An electrochemical detection of metallothioneins at the zeptomole level in nanolitre volumes

We report on improvement of the adsorptive transfer stripping technique ( AdTS) coupled with the differential pulse voltammetry Brdicka reaction to determine a thiol-protein. The current technique has been unable to generate reproducible results when analyzing very low sample volumes ( nanolitres). This obstacle can be overcome technically by modifying the current transfer technique including cooling step of the adsorbed analyte. We tested the technique on determination of a promising tumour disease marker protein called metallothionein ( MT). The detection limit ( 3 S/ N) of MT was evaluated as 500 zeptomoles per 500 nL ( 1 pM) and the quantification limit ( 10 S/ N) as 1,500 zeptomoles per 500 nL ( 3 pM). Further, the improved AdTS technique was utilized to analyze blood serum samples from patients with breast cancer. Based on the results obtained it can be concluded that the improved technique can be used to detect a thiol-protein in very low sample volumes and can also prevent interferences during the washing and transferring step.