Amino-phenol complexes of Fe(III) as promising T1 accelerators

Comprehensive Investigation of [Fe(EDTA)]--Functionalized Derivatives and their Supramolecular Adducts with Human Serum Albumin

In recent years, the coordination chemistry of high-spin Fe(III) complexes has increasingly attracted interest due to their potential as effective alternatives to Gd(III)-based MRI contrast agents. This paper discusses the results from our study on Fe(III) complexes with two EDTA derivatives, each modified with either one (EDTA-BOM) or two (EDTA-BOM2) benzyloxymethylene (BOM) groups on the acetic arm(s). These pendant hydrophobic groups enable the complexes to form noncovalent adducts with human serum albumin (HSA), leading to an observed increase in relaxivity due to the reduction in molecular tumbling. Our research involved detailed relaxometric measurements and analyses of both 1H and 17O NMR data at varying temperatures and magnetic field strengths, which is conducted with and without the presence of a protein. A significant finding of this study is the effect of electronic relaxation time on the effectiveness of [Fe(EDTA-BOM)(H2O)]- and [Fe(EDTA-BOM2)(H2O)]- as diagnostic MRI probes. By integrating these relaxometric results with comprehensive thermodynamic, kinetic, and electrochemical data, we have thoroughly characterized how structural modifications to the EDTA base ligand influence the properties of the complexes.

Folate-assisted targeted photocytotoxicity of red-light-activable iron(III) complex co-functionalized gold nanoconjugates (Fe@FA-AuNPs) against HeLa and triple-negative MDA-MB-231 cancer cells

Photo-redox chemistry resulting from ligand to metal charge transfer in red-light-activable iron(III) complexes could be a potent strategic tool for next-generation photochemotherapeutic applications. Herein, we developed an iron(III) complex and folate co-functionalized gold nanoconjugate (Fe@FA-AuNPs) and thoroughly characterized it with NMR, ESI MS, UV-visible, EPR, EDX, XPS, powder X-ray diffraction, TEM and DLS studies. There was a remarkable shift in the SPR band of AuNPs to 680 nm, and singlet oxygen (1O2) and hydroxyl radicals were potently generated upon red-light activation, which were probed by UV-visible and EPR spectroscopic assays. Cellular uptake studies of the nanoconjugate (Fe@FA-AuNPs) revealed significantly higher uptake in folate(+) cancer cells (HeLa and MDA-MB-231) than folate(-) (A549) cancer cells or normal cells (HPL1D), indicating the targeting potential of the nanoconjugate. Confocal imaging indicated primarily mitochondrial localization. The IC50 values of the nanoconjugate determined from a cell viability assay in HeLa, MDA-MB-231, and A549 cells were 27.83, 39.91, and 69.54 μg mL-1, respectively in red light, while in the dark the values were >200 μg mL-1; the photocytotoxicity was correlated with the cellular uptake of the nanoconjugate. The nanocomposite exhibited similar photocytotoxicity (IC50 in red light, 37.35 ± 8.29 μg mL-1 and IC50 in the dark, >200 μg mL-1). Mechanistic studies revealed that intracellular generation of ROS upon red-light activation led to apoptosis in HeLa cells. Scratch-wound-healing assays indicated the inhibition of the migration of MDA-MB-231 cells treated with the nanoconjugate and upon photo-activation. Overall, the nanoconjugate has emerged as a potent tool for next-generation photo-chemotherapeutics in the clinical arena of targeted cancer therapy.

Crystal structure of bis(3,5-dichloro-2-hydroxybenzyl)(2-methoxyethyl)amine

The title compound, systematic name 4,4',6,6'-tetrachloro-2,2'-{[(2-methoxy-ethyl)azanediyl]bis(methylene)}diphenol (C17H17Cl4NO, 1), was prepared via a modified Mannich reaction between 2-meth-oxy-ethyl-amine, 2,4-di-chloro-phenol, and aqueous formaldehyde. The resulting amine bis-(phenol) provides an inter-esting comparison to related species as a result of the electron-withdrawing substituents on the phenol rings, in combination with similar steric parameters. One of the Cl atoms was modeled as a two-component disorder with partial occupancies of 0.49 (3) and 0.51 (3), while the pendant ether group was modeled as a two-component disorder with partial occupancies of 0.867 (3) and 0.133 (3). A comparison of metrical parameters for the title compound and closely related structures provides insight into the use of these species as ligands to support transition-metal complexes for applications as homogeneous catalysts.

Novel Magnetic Elastic Phase-Change Nanodroplets as Dual Mode Contrast Agent for Ultrasound and Magnetic Resonance Imaging

Recently, dual-mode imaging systems merging magnetic resonance imaging (MRI) and ultrasound (US) have been developed. Designing a dual-mode contrast agent is complex due to different mechanisms of enhancement. Herein, we describe novel phase change nanodroplets (PCNDs) with perfluoropentane encapsulated in a pre-polyglycerol sebacate (pre-PGS) shell loaded with polyethylene glycol (PEG)-coated iron oxide nanoparticles as having a dual-mode contrast agent effect. Iron oxide nanoparticles were prepared via the chemical co-precipitation method and PCNDs were prepared via the solvent displacement technique. PCNDs showed excellent enhancement in the in vitro US much more than Sonovue^® microbubbles. Furthermore, they caused a susceptibility effect resulting in a reduction of signal intensity on MRI. An increase in the concentration of nanoparticles caused an increase in the MR contrast effect but a reduction in US intensity. The concentration of nanoparticles in a shell of PCNDs was optimized to obtain a dual-mode contrast effect. Biocompatibility, hemocompatibility, and immunogenicity assays showed that PCNDs were safe and non-immunogenic. Another finding was the dual-mode potential of unloaded PCNDs as T1 MR and US contrast agents. Results suggest the excellent potential of these PCNDs for use as dual-mode contrast agents for both MRI and US.

Facile synthesis of biocompatible magnetic titania nanorods for T1-magnetic resonance imaging and enhanced phototherapy of cancers

Cancer treatment has been recently energized by nanomaterials that simultaneously offer diagnostic and therapeutic effects. Among the imaging and treatment modalities in frontline research today, magnetic resonance imaging (MRI) and phototherapy have gained significant interest due to their noninvasiveness among other intriguing benefits. Herein, Fe(iii) was adsorbed on titanium dioxide to develop magnetic Fe-TiO₂ nanocomposites (NCs) which leverage the Fe moiety in a double-edge-sword approach to: (i) achieve T₁-weighted MRI contrast enhancement, and (ii) improve the well-established photodynamic therapeutic efficacy of TiO₂ nanoparticles. Interestingly, the proposed NCs exhibit classic T₁ MRI contrast agent properties (r₁ = 1.16 mM^-1 s^-1) that are comparable to those of clinically available contrast agents. Moreover, the NCs induce negligible cytotoxicity in traditional methods and show remarkable support to the proliferation of intestine organoids, an advanced toxicity evaluation system based on three-dimensional organoids, which could benefit their potential safe application for in vivo cancer theranostics. Aided by the Fenton reaction contribution of the Fe component of the Fe-TiO₂ NCs, considerable photo-killing of cancer cells is achieved upon UV irradiation at very low (2.5 mW cm^-2) intensity in typical cancer PDT. It is therefore expected that this study will guide the engineering of other biocompatible magnetic titania-based nanosystems with multi-faceted properties for biomedical applications.

A step towards gadolinium-free bioresponsive MRI contrast agent

The last 30 years of gadolinium-based "static" MRI contrast agents motivated to investigate bioresponsive agents with endogenous paramagnets. Iron(III) chelated by N,O-aminophenol skeleton of high versatility, and tuning potential was studied. The two-step convenient route of the ligand is characterized by high selectivity and allows for building a tunable chelate system. Functionalization with galactose endows a bioresponsive character sensitive to the enzyme activity. Direct relaxometric measurements of the resulting complexes revealed extremely high relaxivity of 5.62 mmol/dm³·s^-1 comparable to classic gadolinium complexes. Enzymatic hydrolysis leads to relaxivity change by over 80%. Phantom MRI studies prove the bioresponsive character by contras percentage change within the range 40-275%. Cytotoxicity studies showed 70-90% viability of HeLa cells of the iron complexes. Proposed iron-based chelates with galactosidase-sensitive fragment express unequivocal relaxivity and MRI contras change and good biocompatibility. Therefore, these complexes are a promising step towards modern, bioresponsive MRI contrast agents with a "human-friendly" metal.

Multiwalled carbon nanotube hybrids as MRI contrast agents

Magnetic resonance imaging (MRI) is one of the most commonly used tomography techniques in medical diagnosis due to the non-invasive character, the high spatial resolution and the possibility of soft tissue imaging. Contrast agents, such as gadolinium complexes and superparamagnetic iron oxides, are administered to spotlight certain organs and their pathologies. Many new models have been proposed that reduce side effects and required doses of these already clinically approved contrast agents. These new candidates often possess additional functionalities, e.g., the possibility of bioactivation upon action of particular stimuli, thus serving as smart molecular probes, or the coupling with therapeutic agents and therefore combining both a diagnostic and therapeutic role. Nanomaterials have been found to be an excellent scaffold for contrast agents, among which carbon nanotubes offer vast possibilities. The morphology of multiwalled carbon nanotubes (MWCNTs), their magnetic and electronic properties, the possibility of different functionalization and the potential to penetrate cell membranes result in a unique and very attractive candidate for a new MRI contrast agent. In this review we describe the different issues connected with MWCNT hybrids designed for MRI contrast agents, i.e., their synthesis and magnetic and dispersion properties, as well as both in vitro and in vivo behavior, which is important for diagnostic purposes. An introduction to MRI contrast agent theory is elaborated here in order to point to the specific expectations regarding nanomaterials. Finally, we propose a promising, general model of MWCNTs as MRI contrast agent candidates based on the studies presented here and supported by appropriate theories.