Designing lanthanide coordination nanoframeworks as X-ray responsive radiosensitizers for efficient cancer therapy

A series of three-dimensional Ln-based coordination nanoframeworks were designed and shown potential as efficient and low toxic X-ray responsive radiosensitizers for the treatment of cervical cancer.

Development of a tumor-targetable heteropolymetallic lanthanide-complex-based magnetoluminescent probe for dual-modal time-gated luminescence/magnetic resonance imaging of cancer cells in vitro and in vivo

Multifunctional heteropolymetallic lanthanide-complex-based magnetoluminescent probe for tumor-targeting TGL/MR imaging in vitro and in vivo.

Macrocyclic Chelates Bridged by a Diaza-Crown Ether: Towards Multinuclear Bimodal Molecular Imaging Probes

Bridged polymacrocyclic ligands featured by structurally different cages offer the possibility of coordinating multiple trivalent lanthanide ions, giving rise to the exploitation of their different physicochemical properties, e.g., multimodal detection for molecular imaging purposes. Intrigued by the complementary properties of optical and MR-based image capturing modalities, we report the synthesis and characterization of the polymetallic Ln(III)-based chelate comprised of two DOTA-amide-based ligands (DOTA—1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) bridged via 1,10-diaza-18-crown-6 (DA18C6) motif. The DOTA-amide moieties and the DA18C6 were used to chelate two Eu(III) ions and one Tb(III) ion, respectively, resulting in a multinuclear heterometallic complex Eu₂LTb. The bimetallic complex without Tb(III), Eu₂L, displayed a strong paramagnetic chemical exchange saturation transfer (paraCEST) effect. Notably, the luminescence spectra of Eu₂LTb featured mixed emission including the characteristic bands of Eu(III) and Tb(III). The advantageous features of the complex Eu₂LTb opens new possibilities for the future design of bimodal probes and their potential applicability in CEST MR and optical imaging.

Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist

Advances in optical microscopy are continually narrowing the chasm in our appreciation of biological organization between the molecular and cellular levels, but many practical problems are still limiting. Observation is always limited by the rapid dynamics of ultrastructural modifications of intracellular components, and often by cell motility: imaging of the unicellular protist parasite of ornamental fish, Spironucleus vortens, has proved challenging. Autofluorescence of nicotinamide nucleotides and flavins in the 400-580 nm region of the visible spectrum, is the most useful indicator of cellular redox state and hence vitality. Fluorophores emitting in the red or near-infrared (i.e., phosphors) are less damaging and more penetrative than many routinely employed fluors. Mountants containing free radical scavengers minimize fluorophore photobleaching. Two-photon excitation provides a small focal spot, increased penetration, minimizes photon scattering and enables extended observations. Use of quantum dots clarifies the competition between endosomal uptake and exosomal extrusion. Rapid motility (161 μm/s) of the organism makes high resolution of ultrastructure difficult even at high scan speeds. Use of voltage-sensitive dyes determining transmembrane potentials of plasma membrane and hydrogenosomes (modified mitochondria) is also hindered by intracellular motion and controlled anesthesia perturbs membrane organization. Specificity of luminophore binding is always questionable; e.g. cationic lipophilic species widely used to measure membrane potentials also enter membrane-bounded neutral lipid droplet-filled organelles. This appears to be the case in S. vortens, where Coherent Anti-Stokes Raman Scattering (CARS) micro-spectroscopy unequivocally images the latter and simultaneous provides spectral identification at 2840 cm^-1. Secondary Harmonic Generation highlights the highly ordered structure of the flagella.

