Emergence of magnetic nanoparticles in photothermal and ferroptotic therapies.

With their distinctive physicochemical features, nanoparticles have gained recognition as effective multifunctional tools for biomedical applications, with designs and compositions tailored for specific uses. Notably, magnetic nanoparticles stand out as first-in-class examples of multiple modalities provided by the iron-based composition. They have long been exploited as contrast agents for magnetic resonance imaging (MRI) or as anti-cancer agents generating therapeutic hyperthermia through high-frequency magnetic field application, known as magnetic hyperthermia (MHT). This review focuses on two more recent applications in oncology using iron-based nanomaterials: photothermal therapy (PTT) and ferroptosis. In PTT, the iron oxide core responds to a near-infrared (NIR) excitation and generates heat in its surrounding area, rivaling the efficiency of plasmonic gold-standard nanoparticles. This opens up the possibility of a dual MHT + PTT approach using a single nanomaterial. Moreover, the iron composition of magnetic nanoparticles can be harnessed as a chemotherapeutic asset. Degradation in the intracellular environment triggers the release of iron ions, which can stimulate the production of reactive oxygen species (ROS) and induce cancer cell death through ferroptosis. Consequently, this review emphasizes these emerging physical and chemical approaches for anti-cancer therapy facilitated by magnetic nanoparticles, combining all-in-one functionalities.

Spontaneous Hetero-attachment of Single-Component Colloidal Precursors for the Synthesis of Asymmetric Au-Ag2X (X = S, Se) Heterodimers.

Finding simple, easily controlled, and flexible synthetic routes for the preparation of ternary and hybrid nanostructured semiconductors is always highly desirable, especially to fulfill the requirements for mass production to enable application to many fields such as optoelectronics, thermoelectricity, and catalysis. Moreover, understanding the underlying reaction mechanisms is equally important, offering a starting point for its extrapolation from one system to another. In this work, we developed a new and more straightforward colloidal synthetic way to form hybrid Au-Ag2X (X = S, Se) nanoparticles under mild conditions through the reaction of Au and Ag2X nanostructured precursors in solution. At the solid-solid interface between metallic domains and the binary chalcogenide domains, a small fraction of a ternary AuAg3X2 phase was observed to have grown as a consequence of a solid-state electrochemical reaction, as confirmed by computational studies. Thus, the formation of stable ternary phases drives the selective hetero-attachment of Au and Ag2X nanoparticles in solution, consolidates the interface between their domains, and stabilizes the whole hybrid Au-Ag2X systems.

Monitoring the insertion of Pt into Cu2-xSe nanocrystals: a combined structural and chemical approach for the analysis of new ternary phases.

The tuning of the chemical composition in nanostructures is a key aspect to control for the preparation of new multifunctional and highly performing materials. The modification of Cu2-xSe nanocrystals with Pt could provide a good way to tune both optical and catalytic properties of the structure. Although the heterogeneous nucleation of metallic Pt domains on semiconductor chalcogenides has been frequently reported, the insertion of Pt into chalcogenide materials has not been conceived so far. In this work we have explored the experimental conditions to facilitate and enhance the insertion of Pt into the Cu2-xSe nanocrystalline lattice, forming novel ternary phases that show a high degree of miscibility and compositional variability. Our results show that Pt is mainly found as a pure metal or a CuPt alloy at high Pt loads (Pt : Cu atomic ratio in reaction medium >1). However, two main ternary CuPtSe phases with cubic and monoclinic symmetry can be identified when working at lower Pt : Cu atomic ratios. Their structure and chemical composition have been studied by local STEM-EDS and HRTEM analyses. The samples containing ternary domains have been loaded on graphite-like C3N4 (g-C3N4) semiconductor layers, and the resulting nanocomposite materials have been tested as promising photocatalysts for the production of H2 from aqueous ethanolic solutions.

Facile morphology control of gold(0) structures from aurophilic assemblies.

