Current-block nanoelectrode array for label-free detection of proteins and short DNA strands

Conversion of molecular binding events to electrical signals is one of the essential tasks of constructing integrated systems as lab-on-a-chip or high-throughput chemical and bio-molecular analysis tools. We present the construction of an array of current blocking devices capable of translating oligonucleotide hybridization and the biotin-streptavidin interaction into a change in electrical resistance. Each sensor in the array consists of a counter electrode and two 75 nm tall measurement electrodes: control and working electrodes. The attachment of molecular receptors on electrodes is electrochemically programmed. For example, a working electrode is functionalized with a self-assembled monolayer of a particular oligonucleotide while the counter electrode is left intact. By monitoring the differential conductance signal between the two electrodes, specific hybridization of a complementary strand is detected. We demonstrate successful detection of DNA hybridization and small molecule-protein binding. This sensor is cost effective, readily integratable with integrated circuits, easily scalable, and, most importantly, with appropriate ligand immobilization it can be a generic platform for the detection of various biomolecules, cell organelles, viruses and other markers of interest in biology.