Table 2.

Application of an external magnetic field in drug-delivery systems with different mechanisms.

mechanism	frequency	drug-delivery system (magnetic particle)	key observations
heating [139]	220–260 kHz	poly(N-isopropylacrylamide)-based nanogels	on-demand drug release through on–off mechanism
heating [140]	200 kHz	hydrogels composed of magnetic particles	pulsatile release properties over multiple cycles and multiple days
mechanical deformation [30]	10 kHz	liposomes attached to chains of magnetic particles	defects on the liposomal walls trigger the release of encapsulated drugs
mechanical deformation [141]	0 Hz (static)	core–shell particle with grafted PAA-b-PPEGMA and encapsulated enzymes and therapeutic chemicals	shielded polymer brush barrier is overcome under a weak magnetic field, leading to the merge of enzyme and substrate, namely ‘magnetic field remotely controlled selective biocatalysis’
magnetic guidance [31]	0 Hz	poly(lactic-co-glycolic acid)-based nanoparticles loaded with paclitaxel	eight-fold increase in tumour accumulation and about twofold longer survival time
magnetic guidance [133]	0 Hz	iron oxide-coated phosphollipid-polyethylene glycol	disrupting endothelial adherens junctions
magnetic guidance [10]	0 Hz	lactoferrin-tethered magnetic double emulsion nanocapsules	high tumour accumulation and efficient suppressing of cancer growth