Different gold microstructures have been synthesized by using supramolecular gold(i) organometallic compounds as templates and Ag nanoparticles as reducing agents. The use of fibers resulting from supramolecular assemblies of neutral gold(i) compounds gives rise to the formation of microrods. The use of supramolecular assemblies from ionic molecules results in spherical or square-based prism gold microstructures, depending on the shape of the supramolecular gold(i) precursor assembly. In addition to temperature and reaction time, solvents exert a strong influence on the formation and morphology of gold structures, as borne out by the example that well-defined star-like morphologies have been obtained in chloroform.

Preparation and Antitumoral Activity of Au-Based Inorganic-Organometallic Nanocomposites.

The synergy between gelator molecules and nanostructured materials is currently a novel matter of study. The possibility to carefully design the skeleton of the molecular entity as well as the nanostructure's morphological and chemical features offers the possibility to prepare a huge variety of nanocomposites with properties potentially different than just the sum of those of the individual building blocks. Here we describe the synthesis and characterization of nanocomposites made by the unconventional combination of phosphine-Au(I)-alkynyl-based organometallic gelating molecules and plasmonic Au nanoparticles. Our results indicate that the interaction between the two moieties leads to a significant degree of aggregation in both hydrophilic and hydrophobic media, either when using DAPTA or PTA-based organometallic molecules, with the formation of a sponge-like hybrid powder upon solvent evaporation. The biological activity of the nanocomposites was assessed, suggesting the existence of a synergetic effect evidenced by the higher cytotoxicity of the hybrid systems with respect to that of any of their isolated counterparts. These results represent a preliminary proof-of-concept for the exploitation of these novel nanocomposites in the biomedical field.

Highly water-stable rare ternary Ag-Au-Se nanocomposites as long blood circulation time X-ray computed tomography contrast agents.

X-ray computed tomography (CT) is a powerful and widely used medical non-invasive technique that often requires intravenous administration of contrast agents (CAs) to better visualize soft tissues. In this work, we have developed a novel CT contrast agent based on ternary Ag-Au-Se chalcogenide nanoparticles (NP). A facile ligand exchange by using a 3 kDa PEGylated ligand with a dithiol dihydrolipoic acid as an anchor group resulted in highly water-soluble and monodisperse nanoparticles. These PEGylated ternary NPs were tested in vivo in mice, showing slow uptake by the mononuclear phagocyte system, long blood circulation times, low toxicity, and very good X-ray contrast, thus being promising candidates as CT contrast agents for clinical applications.

Exploiting Metallophilicity for the Assembly of Inorganic Nanocrystals and Conjugated Organic Molecules.

The accurate engineering of interfaces between inorganic nanocrystals and semiconducting organic molecules is currently viewed as key for further developments in critical fields such as photovoltaics and photocatalysis. In this work, a new and unconventional source of interface interaction based on metal-metal bonds is presented. With this aim, an Au(I) organometallic gelator was exploited for the formation of hydrogel-like nanocomposites containing inorganic nanoparticles and conjugated organic molecules. Noteworthy, the establishment of metallophilic interactions at the interface between the two moieties greatly enhances interparticle coupling in the composites. Thus, we believe that this new hybrid system might represent a promising alternative in several fields, such as in the fabrication of improved light-harvesting devices.

The One Year Fate of Iron Oxide Coated Gold Nanoparticles in Mice.

Safe implementation of nanotechnology and nanomedicine requires an in-depth understanding of the life cycle of nanoparticles in the body. Here, we investigate the long-term fate of gold/iron oxide heterostructures after intravenous injection in mice. We show these heterostructures degrade in vivo and that the magnetic and optical properties change during the degradation process. These particles eventually eliminate from the body. The comparison of two different coating shells for heterostructures, amphiphilic polymer or polyethylene glycol, reveals the long lasting impact of initial surface properties on the nanocrystal degradability and on the kinetics of elimination of magnetic iron and gold from liver and spleen. Modulation of nanoparticles reactivity to the biological environment by the choice of materials and surface functionalization may provide new directions in the design of multifunctional nanomedicines with predictable fate.

