ORIGINAL PAPER Individually addressable microelectrode array for monitoring oxygen and nitric oxide release Bhavik Anil Patel & Martin Arundell & Ruben G. W. Quek & Severin L. R. Harvey & Ian R. Ellis & Margaret M. Florence & Anthony E. G. Cass & Ana M. Schor & Danny O’Hare Received: 10 October 2007 / Revised: 7 December 2007 / Accepted: 12 December 2007 / Published online: 10 January 2008 # Springer-Verlag 2007 Abstract We have fabricated a six individual addressable gold working electrode microarray. The device is wire- bonded to an eight-pin DIL package that can be easily interconnected to an external multi-channel potentiostat. A polyion complex film coating on the electrode surface provides a suitable coating for the growth of cells. The responses of oxygen and nitric oxide were assessed on uncoated and coated devices using electroanalytical meth- ods. The film coating reduced the diffusion current by approximately 20% in both cases. No changes in the electrochemical mechanism were observed. Simultaneous recordings were obtained for 2 h in the presence of the cells, thus the device is stable for the duration of the bioan- alytical measurements. Measurements were conducted to study the simultaneous changes in oxygen and nitric oxide levels in cultured fibroblast cells in the presence of growth hormones that cause cell proliferation. Increases in oxygen consumption of the cells were coupled with increases in nitric oxide levels when in the presence of the growth hormones. Use of a biological detergent to cause an oxidative burst resulted in a large increase in the current for potentials set to detect nitric oxide and oxygen. Keywords Microelectrode array . Nitric oxide . Oxygen . Fibroblast cell . Film coating Introduction Over the past 30 years, since the development of integrated circuit fabrication technologies, electrochemical arrays have gained increased popularity due to their ability to analyse several samples simultaneously [1–3]. They are able to measure analytes of interest directly in a complex matrix without the need for laborious sampling or separation techniques. In addition these types of sensor are applicable to a large number of analytical fields including environ- mental analysis, food analysis, and clinical analysis [1]. Microarrays are more compatible with applications where good spatial resolution is required (measurements on the level of the single cell) and where simultaneous monitoring is advantageous [4]. This is especially the case in the field of biomedical sciences where there is a great demand for robust multi-array sensors that are able to operate in biological environments over long periods of time without any sample pre-treatment. In addition, miniaturised electro- chemical electrode arrays have the advantage of increased mass transport due to radial diffusion, which results in faster responses. The smaller electrode areas reduce the double- layer capacitance and the very small current flow reduces Anal Bioanal Chem (2008) 390:1379–1387 DOI 10.1007/s00216-007-1803-0 M. Arundell Laboratori Nanobioenginyeria, Parc Cientific de Barcelona, Campus Diagonal, Universiti de Barcelona, Baldiri Reixac, 10-12, 08028 Barcelona, Spain e-mail: marundell@pcb.ub.es B. A. Patel (*) : M. Arundell : R. G. W. Quek : S. L. R. Harvey : D. O’Hare Department of Bioengineering, Imperial College London, London SW7 2AZ, UK e-mail: bhavik.a.patel@imperial.ac.uk I. R. Ellis : M. M. Florence : A. M. Schor Unit of Cell and Molecular Biology, The Dental School, University of Dundee, Dundee DD1 4HR Scotland, UK A. E. G. Cass Institute of Biomedical Engineering, Imperial College London, London SW7 2AZ, UK (*)