@article{berg_pearce_rohrbaugh_jiang_nolan_ivanisevic_2017, title={Gallium containing composites as a tunable material to understand neuronal behavior under variable stiffness and radiation conditions}, volume={71}, ISSN={["1873-0191"]}, DOI={10.1016/j.msec.2016.10.022}, abstractNote={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.}, journal={MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS}, author={Berg, Nora G. and Pearce, Brady L. and Rohrbaugh, Nathaniel and Jiang, Lin and Nolan, Michael W. and Ivanisevic, Albena}, year={2017}, month={Feb}, pages={317–321} }
 @article{rohrbaugh_hernandez-balderrama_kaess_kirste_collazo_ivanisevic_2016, title={HgNO3 sensitivity of AlGaN/GaN field effect transistors functionalized with phytochelating peptides}, volume={6}, ISSN={["2158-3226"]}, DOI={10.1063/1.4953806}, abstractNote={This study examined the conductance sensitivity of AlGaN/GaN field effect transistors in response to varying Hg/HNO3 solutions. FET surfaces were covalently functionalized with phytochelatin-5 peptides in order to detect Hg in solution. Results showed a resilience of peptide-AlGaN/GaN bonds in the presence of strong HNO3 aliquots, with significant degradation in FET ID signal. However, devices showed strong and varied response to Hg concentrations of 1, 10, 100, and 1000 ppm. The gathered statistically significant results indicate that peptide terminated AlGaN/GaN devices are capable of differentiating between Hg solutions and demonstrate device sensitivity.}, number={6}, journal={AIP ADVANCES}, author={Rohrbaugh, Nathaniel and Hernandez-Balderrama, Luis and Kaess, Felix and Kirste, Ronny and Collazo, Ramon and Ivanisevic, Albena}, year={2016}, 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{kirste_rohrbaugh_bryan_bryan_collazo_ivanisevic_2015, title={Electronic Biosensors Based on III-Nitride Semiconductors}, volume={8}, ISSN={["1936-1327"]}, DOI={10.1146/annurev-anchem-071114-040247}, abstractNote={ We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors. }, journal={ANNUAL REVIEW OF ANALYTICAL CHEMISTRY, VOL 8}, author={Kirste, Ronny and Rohrbaugh, Nathaniel and Bryan, Isaac and Bryan, Zachary and Collazo, Ramon and Ivanisevic, Albena}, year={2015}, pages={149–169} }
 @article{rohrbaugh_bryan_bryan_collazo_ivanisevic_2015, title={Long-term stability assessment of AlGaN/GaN field effect transistors modified with peptides: Device characteristics vs. surface properties}, volume={5}, ISSN={["2158-3226"]}, DOI={10.1063/1.4930192}, abstractNote={AlGaN/GaN Field Effect Transistors (FETs) are promising biosensing devices. Functionalization of these devices is explored in this study using an in situ approach with phosphoric acid etchant and a phosphonic acid derivative. Devices are terminated on peptides and soaked in water for up to 168 hrs to examine FETs for both device responses and surface chemistry changes. Measurements demonstrated threshold voltage shifting after the functionalization and soaking processes, but demonstrated stable FET behavior throughout. X-ray photoelectron spectroscopy and atomic force microscopy confirmed peptides attachment to device surfaces before and after water soaking. Results of this work point to the stability of peptide coated functionalized AlGaN/GaN devices in solution and support further research of these devices as disposable, long term, in situ biosensors.}, number={9}, journal={AIP ADVANCES}, author={Rohrbaugh, Nathaniel and Bryan, Isaac and Bryan, Zachary and Collazo, Ramon and Ivanisevic, Albena}, year={2015}, month={Sep} }
 @article{rohrbaugh_bryan_bryan_arellano_collazo_ivanisevic_2014, title={AlGaN/GaN field effect transistors functionalized with recognition peptides}, volume={105}, number={13}, journal={Applied Physics Letters}, author={Rohrbaugh, N. and Bryan, I. and Bryan, Z. and Arellano, C. and Collazo, R. and Ivanisevic, A.}, year={2014} }
 @article{rohrbaugh_bryan_bryan_collazo_ivanisevic_2014, title={Effects of Environmental Exposure on Stability and Conductance Poly-l-lysine Coated AlGaN/GaN High Electron Mobility Transistors}, volume={61}, ISSN={["1938-6737"]}, DOI={10.1149/06104.0147ecst}, abstractNote={AlGaN/GaN HEMTs have been shown promise to be used as in-situ biosensors. An inquiry was done into the stability of physisorption as a method of adhering surface bioactive molecules to the surface of the HEMT gate contacts. Poly-l-lysine (30,000 MW) was used to coat AlGaN/GaN field effect transistors as a representative charged biomolecule for biosensing applications. Coated FETs were then exposed to 1 and 4 hour soaks in DI water at ambient temperature. Atomic force microscopy (AFM) and conductance measurements (IV) were used to quantify current decay and surface morphology changes. Analysis of the results showed that charged analytes readily adsorbed onto the surface.  Upon adsorption an immediate signal decay was observed. The changes after soaking in solution were variable.  The results point to the need to develop specific chemistry that will result in stable immobilization of biomolecules onto the device surface.  Such stability is necessary for long- term reliable device operation.}, number={4}, journal={WIDE BANDGAP SEMICONDUCTOR MATERIALS AND DEVICES 15}, author={Rohrbaugh, N. and Bryan, I. and Bryan, Z. and Collazo, R. and Ivanisevic, A.}, year={2014}, pages={147–151} }