M.B. Wayu, M.A. Schwarzmann, S.D. Gillespie, M.C. Leopold
University of Richmond,
Keywords: carbon nanotubes, cyclodextrin, uric acid
Summary:Strategies involving carbon nanotube material for the selective, sensitive, and cost effective measurement of uric acid via an (UA) electrochemical sensor have been investigated. The presence of abnormal levels of UA in biological fluids such as blood and urine are symptomatic of many diseases [1-7], including as a diagnostic marker for pregnancy–induced hypertension (PIH), a condition that can lead to a disorder known as pre–eclampsia which poses significant health risks for both mothers and infants [8, 9]. Emergency cesarean section surgery remains a standard procedure to halt PIH progression even in cases where the condition is only suspected based on hypertension assessment. The cost of cesarean section is increasing, costing us billions of dollars every year. UA has been identified as a reliable marker to predict PIH and prevent both unnecessary surgeries and pre–eclampsia cases [8, 9]. Current UA testing procedures require time–consuming laboratory evaluation of blood/urine  during which the PIH can remain undiagnosed and progress toward pre–eclampsia. Carbon nanotubes (CNT) have been explored as a nanomaterial that can be a functional component of highly sensitive electrochemical sensors. However, the dispersion of CNT in aqueous solvents represents a formidable challenge to employing this material in all of the studies . –cyclodextrin (–CD), owing to its hydrophilic character and natural cavity size, has been employed to selectively sequester UA for electrochemical detection . In this study, various methods such as sonication, electropolymerization, and covalent attachment of –CD are assessed to increase the dispersibility of CNT in aqueous solution for its application in making an amperometric UA electrochemical sensor. The surface morphology and structure of the electrode materials were characterized using transmission electron microscopy (TEM), scanning electron microscope (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR). The analytical performance of the developed electrochemical sensors was assessed from direct UA injection during amperometric analysis and typically exhibited effective detection of UA across clinically relevant ranges (100–700 μM), excellent stability, as well as demonstrated selectivity against various interferents. The overall performance of the developed electrochemical sensors and strategies on UA selectivity/sensitivity are discussed. References  Chauhan N, Pundir CS. Anal. Biochem. 2011, 413, 97-103.  Retna Raj C, Ohsaka T. J. Electroanal. Chem. 2003, 540, 69-77.  Lakshmi D, Whitcombe MJ, Davis F, Sharma PS, Prasad BB. Electroanal. 2011, 23, 305-20.  Moraes ML, Rodrigues Filho UP, Oliveira ON, Ferreira M. J. Solid State Electrochem. 2007, 11, 1489-95.  Wang Z, Wang Y, Luo G. Analyst 2002, 127, 1353-8.  Erden PE, Kaçar C, Öztürk F, Kılıç E. Talanta 2015, 134, 488-95.  Li Y, Ran G, Yi WJ, Luo HQ, Li NB. Microchimica Acta 2012, 178, 115-21.  Roberts JM, Bodnar LM, Lain KY, Hubel CA, Markovic N, Ness RB, Powers RW. Hypertension 2005, 46, 1263-9.  Conway GE, Lambertson RH, Schwarzmann MA, Pannell MJ, Kerins HW, Rubenstein KJ, Dattelbaum JD, Leopold MC. J. Electroanal. Chem. 2016, 775, 135-45.  Hrapovic S, Liu Y, Male KB, Luong JHT. Anal. Chem. 2004, 76, 1083-8.