Ferro- to antiferromagnetic crossover angle in diphenoxido- and carboxylato-bridged trinuclear Ni(II)2-Mn(II) complexes: experimental observations and theoretical rationalization.

Three new trinuclear heterometallic Ni(II)-Mn(II) complexes have been synthesized using a [NiL] metalloligand, where H2L = N,N'-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)2Mn(OCnn)2(CH3OH)2]·CH3OH (1), [(NiL)2Mn(OPh)2(CH3OH)2][(NiL)2Mn(OPh)2]·H2O (2), and [(NiL)2Mn(OSal)2(CH3OH)2]·2[NiL] (3) (where OCnn = cinnamate, OPh = phenylacetate, OSal = salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal Ni(II) atoms are linked to the central Mn(II) by means of a syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angles of 97.24 and 96.43°, respectively, exhibit ferromagnetic interactions (J(Ni-Mn) = +1.38 and +0.50 cm(-1), respectively), whereas 3 is antiferromagnetic (J(Ni-Mn) = -0.24 cm(-1)), having an Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between the Ni-O-Mn angle and J(Ni-Mn) values, which is in agreement with the experimental results.

Trinuclear heterometallic Cu(II)-Mn(II) complexes of a salen type Schiff base ligand: anion dependent variation of phenoxido bridging angles and magnetic coupling.

Five new trinuclear heterometallic Cu(II)-Mn(II) complexes [(CuL)2Mn(O2CPh)2] (1), [(CuL)2Mn(N3)2] (2), [(CuL)2Mn(NCO)2] (3), [(CuL)2Mn(NO3)2] (4) and [(CuL)2Mn(Sal)2]·CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and Sal = salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between Cu(II) and Mn(II) ions, which results in a final ferrimagnetic ground state with spin 3/2 in the Cu(II)-Mn(II)-Cu(II) trinuclear structure. The weakest antiferromagnetic interaction (J(Cu-Mn) = -7.0 cm(-1)) is observed for 2 having the lowest value of the Cu-O-Mn angle (92.0°), while the strongest antiferromagnetic interaction (J(Cu-Mn) = -26.5 cm(-1)) is observed for 3 having the largest Cu-O-Mn angle (101.4°). Complexes 1, 4 and 5 show average Cu-O-Mn angles of 98.2°, 97.6° and 97.7°, respectively, that lead to intermediate antiferromagnetic interactions (J(Cu-Mn) = -9.6, -9.7, -9.3 cm(-1) respectively).

Photoluminescent CdSe@CdS/2D as potential biocompatible materials.

We have successfully fabricated herein a complex hybrid nanostructure composed of 1D CdSe@CdS nanorods and 2D Mg-Al brucite-like nanosheets. The novel material exhibits enhanced photoluminescence when compared to as-prepared CdSe@CdS rods. The results show that the two different starting materials can be heterogeneously integrated as functional components, the nanorods being aligned in parallel to the hydrotalcite crystals. Of particular interest are the changes in the fluorescence emission lifetime of the nanorods depending on the starting form of the host hydrotalcite (as-such or delaminated). The material enhanced photoluminescence reduces the need for a higher concentration of CdSe@CdS nanorods, a requisite for their biological use as markers.

Layered double hydroxides as carriers for quantum dots@silica nanospheres.

Quantum dot-hydrotalcite layered nanoplatforms were successfully prepared following a one-pot synthesis. The process is very fast and a priori delamination of hydrotalcite is not a prerequisite for the intercalation of quantum dots. The novel materials were extensively characterized by X-ray diffraction, thermogravimetry, infrared spectroscopy, transmission electron microscopy, true color fluorescence microscopy, photoluminescence, and nitrogen adsorption. The quantum dot-hydrotalcite nanomaterials display extremely high stability in mimicking physiological media such as saline serum (pH 5.5) and PBS (pH 7.2). Yet, quantum dot release from the solid structure is noted. In order to prevent the leaking of quantum dots we have developed a novel strategy which consists of using tailor made double layered hydrotalcites as protecting shells for quantum dots embedded into silica nanospheres without changing either the materials or the optical properties.

