Novel chitosan/gold-MPA nanocomposite for sequence-specific oligonucleotide detection

A 20-mer single-stranded oligodeoxyribonucleotide (ssODNs) was covalently probed onto the nanocomposite electrode, made up of an indium-tin oxide (ITO) glass surface coated with chitosan (CHIT), which is bonded with carboxyl functionalized thiol capped gold nanoparticles (gold-mercaptopropionic acid, Au-MPA NPs). The prepared CHIT/Au-MPA/ITO and the ssODNs/CHIT/Au-MPA/ITO electrodes were characterized with FTIR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). TEM micrograph of the composite electrode showed that Au-MPA NPs had the diameter ranging from 4 to 16 nm. The ssODNs/CHIT/Au-MPA/ITO electrode showed a linear increase in the amperometric current with an increasing concentration of the single-stranded target complementary ODNs (cODNs) within the range of 0.03–325 fM. The ssODNs/CHIT/Au-MPA/ITO electrode exhibited a sensitivity of 0.572 μA/fM with a response time of 12 s. The ssODNs/CHIT/Au-MPA/ITO electrode had a shelf life of ∼182 days, when stored at 4 °C.