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This work describes a method of investigating the hybridization kinetics of target oligonucleotides with peptide nucleic acid (PNA) probes immobilized on the surface of microfluidic channel through monitoring the changes of streaming potentials.Streaming potentials are generated when a pressure-driven flow passes over a charged surface and are useful in characterizing the surface zeta-potential and charge density.Previously Alvarez and coworkers reported using streaming potential principle to achieve real-time protein detection and study protein-protein interaction1,2.Compared with other surface-based techniques,the streaming potential method has the advantages in its simplicity,low lost,and no need of labeling.In this work,we present the detection of DNA by streaming potentials based on the change of charge density of PNA coating layers by the formation of PNA/DNA complexes.The hybridization of DNA with PNA brings in more negative charges through the phosphate groups on DNA backbones,which causes decrease of streaming potential signals (Figure 1).In a hybridization experiment,PNA is immobilized on a glass slide,which is assembled with PDMS into a microfluidic channel where streaming potential measurement is carried out.A syringe pump is applied to control the liquid motion to generate stable streaming potentials.The time response of streaming potentials in a hybridization event showed an exponential increase of signal versus time,similar to the results obtained in parallel experiments using fluorescence scanning to monitor hybridization (Figure 2).The method has a detection limit of 10 nM DNA,due to the background noise caused by non-specific binding.The change of streaming potentials becomes saturated when DNA concentration is above 200 nM,which defines the upper limit of the method for a quantitative DNA detection.The preliminary results have demonstrated the streaming potential measurement to be a simple and label-free method for DNA detection and kinetic study.Further explorations are undergoing to broaden the DNA detection range and enhance the detection specificity.