Aptamer-based determination of tumor necrosis factor α using a screen-printed graphite electrode modified with gold hexacyanoferrate.

An aptamer based method is presented for the voltammetric determination of human tumor necrosis factor alpha (TNF-α). Layers of gold hexacyanoferrate (AuHCF) and gold nanoparticles (AuNPs) were directly immobilized on a graphite screen-printed electrode (SPE). Through the strong interaction between cyanide ions (CN-) of AuHCF and AuNPs, gold nanoparticles are assembled on the modified SPE, and this allows for the covalent immobilization of thiolated aptamers against TNF-α (TNF-α-Apt). On incubation of the aptasensor with of TNF-α, the Apt/TNF-α complex is formed, and this leads to a hindered electron transfer and to a decrease in the peak current of the redox probe. Under optimum conditions and at a typical working as low as 0.1 V (vs. a silver pseudo electrode), the electrode works in the 10 pg.mL-1 to 40 μg.mL-1 TNF-α concentration range, with a 5.5 pg.mL-1 detection limit. The high sensitivity and wide detection range of this method allowed TNF-α to in human serum be detected even at very low concentrations. Graphical abstract Schematic diagram for fabrication of aptasensor: (a,b) formation of AuHCF film by electrodeposition; (c) assembled AuNPs; (d) TNF-α-aptamer loading; (e) blocking of nonspecific sites with 1-HT; and (f) binding to TNF-α.