Nanoscale coordination polymers exhibiting luminescence properties and NMR relaxivity

Post-synthetic modification of Prussian blue type nanoparticles: tailoring the chemical and physical properties

This review focuses on recent advances in the post-synthetic modification of nano-sized Prussian blue and its analogues and compares them with the current strategies used in metal–organic frameworks to give future outlooks in this field.

A rational study of the influence of Mn2+-insertion in Prussian blue nanoparticles on their photothermal properties

We investigated a series of Mn²⁺-Prussian blue (PB) nanoparticles Na_zMn_xFe_1-x[Fe(CN)₆]_1-y□y·nH₂O of similar size, surface state and cubic morphology with various amounts of Mn²⁺ synthesized through a one step self-assembly reaction. We demonstrated by a combined experimental-theoretical approach that during the synthesis, Mn²⁺ substituted Fe³⁺ up to a Mn/Na-Mn-Fe ratio of 32 at% in the PB structure, while for higher amounts, the Mn₂[Fe(CN)₆] analogue is obtained. For comparison, the post-synthetic insertion of Mn2+ in PB nanoparticles was also investigated and completed with Monte-Carlo simulations to probe the plausible adsorption sites. The photothermal conversion efficiency (η) of selected samples was determined and showed a clear dependence on the Mn²⁺amount with a maximum efficiency for a Mn/Na-Mn-Fe ratio of 10 at% associated with a dependence on the nanoparticle concentration. Evaluation of the in vitro photothermal properties of these nanoparticles performed on triple negative human breast adenocarcinoma (MDA-MB-231) cells by using continuous and pulsed laser irradiation confirm their excellent PTT efficiency permitting low dose use.

K2 Mn3 [FeII (CN)6 ]2 NPs with High T1 -Relaxivity Attributable to Water Coordination on the Mn(II) Center for Gastrointestinal Tract MR Imaging

The lack of acid stability in the stomach and of temporal stability when moving through the gastrointestinal (GI) tract has made the development of oral magnetic resonance imaging (MRI) contrast agents based on the platform of Gd³⁺ -complexes problematic.On the other hand, the negative contrast enhancement produced by the T₂ -weighted magnetic metal oxide nanoparticles (NPs) often renders the image readout difficult. Biocompatible NPs of the manganese Prussian blue analog K₂ Mn₃ [Fe^II (CN)₆ ]₂ exhibit extremely high stability under the acidic conditions of the gastric juice. Additionally, the high r₁ relaxivity, low toxicity, and high temporal stability of such NPs offer great potential for the development of a true T₁ -weighted oral contrast agent for MRI of the entire GI tract.

Octacyanidometallates for multifunctional molecule-based materials

Octacyanidometallates have been successfully employed in the design of heterometallic coordination systems offering a spectacular range of desired physical properties with great potential for technological applications. The [M(CN)8]n- ions comprise a series of complexes of heavy transition metals in high oxidation states, including NbIV, MoIV/V, WIV/V, and ReV. Since the discovery of the pioneering bimetallic {MnII4[MIV(CN)8]2} and {MnII9[MV(CN)8]6} (M = Mo, W) molecules in 2000, octacyanidometallates were fruitfully explored as precursors for the construction of diverse d-d or d-f coordination clusters and frameworks which could be obtained in the crystalline form under mild synthetic conditions. The primary interest in [M(CN)8]n--based networks was focused on their application as molecule-based magnets exhibiting long-range magnetic ordering resulting from the efficient intermetallic exchange coupling mediated by cyanido bridges. However, in the last few years, octacyanidometallate-based materials proved to offer varied and remarkable functionalities, becoming efficient building blocks for the construction of molecular nanomagnets, magnetic coolers, spin transition materials, photomagnets, solvato-magnetic materials, including molecular magnetic sponges, luminescent magnets, chiral magnets and photomagnets, SHG-active magnetic materials, pyro- and ferroelectrics, ionic conductors as well as electrochemical containers. Some of these materials can be processed into the nanoscale opening the route towards the development of magnetic, optical and electronic devices. In this review, we summarise all important achievements in the field of octacyanidometallate-based functional materials, with the particular attention to the most recent advances, and present a thorough discussion on non-trivial structural and electronic features of [M(CN)8]n- ions, which are purposefully explored to introduce desired physical properties and their combinations towards advanced multifunctional materials.

