Magnetically Triggered Release of Entrapped Bioactive Proteins from Thermally Responsive Polymer-Coated Iron Oxide Nanoparticles for Stem-Cell Proliferation.

Nanoparticles could conceal bioactive proteins during therapeutic delivery, avoiding side effects. Superparamagnetic iron oxide nanoparticles (SPIONs) coated with a temperature-sensitive polymer were tested for protein release. We show that coated SPIONs can entrap test proteins and release them in a temperature-controlled manner in a biological system. Magnetically heating SPIONs triggered protein release at bulk solution temperatures below the polymer transition. The entrapped growth factor Wnt3a was inactive until magnetically triggered release, upon which it could increase mesenchymal stem cell proliferation. Once the polymer transition will be chemically adjusted above body temperature, this system could be used for targeted cell stimulation in model animals and humans.

Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves.

The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET.