Loading of silicon nanoparticle labels with redox mediators for detection of multiple DNA targets within a single voltammetric sweep

We have constructed electrochemical labels by loading four different redox mediators into silica nanoparticles (SiNPs) through electrostatic attraction. The mediators were methylene blue, ferrocinium tetrafluoroborate, tris (2,2-bipyridyl) dichlororuthenium (II) hexahydrate and acridine orange. The SiNPs were coated with avidin, which enabled attachment to biotin-tagged DNA sequences, forming signal probes. The immobilisation of four different capture probes onto screen printed electrodes enabled a simple qualitative and semi-quantitative detection of four different target probes within a single voltammetric sweep using differential pulse voltammetry. This was illustrated by detecting sequences found in four forms of the influenza virus, the influenza A sub-types H1N1, H3N2, H5N1 and influenza B. The limits of detection were 1.6 pM, 1.6 pM, 4.7 pM and 2.9 pM, respectively.