Fashioning Prussian Blue Nanoparticles by Adsorption of Luminophores: Synthesis, Properties, and in Vitro Imaging

We report the postsynthetic functionalization of Prussian blue (PB) nanoparticles by two different luminophores (2-aminoanthracene and rhodamine B). We show that the photoluminescence properties of the fluorophores are modified by a confinement effect upon adsorption and demonstrate that such multifunctional nanosized systems could be used for in vitro imaging.

TbIII/3d–TbIII clusters derived from a 1,4,7-triazacyclononane-based hexadentate ligand with field-induced slow magnetic relaxation and oxygen-sensitive luminescence

A family of new Tb^III/3d–Tb^III cluster complexes based on N,N′,N′′-tris(3,5-dimethyl-2-hydroxybenzyl)-1,4,7-triazacyclononane have been synthesized and they exhibit interesting magnetic and luminescent properties.

Multifunctional manganese-doped Prussian blue nanoparticles for two-photon photothermal therapy and magnetic resonance imaging

Here we demonstrate for the first time that Mn²⁺-doped Prussian blue nanoparticles of c.a. 70 nm act as effective agents for photothermal therapy under two-photon excitation with an almost total eradication of malignant cells (97 and 98%) at a concentration of 100 μg mL^-1 24 h after NIR excitation. This effect combined with interesting longitudinal NMR relaxivity values offer new perspectives for effective imaging and cancer treatment.

Nanoparticles of gadolinium-incorporated Prussian blue with PEG coating as an effective oral MRI contrast agent for gastrointestinal tract imaging

Biocompatible nanoparticles of gadolinium-incorporated Prussian blue with the empirical formula K(0.94)Gd(0.02)Fe[Fe(CN)6] exhibit extremely high stability against the release of Gd(3+) and CN(-) ions under the acidic conditions similar to stomach juice. The high r1 relaxivity, low cytotoxicity and the ability of such nanoparticles to penetrate the cell membrane suggest that this coordination-polymer structural platform offers a unique opportunity for developing the next generation of T1-weighted oral cellular MRI probes for the early detection of tumors in the gastrointestinal tract.

201Tl-labeled Prussian blue and Au@Prussian blue nanoprobes for SPEC-CT imaging: influence of the size, shape and coating on the biodistribution

²⁰¹Tl-labeled Prussian blue and core@shell Au@Prussian blue nanoparticles coated with the phospholipidic bilayer and dextran were investigated in vivo as nanoprobes by usingSPECT-CT scintigraphy.

Prussian blue type nanoparticles for biomedical applications

Prussian blue type nanoparticles are exciting nano-objects that combine the advantages of molecule-based materials and nanochemistry. Here we provide a short overview focalizing on the recent advances of these nano-objects designed for biomedical applications and give an outlook on the future research orientations in this domain.

Ultrasmall inorganic nanoparticles: State-of-the-art and perspectives for biomedical applications

Ultrasmall nanoparticulate materials with core sizes in the 1-3nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications. This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.

Immobilization of Metal Hexacyanoferrate Ion-Exchangers for the Synthesis of Metal Ion Sorbents--A Mini-Review

Metal hexacyanoferrates are very efficient sorbents for the recovery of alkali and base metal ions (including radionuclides such as Cs). Generally produced by the direct reaction of metal salts with potassium hexacyanoferrate (the precursors), they are characterized by ion-exchange and structural properties that make then particularly selective for Cs(I), Rb(I) and Tl(I) recovery (based on their hydrated ionic radius consistent with the size of the ion-exchanger cage), though they can bind also base metals. The major drawback of these materials is associated to their nanometer or micrometer size that makes them difficult to recover in large-size continuous systems. For this reason many techniques have been designed for immobilizing these ion-exchangers in suitable matrices that can be organic (mainly polymers and biopolymers) or inorganic (mineral supports), carbon-based matrices. This immobilization may proceed by in situ synthesis or by entrapment/encapsulation. This mini-review reports some examples of hybrid materials synthesized for the immobilization of metal hexacyanoferrate, the different conditionings of these composite materials and, briefly, the parameters to take into account for their optimal design and facilitated use.

