Incorporation of Nafion (R) pre-coat layers (Nafion (R) (1/2) and Nafion (R) (2/1)), and poly-o-phenylenediamine (PPD) on platinum disk electrodes (127 mu m) for the electrochemical detection of nitric oxide (NO) is discussed. The extensive in vitro development and characterisation of Nafion (R) (1/2) PPD and Nafion (R) (2/1) PPD modified sensors demonstrated excellent sensitivity towards NO (1070 +/- 19 pA mu M-1, n =38 and 990 +/- 14 pA mu M-1, n = 38) respectively which were both significantly different from bare Pt electrodes (352 +/- 25 pA mu M-1, n = 14). There was negligible interference, <1% of the overall signal, from the various electroactive interferents investigated at their respective physiological concentrations. The Nafion (R) (1/2) PPD sensor demonstrated a response time of 18 +/- 2s, n = 38 at 25 degrees C which decreased to 14 +/- 1 s, n = 6 at 37 degrees C with no significant increase in sensitivity observed (1287 +/- 48 pA mu M-1, n = 6). Similarly the Nafion (R) (2/1) PPD sensor demonstrated a response time of 16 +/- 2 s, n =38 at 25 degrees C which decreased to 10 +/- 1 s, n = 6 at 37 degrees C with a non significant decrease in sensitivity observed (791 +/- 41 pA mu M-1, n = 6). The limit of detection was 8 +/- 1 nM, n = 12 for the Nafion (R) (1/2) PPD modified sensor and 7 +/- 1 nM, n = 12 for the Nafion (R) (2/1) PPD modified sensor. Sensocompatibility studies undertaken in proteins (BSA), lipids (PEA) and brain tissue for 28 days resulted in an AA current which is ca. <1% of the bare Pt response (37 +/- 1 nA mM(-1), n = 14). Shelf-life studies for both the Nafion (R) (1/2) PPD and Nafion (R) (2/1) PPD modified sensors demonstrated negligible differences after 56 days storage at 4 degrees C. (C) 2014 Elsevier B.V. All rights reserved.