Electrochemical detection of mobile zinc ions for early diagnosis of prostate cancer

We report a highly selective and sensitive electrochemical method for the detection of mobile zinc ions (Zn2+) useful for early diagnosis of prostate cancer. The working electrode on a screen-printed electrode (SPE) was modified with zincon and electrochemically exfoliated graphite complex (zincon-EG) to afford the binding of Zn2+ on zincon-EG/SPE. UV–vis and FT-IR were used to characterize zincon-EG, XRD and SEM for zincon-EG and zincon-EG-enriched with Zn2+, and cyclic voltammogram for binding of Zn2+ at zincon-EG/SPE. The optimal conditions for detecting Zn2+ were with Tris-HCl as an electrolyte (pH 7.5) over 5 min of pre-concentration and applying electrodeposition potential of −1.2 V for 100 s. Differential pulse voltammetry (DPV) was used to establish the calibration curve and the linear range of Zn2+ detection in buffer solutions as 0.25 to 1.5 mg/L. The prepared zincon-EG/SPE sensors show good repeatability (RSD = 6.9%, n = 5) and are stable for over two weeks. Three mouse serum samples derived from transgenic adenocarcinoma of mouse prostate (TRAMP) were used as real matrices for testing by after diluting (500×) and spiking with different amounts of Zn2+ (0.5, 1.0, 2.0, 3.0, 4.0 mg/L) through standard addition. From the DPV data, the original concentrations of mobile Zn2+ in the three serum samples were determined as 50, 41.5 and 5 mg/L. The average Zn2+ detection sensitivity, based on the linear responses obtained with our sensor, is 2.5 mg/L and the limit of detection is 5 μg/L.