Characterization and electrochemical response of DNA functionalized 2Â nm gold nanoparticles confined in a nanochannel array

Polyvalent gold nanoparticle oligonucleotide conjugates are subject of intense research. Even though 2 nm diameter AuNPs have been previously modified with DNA, little is known about their structure and electrochemical behavior. In this work, we examine the influence of different surface modification strategies on the interplay between the meso-organization and the molecular recognition properties of a 27-mer DNA strand. This DNA strand is functionalized with different sulfur-containing moieties and immobilized on 2 nm gold nanoparticles confined on a nanoporous alumina, working the whole system as an electrode array. Surface coverages were determined by EXAFS and the performance as recognition elements for impedance-based sensors is evaluated. Our results prove that low DNA coverages on the confined nanoparticles prompt to a more sensitive response, showing the relevance in avoiding the DNA strand overcrowding. The system was able to determine a concentration as low as 100 pM of the complementary strand, thus introducing the foundations for the construction of label-free genosensors at the nanometer scale.