Electrochemical Discrimination between G‑Quadruplex and Duplex DNA

Analytical tools enabling the discrimination between duplex DNA and G-quadruplex DNA are necessary to unravel the biological function(s) of G-quadruplexes. A methodology relying on the electrochemical response of the electroactive hexaammineruthenium­(III) cation at DNA-modified surfaces is presented. A characteristic voltammetric peak is evidenced for all the investigated G-quadruplex sequences, encompassing various types of folding and numbers of quartets. In contrast, no such peak is detected for dsDNA sequences. The occurrence of the voltammetric peak is the consequence of a strong association between the hexaammineruthenium ligand and the surface-immobilized G-quadruplexes. The peak potential points to a significant contribution of nonelectrostatic interactions between the electroactive ligand and G-quadruplexes. The very good efficiency of the discrimination methodology is demonstrated by comparing a G-quadruplex and its corresponding duplex

Imaging Redox Activity at Bipolar Electrodes by Indirect Fluorescence Modulation

Bipolar electrochemistry (BPE) is nowadays well-known but relatively underexploited and still considered as unconventional. It has been used, among others, in the frame of materials science and most importantly has also found very promising applications in analytical chemistry. Here, we extend this emerging field of analytical applications to the development of a new sensing concept based on indirect BPE. This approach is based on the generation of local pH gradients which will allow detecting indirectly redox-active molecules due to a modulation of the fluorescence intensity in the vicinity of a bipolar electrode

Rapid and Selective Detection of Proteins by Dual Trapping Using Gold Nanoparticles Functionalized with Peptide Aptamers

A colorimetric platform for the fast, simple, and selective detection of proteins of medical interest is presented. Detection is based on the aggregation of two batches of peptide functionalized gold nanoparticles via the dual-trapping of the protein of interest. As proof of concept, we applied our platform to the detection of the oncoprotein Mdm2. The peptide aptamers used for the functionalization are based on the reported binding sequences of proteins p53 and p14 for the oncoprotein. Rapid aggregation, and a color change from red to purple, was observed upon addition of Mdm2 with concentrations as low as 20 nM. The selectivity of the system was demonstrated by the lack of response upon addition of bovine serum albumin (in large excess) or of a truncated version of Mdm2, which lacks one of the peptide binding sites. A linear response was observed between 30 and 50 nM of Mdm2. The platform reported here is flexible and can be adapted for the detection of other proteins when two binding peptide aptamers can be identified. Unlike current immunoassay methods, it is a one-step and rapid method with an easy readout signal and low production costs