N^G-Hydroxy-L-arginine (NOHA) is a suspected biomarker in breast cancer due to its involvement in the L-arginine metabolism [1]. Previous research in human breast cancer cells has shown that NOHA, a potent arginase inhibitor, has an antiproliferative and apoptotic actions on the arginase-expressing cells [1]. NOHA is a stable intermediate product in the production of NO from the consumption of L-arginine [1]. L-ornithine and L-citrulline are also involved in the metabolism of L-arginine through the urea cycle; the urea cycle has been known to be disrupted in cancer patients [1]. Early detection of cancer is important for rapid treatment options to be available [2]. Electrochemical detection is an established, cost-effective method that has potential to detect the onset of cancer because of its ability to successfully detect low levels of analyte concentrations. Before a robust biosensor sensor can be made the characterization of the electrochemical detection of NOHA needs to be done.

Electrochemical activity of NOHA was investigated with cyclic voltammetry and differential pulse voltammetry. NOHA was found to have an oxidation and reduction peak at 355 mV and 188 mV vs. Ag/AgCl respectively. In cyclic voltammetric measurements a scan rate of 50 mVs^-1 was used over the applied potential of -0.2 to 0.6 V vs Ag/AgCl. Triplicate data was obtained for serial dilutions of NOHA in two different buffers; Phosphate Buffer Saline solution pH 7.3 (PBS) and 100uM L-Ornithine, 10uM L-Citrulline, and 100uM L-Arginine in PBS (LOCA). The electrochemical detection of NOHA in a LOCA solution was done to understand the effect of a urea cycle metabolite mixture on electrode fowling and sensitivity. A shift in oxidation peak voltage was found for the LOCA solution by 5 mV to 360 mV. The sensitivity of the NOHA in PBS and LOCA solutions were found to be 5.4 nA/uM and 4.8 nA/uM respectively. In addition to our multiple data points to discuss sensitivity and reproducibility in the detection of NOHA, we will report kinetic information including the number of electrons transferred and diffusivity. We will also discuss our progress to decrease the limit-of-detection of NOHA in an effort to make a more sensitive bioanalyte sensor.

[1] R. Singh, S. Pervin, A. Karimi, S. Cederbaum, and G. Chaudhuri, “Arginase activity in human breast cancer cell lines: N^ω-hydroxy-L-arginine selectively inhibits cell proliferation and induces apoptosis in MDA-MB-468 cells,” Cancer Res., vol. 60, pp. 3305–3312, (2000)

[2] Zhen Zhang, Robert C. Bast, Jr., Yinhua Yu, Jinong Li, Lori J. Sokoll, Alex J. Rai, Jason M. Rosenzweig, Bonnie Cameron, Young Y. Wang, Xiao-Ying Meng, Andrew Berchuck, Carolien van Haaften-Day, and Neville F. Hacker, Henk W. A. de Bruijn, Ate G. J. van der Zee, Ian J. Jacobs, Eric T. Fung, and D. W. Chan, “Three Biomarkers Identified from Serum Proteomic Analysis for the Detection of Early Stage Ovarian Cancer,” Cancer Res., vol. 64, pp. 5882–5890, (2004)