Magneto-Mechanical Actuation Induces Endothelial Permeability.

Cancer treatment is one of the major health problems that burden our society. According to the American Cancer Society, over 1.9 million new cancer cases and ∼0.6 million deaths from cancer are expected in the US in 2023. Therapeutic targeting is considered to be the gold standard in cancer treatment. However, when a tumor grows beyond a critical size, its vascular system differentiates abnormally and erratically, creating a heterogeneous endothelial barrier that further restricts drug delivery into tumors. While several methods exist, these prompt tumor migration and the appearance of new metastatic sites. Herein, we propose an innovative method based on magneto-mechanical actuation (MMA) to induce endothelial permeability. This method employs FDA-approved PEGylated superparamagnetic iron oxide nanoparticles (PEG-SPIONs) and alternating nonheating magnetic fields. MMA lies in the translation of magnetic forces into mechanical agitation. As a proof of concept, we developed a 2D cell culture model based on human umbilical vein endothelial cells (HUVEC), which were incubated with PEG-SPIONs and then exposed to different magnetic doses. After adjusting the particle concentration, incubation times, and parameters (amplitude, frequency, and exposure time) of the magnetic field generator, we induced actin filament remodeling and subsequent vascular endothelial-cadherin junction disruption. This led to transient gaps in cell monolayers, through which fluorescein isothiocyanate-dextran was translocated. We observed no cell viability reduction for 3 h of particle incubation up to a concentration of 100 µg/mL in the presence and absence of magnetic fields. For optimal permeability studies, the magnetic field parameters were adjusted to 100 mT, 65 Hz, and 30 min in a pulse mode with 5 min OFF intervals. We found that the endothelial permeability reached the highest value (33%) when 2 h postmagnetic field treatment was used. To explain these findings, a magneto-mechanical transduced stress mechanism mediated by intracellular forces was proposed. This method can open new avenues for targeted drug delivery into anatomic regions within the body for a broad range of disease interventions.

A study of dopant incorporation in Te-doped GaAsSb nanowires using a combination of XPS/UPS, and C-AFM/SKPM.

We report the first study on doping assessment in Te-doped GaAsSb nanowires (NWs) with variation in Gallium Telluride (GaTe) cell temperature, using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), conductive-atomic force microscopy (C-AFM), and scanning Kelvin probe microscopy (SKPM). The NWs were grown using Ga-assisted molecular beam epitaxy with a GaTe captive source as the dopant cell. Te-incorporation in the NWs was associated with a positive shift in the binding energy of the 3d shells of the core constituent elements in doped NWs in the XPS spectra, a lowering of the work function in doped NWs relative to undoped ones from UPS spectra, a significantly higher photoresponse in C-AFM and an increase in surface potential of doped NWs observed in SKPM relative to undoped ones. The carrier concentration of Te-doped GaAsSb NWs determined from UPS spectra are found to be consistent with the values obtained from simulated I-V characteristics. Thus, these surface analytical tools, XPS/UPS and C-AFM/SKPM, that do not require any sample preparation are found to be powerful characterization techniques to analyze the dopant incorporation and carrier density in homogeneously doped NWs.

A study of n-doping in self-catalyzed GaAsSb nanowires using GaTe dopant source and ensemble nanowire near-infrared photodetector.

This work reports a comprehensive investigation of the effect of gallium telluride (GaTe) cell temperature variation (TGaTe) on the morphological, optical, and electrical properties of doped-GaAsSb nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE). These studies led to an optimum doping temperature of 550 °C for the growth of tellurium (Te)-doped GaAsSb NWs with the best optoelectronic and structural properties. Te incorporation resulted in a decrease in the aspect ratio of the NWs causing an increase in the Raman longitudinal optical/transverse optical vibrational mode intensity ratio, large photoluminescence emission with an exponential decay tail on the high energy side, promoting tunnel-assisted current conduction in ensemble NWs and significant photocurrent enhancement in the single nanowire. A Schottky barrier photodetector (PD) using Te-doped ensemble NWs with broad spectral range and a longer wavelength cutoff at ∼1.2 µm was demonstrated. These PDs exhibited responsivity in the range of 580-620 A W-1 and detectivity of 1.2-3.8 × 1012 Jones. The doped GaAsSb NWs have the potential for further improvement, paving the path for high-performance near-infrared (NIR) photodetection applications.