Gallium containing composites as a tunable material to understand neuronal behavior under variable stiffness and radiation conditions.

We report a composite biomaterial containing nanostructured GaOOH and Matrigel™ that can be modulated with respect to its stiffness and radiosensitization properties. A variety of concentrations of GaOOH were added to the composite to alter the mechanical properties of the material as well as to tune the radiosensitizing properties to the composite. PC-12 cells were used to study the combined effects of different stimuli on cell behavior. NGF was given to the cells to record their morphology as well as viability. An increase in the substrate stiffness caused an increase in neurite outgrowth but a decrease in cell viability. In addition, increasing the radiation dose decreased neurite outgrowth but increased cell viability when radiosensitizing particles were present. A subtractive effect between radiosensitizing and mechanical stimuli was observed when PC-12 cells were grown on the GaOOH containing composite.

In situ and ex situ functionalization of nanostructured gallium oxy-hydroxide with a porphyrin dye.

The surface attachment of a porphyrin dye to nanocrystalline GaOOH was performed using two routes of solution-based functionalization. The first method of functionalization utilized an in situ incorporation of dissolved porphyrin salt in solution during the microwave synthesis step. Additionally, synthesized GaOOH nanorods were mixed in porphyrin solution after the microwave process to make an ex situ GaOOH/TTP-PO-3 . X-ray photoelectron spectroscopy confirmed the presence of expected surface species and provided evidence of increased surface coverage of TTP-PO3 on GaOOH in the ex situ- GaOOH/TTP-PO3 as compared to the in situ one. Size and morphology changes were investigated using SEM and, along with analysis of XRD, the in situ samples showed larger crystallite sizes. This was confirmed with PL due to the higher bandgap energy evident in the ex situ GaOOH/TTP-PO3 compared to the in situ sample. A stability study was performed using fluorescence spectroscopy which indicated no leaching of porphyrin from the in situ GaOOH/TTP-PO3 . However, porphyrin leaching was evident from the ex situ GaOOH/TTP-PO3 sample. The stability of the in situ GaOOH/TTP-PO3 makes it attractive for a number of interfacial applications. SCANNING 38:671-683, 2016. © 2016 Wiley Periodicals, Inc.

Interfaces with Tunable Mechanical and Radiosensitizing Properties.

We report the fabrication of a composite containing nanostructured GaOOH and Matrigel with tunable radiosensitizing and stiffness properties. Composite characterization was done with microscopy and rheology. The utility of the interface was tested in vitro using fibroblasts. Cell viability and reactive oxygen species assays quantified the effects of radiation dosages and GaOOH concentrations. Fibroblasts' viability decreased with increasing concentration of GaOOH and composite stiffness. During ionizing radiation experiments the presence of the scintillating GaOOH triggered a different cellular response. Reactive oxygen species data demonstrated that one can reduce the amount of radiation needed to modulate the behavior of cells on interfaces with different stiffness containing a radiosensitizing material.

Surface characterization of gallium nitride modified with peptides before and after exposure to ionizing radiation in solution.

An aqueous surface modification of gallium nitride was employed to attach biomolecules to the surface. The modification was a simple two-step process using a single linker molecule and mild temperatures. The presence of the peptide on the surface was confirmed with X-ray photoelectron spectroscopy. Subsequently, the samples were placed in water baths and exposed to ionizing radiation to examine the effects of the radiation on the material in an environment similar to the body. Surface analysis confirmed degradation of the surface of GaN after radiation exposure in water; however, the peptide molecules successfully remained on the surface following exposure to ionizing radiation. We hypothesize that during radiation exposure of the samples, the radiolysis of water produces peroxide and other reactive species on the sample surface. Peroxide exposure promotes the formation of a more stable layer of gallium oxyhydroxide which passivates the surface better than other oxide species.