Remote Sensing of Ciliary Beating Using a SQUID Gradiometer

Beating of ependymal cilia in the mammalian brain ventricle causes cerebrospinal fluid circulation. Beating of ependymal cilia is studied in vitro in many laboratories but has not been monitored non-invasively in live animals. We have developed a new method for remote sensing of the magnetic flux density changes associated with the reciprocal movement of a magnetic particle bound to cilia in the lateral ventricle of a newborn rat brain with superconducting quantum interference device (SQUID). We detected an oscillatory signal (10–20 Hz and ca. 10 pT amplitude) from a small neodymium magnetic particle attached to cilia with the SQUID above the specimen; the distance between the cilia to the SQUID sensor was 12 mm. This successful detection provides a new sensing platform that enables the non-invasive measurement of beating of ependymal cilia from a live animal.