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 (IC 50 = 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. Chemotherapy is an essential systemic component in modern multimodal cancer treatment, yet one of the main disadvantages of anticancer chemotherapeutics is toxicity to the normal tissue. The use of nano-sized carriers as intracellular transporters for the active substances not only promises to reduce the total drug amount administered, while potentially improving the treatment's efficiency by enhancing the local dose in the tumour, but also can help to improve the specificity and targeting of the active substance, thereby reducing the side-effects associated with chemotherapy 1. In nano-carriers, drugs can be transported to the tumour site through the enhanced permeability and retention effect 2-4 , magnetic targeting 5-8 and protected until they find a triggering stimuli to release, like pH variations 9-12 , temperature 13,14 , radiation-induced release 15-19. The use of iron oxide nanoparticles in the construction of nano-systems for the delivery of chemotherapeutics not only enables active magnetic targeting to the tumour site, but also offers additional functions that make them suitable for diagnosis (contrast substance in MRI 20-22) or enhanced anticancer activity using hyperthermia 23. Conjugation with other compounds can add to the multi-functionality of these nanomaterials and implement properties such as increased and/or specific 24-26 internalization in cancer cells, but can also help to modulate the

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An explanation is presented for the formation of periodic structures on solid surfaces under powerful laser irradiation through an analogy to the Bénard effect.

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