An ultra sensitive DNA detection by using gold nanoparticle multilayer in nano-gap electrodes

Chapter 26 Thick- and thin-film DNA sensors

“…Very sensitive methods are always required for DNA sensing. Although enough sensitivity to avoid PCR amplification has been achieved by use of enzymatic labels [12,14,26,28] or metal tags [42], most of the assays routinely start with a PCR or other biochemical amplification. Moreover, although label-free formats are used, most of the strategies followed to obtain the analytical signal involve several washing steps and need the use of labelled reagents (or labelling procedures) or indicators, which complicates the assay performance.…”

“…These arrays are constructed on silicon substrate and the gaps between electrodes are functionalised using glycidosypropyltrimethoxysilane [41] or 7-octenyltrimethoxysilane [5] and then amino modified ssDNA probes are covalently attached. Other authors modified the gap between electrodes using 3-mercaptopropyltrimethoxysilane [42]. One end of this chemical compound is used to silanise the substrate surface while the thiol end is used to bind gold nanoparticles that are bound to thiolate ssDNA capture probes.…”

“…With respect to colloidal gold, the nanoparticles are usually bound to thiol-terminated DNA molecules [33,41,42], although in other cases [5] the nanoparticles are linked indirectly through biotin-anti-biotin bridges. The detection of gold nanoparticles can be carried out by measuring the changes in the electrical resistance or capacitance between electrodes usually after a silver enhancement procedure or by anodic stripping voltammetry of the gold (III) obtained after a treatment with an oxidant Br 2 /HBr mixture.…”

“…-Thermal denaturation. It is the most commonly used strategy [6,12,13,15,[20][21][22]29,[34][35][36]42]. It consists of denaturing the dsDNA thermally by using a boiling water bath for sometime and then immersing the tube containing the denaturalised DNA in an icewater bath for a short time in order to retard the re-annealing of the strands.…”

Determination ofSalmonella typhimuriumby a Fluorescence Resonance Energy Transfer Biosensor Using Upconversion Nanoparticles as Labels

“…Gold nanoparticles ($40 nm in diameter) were prepared by the reduction of AuCl À 4 with trisodium citrate according to literature procedures (Tsai, Chang, and Chen 2005;Dubertret, Calame, and Libchaber 2001). Typically, 95.8 mL aqueous solution with 4.2 mL HAuCl 4 (1%) was boiled for 10 min, and 10 mL trisodium citrate (1%) was rapidly added with boiling for 10 min and subsequently another 15 min of stirring without heating.…”