@article{snyder_davis_berg_pearce_romanyuk_jiricek_paskova_ivanisevic_2019, title={Passivation of semipolar (10-1-1) GaN with different organic adsorbates}, volume={236}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2018.10.109}, abstractNote={Expanding the functionality of electronic materials is often reliant on the attachment of organic molecules to the surface. In this study, several methods for passivating the surface of semipolar (10-1-1) GaN with different chemistries were examined; this included simple physisorption, in-situ functionalization using phosphonic acids, and a two-step carboxylic acid attachment with a peroxide pretreatment. The binding of a variety of different organic adsorbates on semipolar substrates was quantified using X-ray photoelectron spectroscopy (XPS). Our results confirm binding at the organic-inorganic interface through the presence of amine/amide species on the surface. The wide variety of organic molecules, and their binding to inorganic electronic materials, can be exploited to impart specific functionalities in technologies spanning fields of energy, biomedical science, and chemical sensing.}, journal={MATERIALS LETTERS}, author={Snyder, Patrick J. and Davis, Hailey and Berg, Nora G. and Pearce, Brady and Romanyuk, Oleksandr and Jiricek, Petr and Paskova, Tania and Ivanisevic, Albena}, year={2019}, month={Feb}, pages={201–204} }
 @article{snyder_reddy_kirste_lajeunesse_collazo_ivanisevic_2018, title={Variably doped nanostructured gallium nitride surfaces can serve as biointerfaces for neurotypic PC12 cells and alter their behavior}, volume={8}, ISSN={["2046-2069"]}, DOI={10.1039/c8ra06836d}, abstractNote={Neurotypic PC12 cells behavior was studied on nanostructured GaN and rationalized with respect to surface charge, doping level, and chemical functionalization. The semiconductor analysis included atomic force microscopy, Kelvin probe force microscopy, and X-ray photoelectron spectroscopy. The semiconductor surfaces were then evaluated as biointerfaces, and the in vitro cell behavior was quantified based on cell viability, reactive oxygen species production, as well as time dependent intracellular Ca concentration, [Ca2+]i, a known cell-signaling molecule. In this work, we show that persistent photoconductivity (PPC) can be used to alter the surface properties prior to chemical functionalization, the concentration of dopants can have some effect on cellular behavior, and that chemical functionalization changes the surface potential before and after exposure to UV light. Finally, we describe some competing mechanisms of PPC-induced [Ca2+]i changes, and how researchers looking to control cell behavior non-invasively can consider PPC as a useful control knob.}, number={64}, journal={RSC ADVANCES}, author={Snyder, Patrick J. and Reddy, Pramod and Kirste, Ronny and LaJeunesse, Dennis R. and Collazo, Ramon and Ivanisevic, Albena}, year={2018}, pages={36722–36730} }
 @article{snyder_kirste_collazo_ivanisevic_2017, title={Persistent Photoconductivity, Nanoscale Topography, and Chemical Functionalization Can Collectively Influence the Behavior of PC12 Cells on Wide Bandgap Semiconductor Surfaces}, volume={13}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201700481}, abstractNote={Wide bandgap semiconductors such as gallium nitride (GaN) exhibit persistent photoconductivity properties. The incorporation of this asset into the fabrication of a unique biointerface is presented. Templates with lithographically defined regions with controlled roughness are generated during the semiconductor growth process. Template surface functional groups are varied using a benchtop surface functionalization procedure. The conductivity of the template is altered by exposure to UV light and the behavior of PC12 cells is mapped under different substrate conductivity. The pattern size and roughness are combined with surface chemistry to change the adhesion of PC12 cells when the GaN is made more conductive after UV light exposure. Furthermore, during neurite outgrowth, surface chemistry and initial conductivity difference are used to facilitate the extension to smoother areas on the GaN surface. These results can be utilized for unique bioelectronics interfaces to probe and control cellular behavior.}, number={24}, journal={SMALL}, author={Snyder, Patrick J. and Kirste, Ronny and Collazo, Ramon and Ivanisevic, Albena}, year={2017}, month={Jun} }
 @article{berg_pearce_snyder_rohrbaugh_nolan_adhikari_khan_ivanisevic_2016, title={Interfaces with Tunable Mechanical and Radiosensitizing Properties}, volume={8}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.5b11639}, abstractNote={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.}, number={34}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Berg, Nora G. and Pearce, Brady L. and Snyder, Patrick J. and Rohrbaugh, Nathaniel and Nolan, Michael W. and Adhikari, Prajesh and Khan, Saad A. and Ivanisevic, Albena}, year={2016}, month={Aug}, pages={21956–21961} }
 @article{snyder_kirste_collazoa_ivanisevic_2016, title={Nanoscale topography, semiconductor polarity and surface functionalization: additive and cooperative effects on PC12 cell behavior}, volume={6}, ISSN={["2046-2069"]}, DOI={10.1039/c6ra21936e}, abstractNote={This work compares the behavior of PC12 cells on planar and patterned III-nitride materials with nanostructured topographies. Three different materials' compositions containing N-polar and Ga-polar areas are studied: Al0.8Ga0.2N, Al0.7Ga0.3N, and GaN. Surface microscopy and spectroscopy, along with biological assays are used to understand the connection between nanoscopic features, polarity and surface functionalization. All materials are modified using a solution based approach to change their surface composition. The results demonstrate that altering the surface hydrophobicity can be used to generate additive effects with respect to protein adsorption in addition to the cooperative effects observed with respect to planes' polarity and topography. The work also details differences in the release of metal ions from clean and functionalized nanostructured III-polar and N-polar semiconductors in cell culture media, and their relationship to changes in cell response through quantification of cell viability and the production of reactive oxygen species. Our results demonstrate that nanoscale topography can be linked to additional parameters at the cell-semiconductor interface in order to understand and modulate PC12 cell behavior.}, number={100}, journal={RSC ADVANCES}, author={Snyder, Patrick J. and Kirste, Ronny and Collazoa, Ramon and Ivanisevic, Albena}, year={2016}, pages={97873–97881} }