Comparison of two innovatives approaches for bacterial detection: paramagnetic nanoparticles and self-assembled multilayer processes

Transfusion medicine is a field that has developed in the second half of the last century. Very rapidly, however, it became clear that this approach also carried its problems, such as the incompatibility of red blood cells and plasma between donors and recipients, and the possibility of transmitting viral and bacterial infections. An immunomagnetic biosensor for the label-free detection of a bacterial model, Escherichia coli, is described and compared to a self assembled multilayer system reported previously. The paramagnetic nanoparticles layer attracted to, and formed on, the gold electrode surface via a magnetic field up to 300 mT is not totally blocking for the redox probe comparing to the thiol self assembled monolayer (a biotin thiol and a spacer thioalcohol). Moreover, the modeling of the Nyquist spectra obtained by electrochemical impedance spectroscopy for increasing concentrations of E. coli shows for both system a sigmoid variation of the polarization resistance with increasing logarithmic concentration of bacteria. A sensitivity slope of 10.675 was obtained for the immunomagnetic sensor compared to 6.832 for the self assembled multilayer process, this indicating the higher sensitivity of the paramagnetic nanoparticles biosensor.