The role of polarization-induced reorientation of DNA strands on organic field-effect transistor-based biosensors sensitivity at high ionic strength

The detection of the intrinsic charge of biochemical molecules is a promising strategy for the fabrication of field-effect transistor (FET)-based sensors for direct, non-destructive detection of several biochemical reactions. Nevertheless, the high ionic concentration of standard environments for biochemical species represents a significant limitation to this sensing strategy. Here, an investigation on the physical mechanisms behind the ability of an organic FET-based sensor to detect DNA hybridization at high ionic strengths is proposed. The capability of the device to correctly detect single-stranded DNA oligonucleotides and their hybridization with a complementary target sequence has been analyzed in detail. In particular, the electrical response in solutions with different ionic strengths was investigated and put in relation with the nano-scale properties of DNA strands employed as receptors. Fluorescence analysis shows that it is possible to electrically modify their orientation and consequently improve the device sensitivity in conditions close to those occurring during in vivo hybridization.