DNA-modified surface

These observations were significant to our choice of reactants for probing CT at DNA-modified surfaces. In particular, an upright orientation of the DNA relative to the surface is required to probe DNA-mediated reactions otherwise a more direct reaction between an intercalating probe and the electrode might be possible. Consequently, reactants were selected such that a negative potential could be apphed, thereby initiating reduction of an intercalated redox probe distantly bound within DNA helix. Importantly, the... 

DNA has been used to modify the PSf membrane by blending and immobilizing DNA onto its surface [123,124]. PSf is one of the most important polymeric materials and is widely used in artificial and medical devices. However, when used as a hemodialysis hollow fiber, the blood compatibility of the PSf membrane is not adequate. The hydrophilicity of the DNA-modified surface increased, but the amount of adsorbed protein did not decrease significantly, which indicates that the DNA-modified membrane might have a better blood compatibility. 

Many of these approaches rely on the differential hybridization of target DNAs that are perfectly matched with probe sequences to achieve highly specific and accurate target selection. Other assays use the sensitivity of DNA-mediated charge transport to duplex structure in order to signal the presence of a sequence of interest. Efforts also have been directed toward exploiting non-faradaic processes unique to DNA-modified surfaces as the basis for electrochemical readout. This chapter discusses each of these methods, and is intended to highlight how the DNA/electrode interface can... 

Complementary spectroscopic studies have also helped to elaborate the factors controlling hybridization at DNA-modified surfaces." Surface plasmon resonance has been used to monitor DNA target capture in real time, and has confirmed that the efficiency of hybridization is maximized at surfaces sparsely covered with probe oligonucleotides. ... 

Yu, H. Z., Luo, C. Y., Sankar, C. G., Sen, D. (2003). Voltammetric procedure for examining DNA-modified surfaces quantitation, cationic binding activity, and electron-transfer kinetics. Anal Chem 75, 3902-3907. 

The use of DNA as a template to fabricate mesoscale structures was also demonstrated in a recent work of Torimoto and coworkers. They used preformed, positively charged 3-nm CdS nanoparticles with a thiocholine-modified surface to be assembled into chains by using the electrostatic interaction between positively charged nanoparticle snr-faces and the phosphate groups of DNA. As determined by TEM analysis, the CdS nanoparticles were arranged in a qnasi-one-dimensional dense packing. This revealed interparticle distances of about 3.5 nm, which is almost equal to the height of one helical tnm of the DNA double strand [98]. 

Besides thick-layer DNA/GEC surface, a thin-layer DNA/GEC could be achieved by wet-adsorption of ss- and dsDNA and ODN onto a GEC transducer under static conditions [99,100]. In this case, the hydrated B-DNA form was stabilized over the GEC surface by weaker forces. Unlike the GEC surface modified by the thick DNA layer —produced in dry conditions—the thin-layer DNA/GEC surface required blocking treatment to avoid nonspecific... 

To take advantages of the unique properties of CNTs, a general approach is the immobilization of DNA on CNTs and the further immobilization of the DNA-modified CNTs on an easier-to-handle pure conductor, e.g., GC [26], Ft [121], Au [ 122]. Another approach consists of the prior modification of the pure conductor (GC) with the CNTs through dry-adsorption and the further DNA or DNA derivatives adsorption on the CNT-modified surface [123-125]. 

The phosphate backbone of DNA molecules often results in undesirable electrostatic interactions with the substrate. Although the electrostatic interactions of DNA can be utilized for physical adsorption of DNA to the surface, this process can also lead to the nonspecific physical adsorption of target DNA on the surface. Rather than sample DNA hybridizing to the probe, it can adsorb to the surface and lead to interferences with the final detection call. Nonspecific adsorption effects have primarily been examined by the microarray community. Blocking strategies have been developed to prevent these nonspecific interactions. Succinic anhydride (SA) and bovine serum albumin (BSA) are two common methods to prevent nonspecific adsorption on amine modified surfaces. Blocking strategies are desired to react with or pas-... 

DNA immobilized by organosilane chemistries has proven to be an effective method for measuring impedance changes upon hybridization using both gold and platinum electrodes [21,50]. The effect of different silane chemistries creates differences in the hydrophobicity and hydration levels of the modified surface. The organosilane treatment along with the ssDNA... 

When natural or synthetic DNA molecules interact with electrode surfaces adsorption occurs. The knowledge about the adsorption of nucleic acids onto the electrode surface leads to the development of DNA-modified electrodes, also called electrochemical DNA biosensors [3-6,19-24], An electrochemical DNA biosensor is an integrated receptor-transducer device that uses DNA as the biomolecular recognition element to measure specific binding processes with DNA, using electrochemical transduction. 

The aim of developing DNA-modified electrodes is to study the interaction of DNA immobilized on the electrode surface with analytes in solution and to use the DNA biosensor to evaluate and to predict DNA interactions and damage by health hazardous compounds based on their ability to bind to nucleic acids. In this way, DNA acts as a promoter between the electrode and the biological molecule under study. 

Moreover, by easily controlling the concentration of the DNA solution being dried on GEC platform, a thick or a thin layer of DNA can be formed on the GEC surface by dry adsorption [59]. Depending on the application of the DNA-modified substrate, a thick or thin DNA layer would be necessary. If a stringency control of non-specific DNA adsorption issues is required, a thick DNA layer is more convenient. However, the yield in hybridization is better on a thin DNA layer [59]. 

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