Optimization of iron oxide nanoparticles for MRI-guided magnetic hyperthermia tumor therapy: reassessing the role of shape in their magnetocaloric effect.

Superparamagnetic iron oxide nanoparticles have hogged the limelight in different fields of nanotechnology. Surprisingly, notwithstanding the prominent role played as agents in magnetic hyperthermia treatments, the effects of nanoparticle size and shape on the magnetic hyperthermia performance have not been entirely elucidated yet. Here, spherical or cubical magnetic nanoparticles synthesized by a thermal decomposition method with the same magnetic and hyperthermia properties are evaluated. Interestingly, spherical nanoparticles displayed significantly higher magnetic relaxivity than cubic nanoparticles; however, comparable differences were not observed in specific absorption rate (SAR), pointing out the need for additional research to better understand the connection between these two parameters. Additionally, the as-synthetized spherical nanoparticles showed negligible cytotoxicity and, therefore, were tested in vivo in tumor-bearing mice. Following intratumoral administration of these spherical nanoparticles and a single exposure to alternating magnetic fields (AMF) closely mimicking clinical conditions, a significant delay in tumor growth was observed. Although further in vivo experiments are warranted to optimize the magnetic hyperthermia conditions, our findings support the great potential of these nanoparticles as magnetic hyperthermia mediators for tumor therapy.

Correction: Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization.

Correction for 'Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization' by Esther Pozo-Torres et al., Soft Matter, 2020, 16, 3257-3266, DOI: 10.1039/C9SM02512J.

Fe3O4-Au Core-Shell Nanoparticles as a Multimodal Platform for In Vivo Imaging and Focused Photothermal Therapy.

In this study, we report the synthesis of gold-coated iron oxide nanoparticles capped with polyvinylpyrrolidone (Fe@Au NPs). The as-synthesized nanoparticles (NPs) exhibited good stability in aqueous media and excellent features as contrast agents (CA) for both magnetic resonance imaging (MRI) and X-ray computed tomography (CT). Additionally, due to the presence of the local surface plasmon resonances of gold, the NPs showed exploitable "light-to-heat" conversion ability in the near-infrared (NIR) region, a key attribute for effective photothermal therapies (PTT). In vitro experiments revealed biocompatibility as well as excellent efficiency in killing glioblastoma cells via PTT. The in vivo nontoxicity of the NPs was demonstrated using zebrafish embryos as an intermediate step between cells and rodent models. To warrant that an effective therapeutic dose was achieved inside the tumor, both intratumoral and intravenous routes were screened in rodent models by MRI and CT. The pharmacokinetics and biodistribution confirmed the multimodal imaging CA capabilities of the Fe@AuNPs and revealed constraints of the intravenous route for tumor targeting, dictating intratumoral administration for therapeutic applications. Finally, Fe@Au NPs were successfully used for an in vivo proof of concept of imaging-guided focused PTT against glioblastoma multiforme in a mouse model.

Clickable iron oxide NPs based on catechol derived ligands: synthesis and characterization.

Clickable magnetic nanoparticles have attracted great attention as potential nanoplatforms for biomedical applications because of the high functionalization efficiency of their surfaces with biomolecules, which facilitates their bio-compatibilization. However, the design and synthesis of clickable NPs is still challenging because of the complexity of the chemistry on the magnetic NP surface, thus robust methods that improve the ligand synthesis and the transfer of magnetic NPs in physiological media being in high-demand. In this work, we developed a versatile and enhanced synthetic route to fabricate potentially clickable IONPs of interest in nanomedicine. Catechol anchor ligands with different stereo-electronic features were synthetized from a hetero bi-functional PEG spacer backbone. The resulting catechol ligands transferred in good yields and high stability to magnetic NPs by an improved energetic ligand exchange method that combines sonication and high temperature. The azido functionalized IONPs exhibited excellent characteristics as T2 MRI contrast agents with low cytotoxicity, making these clickable magnetic NPs promising precursors for nanomedicines.