Ultra-sensitive dielectrophoretic surface charge multiplex detection inside a micro-dielectrophoretic device.

Label-free dielectrophoretic force-based surface charge detection has shown great potential for highly sensitive and selective sensing of metal ions and small biomolecules. However, this method suffers from a complex calibration process and measurement signal interference in simultaneous multi-analyte detection, thus creating difficulties in multiplex detection. We have developed a method to overcome these issues based on the optical discrimination of the dielectrophoretic behaviors of multiple microparticle probes considering the surface charge difference before and after self-assembling conjugation. In this report, we demonstrate and characterize this dielectrophoretic force-based surface charge detection method with particle probes functionalized by various biomolecules. This technique achieved an attomolar limit of detection (LOD) for Hg2+ in distilled water and a femtomolar LOD in drinking water using DNA aptamer-functionalized particle probes. More importantly, using two different DNA aptamer-functionalized particle probes for Hg2+ and Ag+, label-free dielectrophoretic multiplex detection of these species in drinking water with a femtomolar and a nanomolar LOD was achieved for the first time.