Stimuli-responsive polymers have potential in drug delivery and tissue engineering applications, as heating can induce separation and shape memory change within a polymer network. Superparamagnetic iron oxide nanoparticles (NPs) can be heated remotely using AC magnetic field stimulation. With a suitable surface coating, NPs can be combined with monomers and polymerised to form nanocomposite hydrogels that can be remotely heated by externally applied AC fields. The aim of this thesis was to progress nanoparticle synthesis, compositing, gel formulation and printing capabilities towards these goals. The first part of the work focused on the synthesis of size controlled NPs, with hydrophilic surface catechol-functional ligands. The nanoparticle surface coverage and effect of the ligands on the particle magnetisation were investigated. The behaviour of magnetic hydrogels in AC fields, specifically their ability to de-swell as a function of the induced temperature change, was investigated. Temperature changes were studied as a function of nanoparticle concentration. Finally, stimulated de-swelling was studied for different formulations; i.e. as a function of the co-monomer and crosslinker content. Using the catechol ligands as excipients for mechanical milling of micron-sized iron-oxide, it was shown that NPs can be generated and their surfaces coated in situ. This process removed the need for a ligand exchange step. The performance of these nano-materials for stimulated de-swelling was also evaluated. NPs prepared by milling were used as additives in 3D printing of nanocomposites. It was shown that the nature of the iron oxide, either bulk or colloidal, affects the penetration of light into the resin formulation and hence the curing depth and spatial resolution that can be achieved. It also has implications for the mechanical behaviour of the printed object. Finally, the effect of build orientation on mechanical properties was studied.