Biosensing of DNA through difference in interaction between microparticle and glass plate based on particle...

A novel approach for detecting DNA without labeling the target DNA was developed based on the particle dissociation behavior in a combined acoustic-gravitational field. The particles, which are tethered on a glass plate via intermolecular interactions (F_bind), are dissociated by the resultant force of the acoustic radiation force (F_ac), which is a function of the applied voltage (V), and the sedimentation force. In this system, V required for particle dissociation is dependent on F_bind. The differences in F_bind were exploited for detecting the target DNA. A glass plate and polystyrene (PS) particles were respectively modified with anchor and capture DNAs. The target DNA induces immobilization of the PS particles on the glass plate through sandwich hybridization, with a large accompanying F_bind. In the absence of the target DNA, the anchor DNA on the glass plate interacted weakly with the capture DNA on the PS particles via direct binding (small F_bind). The particle dissociation behavior varies based on the concentration of the target DNA due to changes in the ratio of the PS particles tethered through direct binding and sandwich hybridization. Target DNA with a length exceeding 12 base pairs (bps) can be detected on the picomolar scale at concentrations of 10^-12 to 10^-5 M. This detection scheme was applied to a specific sequence of HIV-2 with 20 bps, achieving a picomolar detection limit.