Magnetic field-guided enhancement of nanoparticle uptake and hyperthermia efficacy in 3D tumour models

Magnetic hyperthermia (MH) using iron oxide nanoparticles (MNPs) is a promising cancer treatment strategy, yet its efficacy strongly depends on efficient intracellular nanoparticle delivery. Here, we compared two strategies to enhance MNP uptake by tumour cells: (i) increasing the administered MNP dose and (ii) applying a static magnetic field (MF) gradient to promote nanoparticle-cell interactions and increase availability at the cell surface. Human tumour cell lines, representing distinct challenges for nanoparticle internalisation due to differences in growth behaviour and cellular organisation, were first incubated with glucose-functionalised 11 nm MNPs under two-dimensional (2D) culture conditions to control and quantify intracellular uptake under each strategy. Cells with pre-internalised MNPs were then embedded in collagen-based three-dimensional (3D) tumour models, where MH was applied and therapeutic efficacy was evaluated by confocal microscopy and flow cytometry. While both strategies increased intracellular MNP levels, only MF-assisted internalisation resulted in effective MH-induced cytotoxicity under mild conditions across all tested cell lines. These findings indicate that antitumour MH efficacy is not solely determined by nanoparticle uptake, but also by the strategy used to enhance internalisation, revealing an additional layer of complexity for designing efficient MH protocols.