Pharmacokinetics of BPA in gliomas with ultrasound induced blood-brain barrier disruption as measured by microdialysis.

The blood-brain barrier (BBB) can be transiently disrupted by focused ultrasound (FUS) in the presence of microbubbles for targeted drug delivery. Previous studies have illustrated the pharmacokinetics of drug delivery across the BBB after sonication using indirect visualization techniques. In this study, we investigated the in vivo extracellular kinetics of boronophenylalanine-fructose (BPA-f) in glioma-bearing rats with FUS-induced BBB disruption by microdialysis. After simultaneous intravenous administration of BPA and FUS exposure, the boron concentration in the treated brains was quantified by inductively coupled plasma mass spectroscopy. With FUS, the mean peak concentration of BPA-f in the glioma dialysate was 3.6 times greater than without FUS, and the area under the concentration-time curve was 2.1 times greater. This study demonstrates that intracerebral microdialysis can be used to assess local BBB transport profiles of drugs in a sonicated site. Applying microdialysis to the study of metabolism and pharmacokinetics is useful for obtaining selective information within a specific brain site after FUS-induced BBB disruption.

Model analysis of temperature dependence of abnormal resistivity of a multiwalled carbon nanotube interconnection.

A homemade microwave plasma-enhanced chemical vapor deposition method was used to grow a multiwalled carbon nanotube between two nickel catalyst electrodes. To investigate the transport properties and electron scattering mechanism of this interconnection (of approximately fixed length and fixed diameter), we carried out a model analysis of temperature dependence of resistivity. To explain the abnormal behavior of the negative temperature coefficient of resistivity in our experimental results, we then employed theories, such as hopping conductivity theory and variable range hopping conductivity theory, to describe resistivity in the high- and low-temperature ranges, respectively. Further, the grain boundary scattering model is also provided to fit the entire measured curve of temperature dependence of resistivity.

Magnetic properties of multi-walled carbon nanotubes.

The magnetic properties of multiwall carbon nanotubes (MWCNTs) grown by microwave plasma enhanced chemical vapor deposition (MPECVD) were studied by electron paramagnetic resonance and magnetization measurements. The ferromagnetic characters of virgin grown MWCNTs are mainly attributed to the catalyst nanoparticles embedded on the tips. After acid etching for purification, the trace of magnetic resonance prominently distributed from the remnant of catalyst nanoparticles within the lower sectional parts of the tubes and partially might come from the unpaired spins of CNTs. The free radicals from the unbounded carbons and the itinerant conduction electrons of metallic CNTs also contribute to the electron spin resonance. Magnetization measured by a superconducting quantum interference device (SQUID) reveals fairly a small hysteretic loop with small coercive field for both virgin and purified MWCNTs.

Electrical conductance in a single carbon nanofiber.

A microwave-plasma enhanced chemical-vapor-deposition (MPECVD) method was used to grow a solo multi-wall carbon nanofiber, which plays as a bridge across nickel electrodes that were separated by the photolithographic process. The length and diameter of carbon nanofiber are 3 microm and 100 nm, respectively. The single wire across the electrodes reveals a step current-voltage characteristic measured at high currents and low temperatures while shows a continuous behavior for multiple nanofibers. This stepwise conductance can be successfully dwelled by the quasi one-dimensional transport theory of conductors without considering the electron-phonon interaction at low temperatures and is expected to play a crucial role to determine the electrical behavior of these nanodevices.