Size-tunable, hexagonal plate-like Cu3P and Janus-like Cu-Cu3P nanocrystals.

We describe two synthesis approaches to colloidal Cu(3)P nanocrystals using trioctylphosphine (TOP) as phosphorus precursor. One approach is based on the homogeneous nucleation of small Cu(3)P nanocrystals with hexagonal plate-like morphology and with sizes that can be tuned from 5 to 50 nm depending on the reaction time. In the other approach, metallic Cu nanocrystals are nucleated first and then they are progressively phosphorized to Cu(3)P. In this case, intermediate Janus-like dimeric nanoparticles can be isolated, which are made of two domains of different materials, Cu and Cu(3)P, sharing a flat epitaxial interface. The Janus-like nanoparticles can be transformed back to single-crystalline copper particles if they are annealed at high temperature under high vacuum conditions, which makes them an interesting source of phosphorus. The features of the Cu-Cu(3)P Janus-like nanoparticles are compared with those of the striped microstructure discovered more than two decades ago in the rapidly quenched Cu-Cu(3)P eutectic of the Cu-P alloy, suggesting that other alloy/eutectic systems that display similar behavior might give origin to nanostructures with flat, epitaxial interface between domains of two diverse materials. Finally, the electrochemical properties of the copper phosphide plates are studied, and they are found to be capable of undergoing lithiation/delithiation through a displacement reaction, while the Janus-like Cu-Cu(3)P particles do not display an electrochemical behavior that would make them suitable for applications in batteries.

Chemical transformation of Au-tipped CdS nanorods into AuS/Cd core/shell particles by electron beam irradiation.

We demonstrate that electron irradiation of colloidal CdS nanorods carrying Au domains causes their evolution into AuS/Cd core/shell nanoparticles as a result of a concurrent chemical and morphological transformation. The shrinkage of the CdS nanorods and the growth of the Cd shell around the Au tips are imaged in real time, while the displacement of S atoms from the CdS nanorod to the Au domains is evidenced by high-sensitivity energy-dispersive X-ray (EDX) spectroscopy. The various nanodomains display different susceptibility to the irradiation, which results in nanoconfigurations that are very different from those obtained after thermal annealing. Such physical manipulations of colloidal nanocrystals can be exploited as a tool to access novel nanocrystal heterostructures.

Epitaxial CdSe-Au nanocrystal heterostructures by thermal annealing.

The thermal evolution of a collection of heterogeneous CdSe-Au nanosystems (Au-decorated CdSe nanorods, networks, vertical assemblies) prepared by wet-chemical approaches was monitored in situ in the transmission electron microscope. In contrast to interfaces that are formed during kinetically controlled wet chemical synthesis, heating under vacuum conditions results in distinct and well-defined CdSe/Au interfaces, located at the CdSe polar surfaces. The high quality of these interfaces should make the heterostructures more suitable for use in nanoscale electronic devices.

From iron oxide nanoparticles towards advanced iron-based inorganic materials designed for biomedical applications.

In the last decade the progress achieved on the synthesis of inorganic nanostructures has been accompanied by the parallel exploitation of these systems in various fields, among them are biology and medicine. We provide here an overview of the iron-based inorganic nanostructured materials that have been developed and tested in these fields. We will highlight the major concepts on the preparation, physical properties and applications of such nanostructures, starting from the most investigated iron oxide nanoparticles. We will describe then the new generation of inorganic hybrid nanostructures, which are structures that integrate in each nano-object multiple inorganic nanocrystals of different materials. In our discussion we will focus on those works that have provided a sound proof of concept on the potential of the various systems as diagnostic and therapeutic agents.

Magnetic interactions and magnetic anisotropy in exchange coupled 4f-3d systems: a case study of a heterodinuclear Ce3+-Fe3+ cyanide-bridged complex.

