In this paper, an electrochemical biosensor based on gold and palladium nano particles-modified na-
noporous stainless steel (Au-Pd/NPSS) electrode has been introduced for the simultaneous determination
of levodopa (LD) and uric acid (UA). To prepare the electrode, the stainless steel was anodized to fabricate
NPSS and then Cu was electrodeposited onto the nanoporous steel by applying the multiple step po-
tential. Finally, the electrode was immersed into a gold and palladium precursor's solution by the atomic
ratio of  9:1  to  form  Au-Pd/NPSS through the  galvanic  replacement  reaction. Morphological  aspects,
structural properties and the electroanalytical behavior of the Au-Pd/NPSS electrode were studied using
field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray
diffraction  (XRD),  electrochemical  impedance  spectroscopy  (EIS)  and  voltammetric  techniques.  Also,
differential pulse voltammetry (DPV) was used for the simultaneous determination of LD and UA. Ac-
cording to results, the surface of Au-Pd/NPSS electrode contained Au and Pd nanoparticles with an
average diameter of 75 nm. The electrode acted better than Au/NPSS and Pd/NPSS electrodes for the
simultaneous determination of LD and UA, with the peak separation potential of about 220 mV. Also, the
calibration plot for LD was in two linear concentration ranges of 5.0–10.0 and 10.0–55.0 μ mol L
1
and for UA, it was in the range of 100–1200 μ mol L
1 . The detection limit for LD and UA was 0.2 and 15 μ
mol L
1, respectively. The modified electrode had a good performance for LD and UA detection in urine,
blood serum and levodopa C-Forte tablet.