Shaping Magnetic Fields to Direct Therapy to Ears and Eyes

Abstract

Magnetic fields have the potential to noninvasively direct and focus therapy to disease targets. External magnets can apply forces on drug-coated magnetic nanoparticles, or on living cells that contain particles, and can be used to manipulate them in vivo. Significant progress has been made in developing and testing safe and therapeutic magnetic constructs that can be manipulated by magnetic fields. However, we do not yet have the magnet systems that can then direct those constructs to the right places, in vivo, over human patient distances. We do not yet know where to put the external magnets, how to shape them, or when to turn them on and off to direct particles or magnetized cells-in blood, through tissue, and across barriers-to disease locations. In this article, we consider ear and eye disease targets. Ear and eye targets are too deep and complex to be targeted by a single external magnet, but they are shallow enough that a combination of magnets may be able to direct therapy to them. We focus on how magnetic fields should be shaped (in space and time) to direct magnetic constructs to ear and eye targets.

Polymer–iron oxide composite nanoparticles for EPR-independent drug delivery

“…For clinical translation of magnetophoretic delivery and evaluation, one needs to design magnetic arrays that can generate sufficiently strong field gradients within tissues of interest, as well as subsurface imaging modalities with millimeter resolution. Recent progress in the design of Halbach arrays indicate the possibility of producing sizable field gradients in tissue at depths of 10 cm, at much greater strengths than that produced by dipolar magnets of comparable size [36, 37]. With regard to locating tumors, high-resolution imaging of vascularized tissues is already addressable by MR as well as by ultrasound [38], photoacoustic tomography [39], and optical coherence tomography [40].…”

Advances in nano-based inner ear delivery systems for the treatment of sensorineural hearing loss

“…For example, superparamagnetic iron oxide nanoparticles (SPIONs), gold nanoparticles, and cationic polymer carriers may be used for bioimaging by MRI, confocal laser microscopy, two-photon luminescence, etc… [39,42–46] The inherent magnetic properties of SPIONs also allows for greater control of drug delivery and dispersion within the inner ear by application of an external magnet [42,43,47–49]. Nanoparticles such as cationic polymers and cationic liposomes offer non-viral vector options for gene therapy delivery, which reduces the immunogenicity, inflammatory responses, and risk of insertional mutagenesis [50–56].…”

Quantifying the motion of magnetic particles in excised tissue: Effect of particle properties and applied magnetic field

“…Substantial evidence indicates that particle characteristics (size, surface chemistry, volume of magnetic content) influence their motion through biological media such as mucus 18 , liquids and gels 19 , and brain tissue 10,11 . In mucus 18 , modifying particle size and coating led to 10 fold and 10,000 fold changes in diffusion respectively.…”