We report here a detailed single-crystal EPR and magnetic study of a homologous series of complexes of the type Ln-M (Ln = La(III), Ce(III); M = Fe(III), Co(III)). We were able to obtain a detailed picture of the low-lying levels of Ce(III) and Fe(III) centres through the combined use of single-crystal EPR and magnetic susceptibility data. We show that classical ligand field theory can be of great help in rationalising the energies of the low-lying levels of both the transition-metal and rare-earth ions. The combined analysis of single-crystal EPR and magnetic data of the coupled system Ce-Fe confirmed the great complexity of the interactions involving rare-earth elements. With little uncertainty, it turned out clearly that the description of the interaction involving the lowest lying spin levels requires the introduction of the isotropic, anisotropic and antisymmetric terms.

One-pot synthesis and characterization of size-controlled bimagnetic FePt-iron oxide heterodimer nanocrystals.

A one-pot, two-step colloidal strategy to prepare bimagnetic hybrid nanocrystals (HNCs), comprising size-tuned fcc FePt and inverse spinel cubic iron oxide domains epitaxially arranged in a heterodimer configuration, is described. The HNCs have been synthesized in a unique surfactant environment by temperature-driven sequential reactions, involving the homogeneous nucleation of FePt seeds and the subsequent heterogeneous growth of iron oxide. This self-regulated mechanism offers high versatility in the control of the geometric features of the resulting heterostructures, circumventing the use of more elaborate seeded growth techniques. It has been found that, as a consequence of the exchange coupling between the two materials, the HNCs exhibit tunable single-phase-like magnetic behavior, distinct from that of their individual components. In addition, the potential of the heterodimers as effective contrast agents for magnetic resonance imaging techniques has been examined.

Synthesis, crystal structure, and magnetic studies of oxo-centered trinuclear chromium(III) complexes: [Cr(3)(mu(3)-O)(mu(2)-PhCOO)(6)(H(2)O)(3)]NO(3). 4H(2)O.2CH(3)OH, a case of spin-frustrated system, and [Cr(3)(mu(3)-O)- (mu(2)-PhCOO)(2)(mu(2)-OCH(2)CH(3))(2)(bpy)(2)(NCS )(3)], a new type of [Cr(3)O] core.

The synthesis, crystal structure, and magnetic properties of two trinuclear oxo-centered carboxylate complexes are reported and discussed: [Cr3(mu3-O)(mu2-PhCOO)6(H2O)3]NO3.4H2O.2CH3OH (1) and [Cr3(mu3-O)(mu2-PhCOO)2(mu2-OCH2CH3)2(bpy)2(NCS)3] (2). For both complexes the crystal system is monoclinic, with space group C2/c for 1 and P1/n for 2. The structure of complex 1 consists of discrete trinuclear cations, associated NO3- anions, and lattice methanol and water molecules. The structure of complex 2 is built only by neutral discrete trinuclear entities. The most important feature of 2 is the unusual skeleton of the [Cr3O] core due to the lack of peripheral bridging ligands along one side of the triangular core, which is unique among the structurally characterized (mu3-oxo)trichromium(III) complexes. Magnetic measurements were performed in the 2-300 K temperature range. For complex 1, in the high-temperature region (T > 8 K), experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -2J12S1S2 - 2J13S1S3 - 2J23S2S3 (J12 = J13 = J23) with Jij = -10.1 cm(-1), g = 1.97, and TIP = 550 x 10(-6) emu mol(-1). The antisymmetric exchange interaction plays an important role in the magnetic behavior of the system, so in order to fit the experimental magnetic data at low temperature, a new magnetic model was used where this kind of interaction was also considered. The resulting fitting parameters are the following: Gzz = 0.25 cm(-1), delta = 2.5 cm(-1), and TIP = 550 x 10(-6) emu mol(-1). For complex 2, the experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -2J1(S1S2 + S1S3) - 2J2(S2S3) with J1 = -7.44 cm(-1), J2 = -51.98 cm(-1), and g = 1.99. The magnetization data allows us to deduce the ground term of S = 1/2, characteristic of equilateral triangular chromium(III) for complex 1 and S = 3/2 for complex 2, which is confirmed by EPR measurements.