Dynamic Inversion Enables External Magnets To ConcentrateFerromagnetic Rods to a CentralTarget.

Theability to use magnets external to the body to focus therapy to deeptissue targets has remained an elusive goal in magnetic drug targeting.Researchers have hitherto been able to manipulate magnetic nanotherapeuticsin vivo with nearby magnets but have remained unable to focus thesetherapies to targets deep within the body using magnets external tothe body. One of the factors that has made focusing of therapy tocentral targets between magnets challenging is Samuel Earnshaw’stheorem as applied to Maxwell’s equations. These mathematicalformulations imply that external static magnets cannot create a stablepotential energy well between them. We posited that fast magneticpulses could act on ferromagnetic rods before they could realign withthe magnetic field. Mathematically, this is equivalent to reversingthe sign of the potential energy term in Earnshaw’s theorem,thus enabling a quasi-static stable trap between magnets. With invitro experiments, we demonstrated that quick, shaped magnetic pulsescan be successfully used to create inward pointing magnetic forcesthat, on average, enable external magnets to concentrate ferromagneticrods to a central location. [ABSTRACT FROM AUTHOR]