticle inks (nanoinks) have attracted great interest in the manufacturing of printed flexible electronics. However, sintering pure nanoinks in ambient conditions results in micro-cracks and pores within the sintered film, which deteriorate the mechanical and electrical characteristics of the sintered nanoinks. To alleviate these problems, we demonstrate the use of very long carbon nanofiber (average length 200 µm) to reinforce the sintered nanoink films. In this study, different weight fractions of carbon nanofiber are dispersed into the Cu nanoink to improve the mechanical bending characteristics. Scanning electron micrographs show improved dispersion of oxidized carbon nanofiber in the nanoink compared to the as-received carbon nanofiber. The composite nanoinks are stencil printed on polyethylene terephthalate film and sintered by intense pulsed light using Xe-flash. The electrical measurements show 90%, 65%, and 66% improved electrical conductivity in the composite nanoink film (0.7% of oxidized carbon nanofiber) compared to the pure Cu nanoink under the 7.5 cm, 5.0 cm, and 2.5 cm of bending radii, respectively.

Dynamic Microcontainers as Microvacuums for Collecting Nanomaterials After Clinical Treatments

We present a feasible method to collect ferromagnetic nanomaterials(FNMs) after clinical utilization by employing ferromagnetic microcontainers (MCs). The cubic MCs with dimensions of 200 micrometers have gold-coated nickel frames and were tethered such a way that they are able to remove FNMs from cells with the use of an external magnetic field. The study has been conducted in two parts: 1) enhancement of the motion of MCs in glass-based microfluidic channels filled with viscous fluids by magnetically-driven spinning MCs, i.e., “dynamic MCs”; 2)sweeping FNMs from the cells using magnetic attractive forces between FNMs and MCs through a “microvacuum”process. Our study shows that spinning MCs can transport better than nonspinning MCs through viscous fluids. We found that approximately 70% of FNMs internalized with human embryonic cells (HEK-293) were removed from the cells by the spinning MCs. Such in-vitro experiments suggest the possibility of resolving the issue of removing FNMs used for clinical treatments from human body after treatments.

In Vitro Detection of Neural Activity with Vertically Grown Single Platinum Nanowire

We present a process for fabricating a nanoscale probing device for in vitro sensing of neural activity. Single vertical platinum (Pt) nanowires were fabricated on a microelectrode array by focused ion beam (FIB) - chemical vapor deposition (CVD) in order to improve the spatial resolution of recording and to minimize damage to the cells. Electrodes in contact with cells detected prominent spontaneous electrical activity. Such small geometry of vertical nanowires may enable probing multiple sites within a cell.