Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and ...magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.
The rational design of complex nanostructures is of paramount importance to gain control over their chemical and physical properties. Recently, magnetic-plasmonic heterostructured nanocrystals have ...been recognized as key players in nanomedicine as multifunctional therapeutic-diagnostic tools and in catalysis. Here we show how the properties of gold-iron oxide heterostructured nanocrystals can be tuned by chemical doping of the magnetic subunit. The divalent cations in the iron oxide were substituted with cobalt and manganese to obtain a general formula Au-MFe
2
O
4
(M = Fe, Co, Mn). Magnetic properties of the heterostructures could be tuned, while maintaining well-defined plasmon resonance signatures, confirming the dual magnetic-plasmonic functional capability of these nanostructures.
Direct interactions between nanoparticles of Mn‐doped magnetite or maghemite (clearly differentiated by Raman spectroscopy) grouped in spherical clusters minimize the effect related to their ...characteristic magnetic dead layer at the surface. Hence, the clustering process jointly with the manganese doping renders these ferrite nanostructures very attractive as displaying increased saturation magnetization, offering, consequently, outstanding values of the specific absorption rate (SAR) for heat delivery. The whole picture for bio‐related applications has been considered, with issues related to magnetic manipulation, colloidal stability, and biocompatibility.
Spinel manganese: Mn‐doped magnetite or maghemite nanoparticles (see figure) (clearly differentiated by Raman spectroscopy), grouped in spherical clusters, offer synergy effects when considering the complete picture of bio‐related applications, with issues related to magnetic manipulation, colloidal stability, biocompatibility, and, particularly, heat delivery.
Magnetite nanoparticles (NPs) are extensively investigated for biomedical applications, particularly as contrast agents for Magnetic Resonance Imaging and as heat mediators in Magnetic Fluid ...Hyperthermia. For the latter, one of the goal of the research is to obtain materials with improved hyperthermic properties. A valuable strategy is the increase of the magnetic anisotropy of commonly employed magnetite through the total or partial substitution of Fe2+ ions with Co2+ ions. Here we present a study on a family of 8nm Co-doped magnetite NPs (CoxFe3−xO4), with composition ranging from pure magnetite (x=0) to stoichiometric cobalt ferrite (x=1), aimed to investigate the evolution of the hyperthermic properties with the increase of Co content. We found that the addition of a small amount of Co is enough to sharply increase the Specific Absorption Rate (SAR). The SAR further increases with x but it reaches a maximum for an intermediate value (x=0.6). Such anomalous behavior is ascribed to the intrinsic magnetic properties of the material, and, in particular, to the magnetic anisotropy, which displays the same peculiar trend. The Co-doping thus may represent an effective strategy to improve the poor hyperthermic efficiency of very small magnetite NPs (<10nm).
•A series of 8nm non-stoichiometric cobalt ferrite nanoparticles was synthesized.•The Co:Fe molar ratio was varied systematically from 0 to 0.5.•The SAR was observed to have a maximum at intermediate Co content.•The hyperthermic results are explained on the basis of the magnetic anisotropy.•Co-doping is an effective strategy to improve the SAR of Fe3O4 NPs less than 10nm.
Display omitted
•Synthesis of out-of equilibrium Au3LixM1-x (M = Fe, Ni, Co) nanoalloys through colloidal chemistry routes.•Lithium incorporation helps stabilize the L12 intermetallic ...nanoalloy.•Co-reduction of Au and M precursors with Butyllithium gives random alloys.•Pre-formed Au seeds act as template for the formation of the intermetallic nanoalloy containing Li and M.•Plasmonic resonance is blue shifted and broadened with respect to Au NPs.
Nanoalloys combining magnetic and plasmonic properties are interesting systems for catalysis and photo-catalysis, magneto-optics, nanomagnetism and fundamental studies. Nevertheless, their synthesis is challenging due to the immiscibility of Au and 3d magnetic metals at mild temperatures in equilibrium conditions. In this work we prepared through colloidal chemistry synthesis Au3LixM1-x (M = Fe, Ni or Co) nanoalloys and studied the synthetic conditions that affect the transition between a disordered and an ordered L12 intermetallic alloy crystal phase. We found that Au seeds act as templates for the formation of the intermetallic nanoalloys, and that lithium (coming from the Butyllithium reducing agent injected after the seeds formation) plays a fundamental role in the stabilization of the intermetallic phase. By tuning the synthetic parameters, we were able to tune the Fe content in Au3LixFe1-x intermetallic nanoalloys from 0.6 to 2.6 %, also tuning the magnetic moment of the nanoalloys. All the synthesized nanoalloys were able to sustain a plasmonic resonance in the visible range, which is blue shifted and broadened with respect to Au NPs. Our results can open colloidal synthesis to novel crystal phases and nanomaterials combining plasmonic and magnetic functionalities at the nanoscale.
PDF
