Sequence-specific label-free DNA sensors based on silicon nanowires

Highly sensitive and sequence-specific DNA sensors were fabricated based on silicon nanowires (SiNWs) with single stranded (ss) probe DNA molecules covalently immobilized on the nanowire surfaces, Label-free complementary (target) ss-DNA in sample solutions were recognized when the target DNA was hybridized with the probe DNA attached on the SiNW surfaces, producing a change of the conductance of the SiNWs. For a 12-mer oligonucletide probe, 25 pM of target DNA in solution was detected easily (signal/noise ratio > 6), whereas 12-mers with one base mismatch did not produce a signal above the background noise.