The influence of the shape of magnetic nanoparticles on magnetic hyperthermia and cellular internalisation

Magnetic nanoparticles are used in magnetic hyperthermia–based cancer treatment. It is unclear how the shape of these nanoparticles influence their cellular uptake and use in this treatment because it is difficult to synthesise nanoparticles with an identical chemical composition while precisely controlling their shape. In this study, we investigated monodisperse magnetite (Fe 3 O 4 ) nanoparticles with an identical composition but different shapes – nanospheres, nanohexagons, and nanocuboids – to evaluate their potential use in magnetic hyperthermia of malignant brain tumours. Magnetic nanoparticles were synthesised via an optimised solvothermal route using aldehydes as shape-directing agents. The heating curves of coated nanoparticles (5 mg/mL) were recorded under different alternating current magnetic field strengths (10, 20, and 30 mT) and a frequency of 98–313 kHz. Nanospheres (12.6 ± 0.14 nm) exhibited the highest specific absorption rate (SAR) calculated using the Box–Lucas method, specifically 1068.7 W/g at 313 kHz and 30 mT; nanohexagons (12.27 ± 0.16 nm) showed moderate heating; and nanocuboids (24 nm) produced a measurable SAR only at 30 mT, reflecting their ferromagnetic nature. Intrinsic loss power (ILP), which is useful to quantify the heating efficiency of magnetic nanoparticles in hyperthermia, revealed a frequency-dependent decrease for nanospheres, consistent with relaxation-dominated heating, whereas ILP remained nearly constant for nanohexagons and nanocuboids due to their greater shape anisotropy. Cellular uptake experiments also demonstrated a strong shape dependence: nanospheres were internalised most efficiently by a glioblastoma cell line, nanohexagons showed intermediate uptake, and nanocuboids showed relatively low uptake, likely due to steric hindrance, aggregation, and inefficient membrane wrapping. Together, these findings demonstrate that the shape of nanoparticles is a critical design parameter because it affects the magnetic state, heating efficiency, and cellular uptake. Nanospheres are particularly promising candidates for translational magnetic hyperthermia applications. • Magnetic nanospheres, nanohexagons, and nanocuboids were synthesised. • Nanospheres exhibited the highest magnetic heating efficiency. • Nanospheres showed the highest internalisation in brain tumour cells.