Real-time measurements of PNA:DNA hybridization kinetics with silicon nanowire biosensors

Real-time electronic detection of peptide nucleic acid (PNA):DNA hybridization is demonstrated with silicon nanowire (Si-NW) biosensors. A stable baseline platform is crucial for obtaining the Si-NW response for biosensing applications. An integrated Si-NW auto-sampler is demonstrated and used for kinetic molecular binding measurements. The equilibrium association constant is determined to be K_A≈7×10⁶ M^-1 in 1 mM ionic strength buffer. The surface density of hybridized DNA is determined to be ~10¹² molecules/cm² with a radiolabeled DNA-P³² assay. A 30× reduction in the measurement drift in Si-NW sensor response is obtained from 1.6 nA/hr to 0.04 nA/hr by using a differential measurement.