Biomagnetic neurosensors.

In this report we demonstrate the first analytical application of biomagnetic field detection at nerve fibers for biosensing purposes. A ferrite core toroid surrounding the nerve, coupled to a low-noise, low-input-impedance amplifier, is used to inductively detect the compound action current (CAC) in crayfish giant axons upon stimulation of nerve firing. Detection of the local anesthetic lidocaine, which blocks neuronal conduction by binding in the ion channel of the voltage-gated sodium channel receptor, is achieved by monitoring the disappearance of the CAC. The application of this novel detection principle to the screening of neurotoxic and neuromodulatory drugs and natural product extracts is proposed.