A Water-Soluble Tetraazaperopyrene Dye as Strong G-Quadruplex DNA Binder

The interactions of the water-soluble tetraazaperopyrene dye 1 with ct-DNA, duplex-[(dAdT)12 ⋅(dAdT)12 ], duplex-[(dGdC)12 ⋅(dGdC)12 ] as well as with two G-quadruplex-forming sequences, namely the human telomeric 22AG and the promotor sequence c-myc, were investigated by means of UV/visible and fluorescence spectroscopy, isothermal titration calorimetry (ITC) and molecular docking studies. Dye 1 exhibits a high affinity for G-quadruplex structures over duplex DNA structures. Furthermore, the ligand shows promising G-quadruplex discrimination, with an affinity towards c-myc of 2×10(7)  m(-1) (i.e., Kd =50 nm), which is higher than for 22AG (4×10(6)  m(-1) ). The ITC data reveal that compound 1 interacts with c-myc in a stoichiometric ratio of 1:1 but also indicate the presence of two identical lower affinity secondary binding sites per quadruplex. In 22AG, there are two high affinity binding sites per quadruplex, that is, one on each side, with a further four weaker binding sites. For both quadruplex structures, the high affinity interactions between compound 1 and the quadruplex-forming nucleic acid structures are weakly endothermic. Molecular docking studies suggest an end-stacking binding mode for compound 1 interacting with quadruplex structures, and a higher affinity for the parallel conformation of c-myc than for the mixed-hybrid conformation of 22AG. In addition, docking studies also suggest that the reduced affinity for duplex DNA structures is due to the non-viability of an intercalative binding mode.

Tri- and tetranuclear RuII–GdIII2 and RuII–GdIII3 d–f heterometallic complexes as potential bimodal imaging probes for MRI and optical imaging

Tri- and tetranuclear Ru^II–GdII2 and Ru^II–GdIII3 d–f heterometallic complexes, which function as contrast agents for MRI and as optical probes for fluorescence imaging, are reported. In vitro studies using the HeLa cell lines show that these complexes exhibit anticancer activity.

Near-IR luminescent lanthanide complexes with 1,8-diaminoanthraquinone-based chromophoric ligands

1,8-Anthraquinone derivatives can act as low energy, visible light sensitizers for near-IR emitting lanthanides.

Synthesis, relaxivity, and in vitro fluorescence imaging studies of a novel d-f heterometallic trinuclear complex as a potential bimodal imaging probe for MRI and optical imaging

A new trinuclear heterometallic Ru(II)-Gd complex of 4-aminopyridine appended DO3A (DO3A = 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane) with 2,2'-bipyridine as ancillary ligands is synthesized and its relaxometry and in vitro fluorescence imaging studies are reported. The complex [Ru(bpy)2{Gd(DOTA-AMpy)(H2O)}2]Cl2 (7) exhibits a "per Gd" longitudinal relaxivity (r1p) of 5.80 and 14.30 mM(-1) s(-1) in aqueous solution and in the presence of HSA, respectively (20 MHz, pH = 7.4, PBS, 37 °C). The complex 7 exhibits an intense (1)MLCT absorption band at 480 nm and luminesces at 595 nm with a luminescence quantum yield of 3.2%. The fluorescence microscopy imaging study of HeLa cells incubated with 7 and stained with ethidium bromide and acridine orange confirms that the cells are viable throughout the imaging experiments and its cytotoxicity against HeLa cells, studied by the MTT assay, demonstrates its use for bioimaging studies. HeLa cell lines treated with the complex 7 and stained with Hoechst-33342 showed marked morphological signs of apoptosis in a dose-dependent manner by inducing changes in cell cycle arrest at the G2/M phase. Furthermore, apoptosis of HeLa cells, studied by the DNA ladder assay, indicates apoptotic cell death lending support for the antitumor activity of 7. A molecular docking study reveals that the complex 7 intercalates into the major groove of the DNA stabilized by hydrogen bonding and it binds with HSA by electrostatic- and hydrogen bonding interactions. The relaxometry, luminescence and fluorescence imaging studies indicate that the Ru(II)-Gd complex 7 has a good cell membrane permeability and could be considered as a potential bimodal imaging probe.

Using lanthanide ions in molecular bioimaging

This review presents an accessible discussion of the application of trivalent lanthanide ions in both optical and magnetic resonance imaging.

Imaging agents based on lanthanide doped nanoparticles

This review summarizes the recent progress of single and multimodal imaging agents based on lanthanide doped nanoparticles.

Recent advances in Gd-chelate based bimodal optical/MRI contrast agents

Recent developments in the field of bimodal MRI/optical contrast agents, based on Gd³⁺-chelates are presented.

Towards polymetallic lanthanide complexes as dual contrast agents for magnetic resonance and optical imaging

In the spotlight: polymetallic complexes permitting efficient sensitization of lanthanide luminescence and exhibiting favorable relaxometric properties.