Novel bioelectrochemical assays for the detection of DNA hybridization

The use of DNA testing as an important tool for breast cancer diagnosis has been increased rapidly over the past decade. DNA hybridization electrical biosensors have received great attention because of their high sensitivity, excellent selectivity and many other advantageous features of the electrochemical biosensors.; This research focused on a systematic search for effective electrical devices and protocols for detecting DNA hybridization. The experimental results show that graphite pencil, carbon paste and polypyrrole coated glassy carbon (PPy/GC) electrode surfaces can offer a highly sensitive transduction for synthetic oligos, DNA and RNA. Graphite pencil electrode is shown useful as a solid support for the biorecognition layer for the DNA hybridization biosensor and at the same time as a signal transducer, but with poor selectivity.; Unlike the conventional DNA hybridization biosensor where both elements are at the same surface, the new concept of separating the biorecognition layer from the transduction layer, by introducing for the first time the use of the commercially available magnetic beads as a solid support of the biorecognition layer, the selectivity of the DNA hybridization biosensor increased dramatically.; We introduced innovative electrochemical routes based on the intrinsic electroactivity of DNA (label-free detection), the use of the metal nanoparticles and enzymes (label detection). The new colloidal gold nanoparticle-based electrochemical DNA hybridization detection at disposable screen-printed electrodes has been combined with an advanced biomagnetic processing technology that couples an efficient magnetic removal of non-hybridized DNA with low-volume magnetic mixing. A new electrochemical multi-enzyme coding technology aimed at extending electrical DNA assays to the simultaneous analysis of multiple targets has been introduced.; Various amplification strategies have been used to enhance the sensitivity of these novel DNA hybridization electrical biosensors. A dramatically enhanced accumulation of purine nucleobases in the presence of copper ions has been used for amplifying the adsorptive stripping hybridization signals. A new method of DNA hybridization detection based on polymeric carrier spheres carrying a large number of gold nanoparticles has been introduced as a novel amplification strategy.; The optimization, characterization and attractive performance of all these novel DNA hybridization electrical biosensors will lead to a significant improvement on the DNA hybridization biosensors in the future.