Electrochemical Characteristics of a DNA Modified Electrode as a Function of Percent Binding
Year: 2019
Type: article
Abstract: Electrochemical characteristics of immobilized double-stranded DNA (dsDNA) on a Au electrode were studied as a function of coverage using a home-built optoelectrochemical method. The method allows probing of local redox processes on a 6 μm spot by measuring both differential reflectivity (SEED-R) and interferometry (SEED-I). The former is sensitive to redox ions that tend to adsorb to the electrode, while SEED-I is sensitive to nonadsorbing ions. The redox reaction maxima, R max and Δ max from SEED-R and SEED-I, respectively, are linearly proportional to amperometric peak current, I max . The DNA binding is measured by a redox active dye, methylene blue, that intercalates in dsDNA, leading to an R max . Concomitantly, the absence of Δ max for [Fe(CN) 6 ] 4–/3– by SEED-I ensures that there is no leakage current from voids/defects in the alkanethiol passivation layer at the same spot of measurement. The binding was regulated electrochemically to obtain the binding fraction, f, ranging about three orders of magnitude. A remarkably sharp transition, f = f T = 1.25 × 10 –3, was observed. Below f T, dsDNA molecules behaved as individual single-molecule nanoelectrodes. Above the crossover transition, R max, per dsDNA molecule dropped rapidly as f –1/2 toward a planar-like monolayer. The SEED-R peak at f ∼ 3.3 × 10 –4 (∼270 dsDNA molecules) was (statistically) robust, corresponding to a responsivity of ∼0.45 zeptomoles of dsDNA/spot. Differential pulse voltammetry in the single-molecule regime estimated that the current per dsDNA molecule was ∼4.1 fA. Compared with published amperometric results, the reported semilogarithmic dependence on target concentration is in the f > f T regime.
Source: Analytical Chemistry
Authors: Rahul Tevatia, Abhijeet Prasad, Ravi F. Saraf
Institution: University of Nebraska–Lincoln
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
Funder: National Cancer Institute
Awards: G1454457989, G3612573575, A Prognostic Blood Test to Monitor Pancreatic Cancer Treatment by MiRNA Profiling, Profiling Circulating miRNA Without PCR for Early Detection of Pancreatic Cancer, G7674455900, High Specificity MicroRNA Microarray Analysis without PCR for Cancer Screening and Research
OpenAlex ID: W2958169348