A novel impedimetric sensor for detecting LAMP amplicons of pathogenic DNA based on magnetic separation

A novel impedimetric sensor was developed for the detection of loop mediated isothermal amplification (LAMP) amplicons of various foodborne pathogens through combining with a microfluidic system and magnetic separation procedure. The amplified nucleic acid products (amplicons) of the LAMP reaction can adsorb on magnetic beads surface via electrostatic adsorption process. The obtained nucleic acid-magnetic bead composites were re-dispersed in deionized water and the impedance response was measured by injecting the nucleic acidmagnetic bead composites into the microfluidic system. On account of the quite low conductivity (1(similar to)2 mu S cm(-1)) of deionized water, the weak change of charge can be detected by impedance. Thus the abundant negative charges of nucleic acids in the composites can produce an obviously reduction of impedance signal. Based on the principle, the developed impedimetric sensing method was used for sensing various foodborne pathogens including Escherichia coll. O157:H7 (E. coli. O157:H7), Vthrio parahaemolyticus (V. parahaemolyticus), Staphylococcus aureus (S. aureus), and Listeria monocytogenes (L. monocytogenes), which achieved a low detection limit (10 copies). Compared with the conventional gel electrophoresis method, our method is more sensitive and faster, which has a potential for fast and sensitive detection of the LAMP products of various targets.