An electrochemical DNA biosensor developed on novel multinuclear nickel(II) salicylaldimine metallodendrimer platform

An electrochemical DNA biosensor (EDB) was prepared using an oligonucleotide of 21 bases with sequence NH2-5′-GAGGAGTTGGGGGAGCACATT-3′ (probe DNA) immobilized on a novel multinuclear nickel(II) salicylaldimine metallodendrimer on glassy carbon electrode (GCE). The metallodendrimer was synthesized from amino functionalized polypropylene imine dendrimer, DAB-(NH2)8. The EDB was prepared by depositing probe DNA on a dendrimer-modified GCE surface and left to immobilize for 1 h. Voltammetric and electrochemical impedance spectroscopic (EIS) studies were carried out to characterize the novel metallodendrimer, the EDB and its hybridization response in PBS using [Fe(CN)6]3−/4− as a redox probe at pH 7.2. The metallodendrimer was electroactive in PBS with two reversible redox couples at E°′ = +200 mV and E°′ = +434 mV; catalytic by reducing the Epa of [Fe(CN)6]3−/4− by 22 mV; conducting and has diffusion coefficient of 8.597 × 10−8 cm2 s−1. From the EIS circuit fitting results, the EDB responded to 5 nM target DNA by exhibiting a decrease in charge transfer resistance (Rct) in PBS and increase in Rct in [Fe(CN)6]3−/4− redox probe; while in voltammetry, increase in peak anodic current was observed in PBS after hybridization, thus giving the EDB a dual probe advantage.