Evidence of modular responsiveness of osteoblast-like cells exposed to hydroxyapatite-containing magnetic nanostructures

Simple Summary Current research on nanocomposite materials with tailored physical–chemical properties is increasingly advancing in biomedical applications for bone regeneration. In this study, occurrence of differential responsiveness to dextran-grafted iron oxide (DM) nanoparticles and to their hybrid nano-hydroxyapatite (DM/n-HA) counterpart was investigated in human-derived, osteoblast-like cells. Sensitivity of cells in the presence of DMs or DM/n-HAs was evaluated in terms of cytoskeletal dynamics. Remarkably, it was shown that effects triggered by the DM are no more retained when DM is embedded onto DM/n-HA nanocomposites. In parallel, analyses on the expression of genes involved in (a) intracellular signaling pathways triggered by ligands or cell interactions with elements of the extracellular matrix, (b) modulation of processes such as cell cycle arrest, apoptosis, senescence, DNA repair, metabolism changes, and (c) iron homeostasis and absorption through cell membranes, indicated that the DM/n-HA-treated cells retain tracts of physiological responsiveness unlike DM-treated cells. Overall, a shielding effect by the n-HA was assumed (masking the DM’s cytotoxicity), and a modular biomimicry of the DM/n-HA nanocomposites. On these bases, the biocompatibility of n-HA associated to DM’s magnetic responsiveness offer a combination of structural/functional features of these nano-tools for bone tissue engineering, for finely acting within physiological ranges. Abstract The development of nanocomposites with tailored physical–chemical properties, such as nanoparticles containing magnetic iron oxides for manipulating cellular events at distance, implies exciting prospects in biomedical applications for bone tissue regeneration. In this context, this study aims to emphasize the occurrence of differential responsiveness in osteoblast-like cells to different nanocomposites with diverse features: dextran-grafted iron oxide (DM) nanoparticles and their hybrid nano-hydroxyapatite (DM/n-HA) counterpart. Here, responsiveness of cells in the presence of DMs or DM/n-HAs was evaluated in terms of cytoskeletal features. We observed that effects triggered by the DM are no more retained when DM is embedded onto the DM/n-HA nanocomposites. Also, analysis of mRNA level variations of the focal adhesion kinase (FAK), P53 and SLC11A2/DMT1 human genes showed that the DM/n-HA-treated cells retain tracts of physiological responsiveness compared to the DM-treated cells. Overall, a shielding effect by the n-HA component can be assumed, masking the DM’s cytotoxic potential, also hinting a modular biomimicry of the nanocomposites respect to the physiological responses of osteoblast-like cells. In this view, the biocompatibility of n-HA together with the magnetic responsiveness of DMs represent an optimized combination of structural with functional features of the DM/n-HA nano-tools for bone tissue engineering, for finely acting within physiological ranges.