Nanostructured platinum modified electrodes were prepared by the electrodeposition of platinum on Nation (Nf) film coated glassy carbon (GC) electrode. Surface characterization such as morphology and chemical state was accomplished by AFM, XPS, and XRD. The nanostructured Pt (represented Pt-nano) deposited on GC (GC/Pt-nano) and GC/Nafion (GC/Nf/Pt-nano) electrodes were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The formation of nanostructured Pt on electrodes was found to be very high at the interior hydrophilic cluster regions of the Nf film. The AFM images of the Pt deposited electrode surface reveal that the clusters of electrodeposited nanostructured Pt consist of a number of nanocrystallites. The surface morphology of the electrodeposited nanostructured Pt was uneven presumably due to the preferential growth of such nanocrystallites in certain crystallographic directions. The high surface area to volume of the nanostructured Pt deposited in Nf film on GC electrode was utilized for efficient electrocatalytic oxidation of neurotransmitter molecules in the presence of interfering species. The present investigation establishes the electrocatalytic oxidation of dopamine and serotonin by GC/Nf/Pt-nano electrodes in the presence of interfering molecules such as ascorbic acid and uric acid. The results were compared with both plain GC and bulk Pt electrodes. Good electronic communication throughout the film was apparent in the GC/Nf/Pt-nano electrode. Rotating disc electrode experiments were carried out to determine the rate constant for the electrocatalytic oxidation of dopamine at the modified electrodes. Under optimal conditions of dopamine oxidation the GC/Nf/Pt-nano electrode exhibits a linear relationship in the range of 3 x 10(-6) -60 x 10(-6) mol dm(-3) with a detection limit down to 1 x 10(-8) mol dm(-3) (10 nM) dopamine. It has been also shown that the GC/Nf/Pt-nano electrode can be used as a biosensor with high selectivity, sensitivity and detection of submicromolar concentrations of dopamine and serotonin with practical applications to real samples. (c) 2005 Elsevier B.V. All rights reserved.