Ryan Wood

First-in-human trial of nanoelectroablation therapy for basal cell carcinoma: proof of method.

This nanoelectroablation therapy effectively treats subdermal murine allograft tumors, autochthonous basal cell carcinoma (BCC) tumors in Ptch1+/‐K14‐Cre‐ER p53 fl/fl mice, and UV‐induced melanomas in C57/BL6 HGF/SF mice. Here, we described the first human trial of this modality. We treated 10 BCCs on three subjects with 100–1000 electric pulses 100 ns in duration, 30 kV/cm in amplitude, applied at 2 pulses per second. Seven of the 10 treated lesions were completely free of basaloid cells when biopsied and two partially regressed. Two of the 7 exhibited seborrheic keratosis in the absence of basaloid cells. One of the 10 treated lesions recurred by week 10 and histologically had the appearance of a squamous cell carcinoma. No scars were visible at the healed sites of any of the successfully ablated lesions. One hundred pulses were sufficient for complete ablation of BCCs with a single, 1‐min nanoelectroablation treatment.

Strain in GaAs quantum wells and layered composites detected by optically pumped NMR(Conference Presentation)

We present a methodology for characterizing lattice strain effects in crystalline semiconductors based on optically pumped NMR (OPNMR). Lattice strain is detected as an electric quadrupole splitting of the NMR transition. Since OPNMR is an optical technique, it selectively probes strain only in the volume within the optical penetration depth of the laser light. The methodology is demonstrated in (1) variably thinned bulk GaAs layered composites and (2) GaAs quantum well thin films. Thermally induced lattice strain was induced by epoxy-bonding to Si support wafers at 373 K followed by cooling to 1.5 K. The variation of the strain with GaAs layer thickness is shown to be consistent with an analytical model for mechanical bowing. In the GaAs/AlxGa1-xAs thin films, the strain measured from the quadrupole splitting of the 71Ga NMR transition was incorporated into electronic energy band structure calculations which yield the photon energy dependence of the optical absorption and conduction electron spin polarization. The nuclear spin polarization is calculated from the electron spin polarization using an appropriate electron-nuclear cross-relaxation model. Comparison of theory to the experimental data provides new insights into how the optically pumped nuclear spin polarization is affected by strain and quantum confinement. [1] M. Sturge, Phys. Rev. 127, 768 (1962) [2] Y. Sun, et. al., Strain Effects in Semiconductors: Theory and Device Applications (Springer, 2010). [3] P.L. Kuhns et al., Phys. Rev. B. 55, 7824-7830 (1997). [4] R.M. Wood et al., Phys. Rev. B. 90, 155317 (2014)

Characterization of elastic interactions in GaAs/Si composites by optically pumped nuclear magnetic resonance

Elastic interactions in GaAs/Si bilayer composite structures were studied by optically pumped nuclear magnetic resonance (OPNMR). The composites were fabricated by epoxy bonding of a single crystal of GaAs to a single crystal of Si at 373 K followed by selective chemical etching of the GaAs at room temperature to obtain a series of samples with GaAs thickness varying from 37 μm to 635 μm, while the Si support thickness remained fixed at 650 μm. Upon cooling to below 10 K, a biaxial tensile stress developed in the GaAs film due to differential thermal contraction. The strain perpendicular to the plane of the bilayer and localized near the surface of the GaAs was deduced from the quadrupolar splitting of the Gallium-71 OPNMR resonance. Strain relaxation by bowing of the composite was observed to an extent that depended on the relative thickness of the GaAs and Si layers. The variation of the strain with GaAs layer thickness was found to be in good agreement with a general analytical model for the elastic relationships in composite media.

Modeling optically pumped NMR and spin polarization in GaAs/AlGaAs quantum wells

Optically-pumped nuclear magnetic resonance (OPNMR) spectroscopy is an emerging technique to probe electronic and nuclear spin properties in bulk and quantum well semiconductors. In OPNMR, one uses optical pumping with light to create spin-polarized electrons in a semiconductor. The electron spin can be transferred to the nuclear spin bath through the Fermi contact hyperfine interaction which can then be detected by conventional NMR. The resulting NMR signal can be enhanced four to five orders of magnitude or more over the thermal equilibrium signal. In previous work, we studied OPNMR in bulk GaAs where we investigated the strength of the OPNMR signal as a function of the pump laser frequency. This allowed us to study the spin-split valence band. Here we report on OPNMR studies in GaAs/AlGaAs quantum wells. We focus on theoretical calculations for the average electron spin polarization at different photon energies for different values of external magnetic field in both unstrained and strained quantum wells. Our calculations allow us to identify the Landau level transitions which are responsible for the peaks in the photon energy dependence of the OPNMR signal intensity. The calculations are based on the 8- band Pidgeon-Brown model generalized to include the effects of the quantum confinement potential as well as pseudomorphic strain at the interfaces. Optical properties are calculated within the golden rule approximation. Detailed comparison to experiment allows one to accurately determine valence band spin splitting in the quantum wells including the effects of strain.

Nanoelectroablation for human carcinoma therapy

The use of nanosecond pulsed electric fields to ablate tumors (nanoelectroablation) is now well established in the murine xenograft model system. In order bring this therapy into the clinic for the treatment of human tumors we are developing both a pulse generator as well as delivery electrodes to target the tumors to be treated. We will describe the PulseCure® Model MBR-1 100 ns pulse generator and the first human clinical trial data using nanoelectroablation to scarlessly ablate basal cell carcinomas.