3D-modeling the interaction of magnetic hydroxyapatite and iron oxide/Polyhydroxyalkanoates nanoparticles with breast tumoral cells (MCF-7) to optimize hyperthermia therapy: A Cryo-SXT and CryoXANES approach

Cancer still represents the major cause of death worldwide due to its multifactorial origin like the altered metabolism. In this scenario, the inhibition of  mitochondrial function by calcium phosphates (CaP) nanoparticles (NPs) have attracted attention as they allow a persistent influx of calcium. Albeit their advantages, these nanoplatforms can induce a lower cytotoxic effect on normal cells. To circumvent this problem, we have recently modified the CaP NPs by providing them with an iron oxide core and polyethylenimine layer that endows the nanosystem with superparamagnetic properties (hereafter N@P@H NPs). This magnetic effect is important to provide a triple antitumoral approach by loading the NPs with antitumoral drugs that will exert a synergic effect with the released constituent calcium ions while simultaneously inducing hyperthermia. To demonstrate the importance of Ca2+ in the antitumoral effec, the N@P@H NPs activity has been compared to the one exhibited by NPs with the same iron oxide core and a novel polyhydroxy butyrate shell (N@P@PBPHH NPs). Preliminary TEM analysis showed that the cell death is associated to mitochondrila disfunction. However, TEM only allows a constrained resolution that hinders the quantitative analysis of the mitochondrial structural changes. In a similar manner, when cutting the samples for TEM observation, the hardness of the N@P@H NPs can be responsible for the nanomaterial removable. Finally, the high attachment of the N@P@H NPs to the cell membrane leads to the possibility of overestimating the quantification of intracellular calcium. Therefore, further NPs:cell interactions must be modelled with a non-invasive  method that can offer high-contrast and native ultra-structure. This information is crucial to localize the intracellular accumulation of the NPs. For these reasons,  we propose to use of Cryo-SXT to collect comprehensive three-dimensional data. Simultaneosly, we aim to determine the chemical fingerprint of the calcium deposition by employing  CryoXANES.