Inductive microcoils for the fast and simple detection of bacterial presence

Inductor microcoils have been proposed as novel analytical tools for the development of microbial magneto-assays using magnetic particles. In this work, microfabricated microcoils are alternatively exploited for the direct determination of bacteria presence in a completely reagentless format. Detection is based in the fact that the conductivity of the bacterial wall contributes to the overall medium conductivity, triggering a change of the magnetic field of the system and the microcoil inductance measured. A fast single measurement of the microcoil inductance allows detection of down to 50 Escherichia coli cells in 0.5 μl of PBS solution. Measurement is also possible directly in water samples, provided that their conductivity is adjusted. Advantages to this approach include fast response times, in a label-free assay format, coupled to the exploitation of devices highly compatible with mass and low cost production.