Photosensitizer-Conjugated Albumin-Polypyrrole Nanoparticles for Imaging-Guided In Vivo Photodynamic/Photothermal Therapy

Conjugated polymers with strong absorbance in the near-infrared (NIR) region have been widely explored as photothermal therapy agents due to their excellent photostability and high photothermal conversion efficiency. Herein, polypyrrole (PPy) nanoparticles are fabricated by using bovine serum albumin (BSA) as the stabilizing agent, which if preconjugated with photosensitizer chlorin e6 (Ce6) could offer additional functionalities in both imaging and therapy. The obtained PPy@BSA-Ce6 nanoparticles exhibit little dark toxicity to cells, and are able to trigger both photodynamic therapy (PDT) and photothermal therapy (PTT). As a fluorescent molecule that in the meantime could form chelate complex with Gd(3+), Ce6 in PPy@BSA-Ce6 nanoparticles after being labeled with Gd(3+) enables dual-modal fluorescence and magnetic resonance (MR) imaging, which illustrate strong tumor uptake of those nanoparticles after intravenous injection into tumor-bearing mice. In vivo combined PDT and PTT treatment is then carried out after systemic administration of PPy@BSA-Ce6, achieving a remarkably improved synergistic therapeutic effect compared to PDT or PTT alone. Hence, a rather simple one-step approach to fabricate multifunctional nanoparticles based on conjugated polymers, which appear to be promising in cancer imaging and combination therapy, is presented.

Investigation of cyano-bridged coordination nanoparticles Gd(3+)/[Fe(CN)6](3-)/D-mannitol as T1-weighted MRI contrast agents

Cyano-bridged Gd(3+)/[Fe(CN)6](3-) coordination polymer nanoparticles of 3-4 nm stabilized with D-mannitol presenting a high r1 relaxivity value of 11.4 mM(-1) s(-1) were investigated in vivo as contrast agents (CA) for Magnetic Resonance Imaging (MRI). They allow an increase of the MR image contrast and can act as an efficient intravascular T1 CA with a relatively long blood-circulation lifetime (60 min) without specific toxicity.

Selective ion exchange governed by the Irving-Williams series in K2Zn3[Fe(CN)6]2 nanoparticles: toward a designer prodrug for Wilson's disease

The principle of the Irving-Williams series is applied to the design of a novel prodrug based on K2Zn3[Fe(CN)6]2 nanoparticles (ZnPB NPs) for Wilson's disease (WD), a rare but fatal genetic disorder characterized by the accumulation of excess copper in the liver and other vital organs. The predetermined ion-exchange reaction rather than chelation between ZnPB NPs and copper ions leads to high selectivity of such NPs for copper in the presence of the other endogenous metal ions. Furthermore, ZnPB NPs are highly water-dispersible and noncytotoxic and can be readily internalized by cells to target intracellular copper ions for selective copper detoxification, suggesting their potential application as a new-generation treatment for WD.

²⁰¹Tl⁺-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy

Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive (201)Tl(+) to obtain new nanoprobes as radiotracers for 201-thallium-based imaging.

Biocompatible nanoparticles of KGd(H₂O)₂[Fe(CN)₆]·H₂O with extremely high T₁-weighted relaxivity owing to two water molecules directly bound to the Gd(III) center

A simple one-step method for preparing biocompatible nanoparticles of gadolinium ferrocyanide coordination polymer KGd(H2O)2[Fe(CN)6]·H2O is reported. The crystal structure of this coordination polymer is determined by X-ray powder diffraction using the bulk materials. The stability, cytotoxicity, cellular uptake, and MR phantom and cellular imaging studies suggest that this coordination-polymer structural platform offers a unique opportunity for developing the next generation of T1-weighted contrast agents with high relaxivity as cellular MR probes for biological receptors or markers. Such high-relaxivity MR probes may hold potential in the study of molecular events and may be used for in vivo MR imaging in biomedical research and clinical applications.

MnII-containing coordination nanoparticles as highly efficient T1 contrast agents for magnetic resonance imaging

Nanoparticles of Mn^II-containing Prussian blue analogues reveal large longitudinal relaxivities exceeding that of clinical contrast agents.

Paramagnetic Nanocrystals: Remarkable Lanthanide-Doped Nanoparticles with Varied Shape, Size, and Composition

Magnetic nanoparticles have been developed in recent years with applications in unique and crucial areas such as biomedicine, data storage, environmental remediation, catalysis, and so forth. NaYF4 nanoparticles were synthesized and isolated with lanthanide dopant percentages, confirmed by ICP-OES measurements, of Er, Yb, Tb, Gd, and Dy that were in agreement with the targeted ratios. SEM images showed a distinct variation in particle size and shape with dopant type and percentage. HRTEM and XRD studies confirmed the particles to be crystalline, possessing both α and β phases. Magnetic measurements determined that all of the nanoparticles were paramagnetic and did not exhibit a blocking temperature from 2 to 300 K. The multifunctional properties of these nanoparticles make them suitable for many applications, such as multimodal imaging probes, up-conversion fluorescent markers, as well as MRI contrast agents.