Efficient uptake and retention of iron oxide-based nanoparticles in HeLa cells leads to an effective intracellular delivery of doxorubicin

The purpose of this study was to construct and characterize iron oxide nanoparticles (IONP_CO) for intracellular delivery of the anthracycline doxorubicin (DOX; IONP_DOX) in order to induce tumor cell inactivation. More than 80% of the loaded drug was released from IONP_DOX within 24 h (100% at 70 h). Efficient internalization of IONP_DOX and IONP_CO in HeLa cells occurred through pino- and endocytosis, with both IONP accumulating in a perinuclear pattern. IONP_CO were biocompatible with maximum 27.9% ± 6.1% reduction in proliferation 96 h after treatment with up to 200 µg/mL IONP_CO. Treatment with IONP_DOX resulted in a concentration- and time-dependent decrease in cell proliferation (IC₅₀ = 27.5 ± 12.0 μg/mL after 96 h) and a reduced clonogenic survival (surviving fraction, SF = 0.56 ± 0.14; versus IONP_CO (SF = 1.07 ± 0.38)). Both IONP constructs were efficiently internalized and retained in the cells, and IONP_DOX efficiently delivered DOX resulting in increased cell death vs IONP_CO.