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

Docking and in vitro molecular biology studies of p-anisidine-appended 1-hydroxy-2-acetonapthanone Schiff base lanthanum(iii) complexes

A new series of lanthanum(iii) complexes was synthesized using a p-anisidine-appended 1-hydroxy-2-acetonapthanone (3) Schiff base and characterized via spectroscopic methods. The ligand was synthesized via sonication and the crystalline product was characterized using X-ray crystallography. The genotoxicity of the compound was assessed primarily by the bacterial reverse mutation (Ames) test and the in vitro mammalian chromosome aberration test; in both cases, the samarium complex 5 was found to be non-mutagenic. The anti-tumor activity of complexes 4, 5, and 6 was assayed against HeLa tumor cells and screened using the MTT assay. The IC50 value of complex 5 was found to be 34 ± 1.2 μg mL-1 and this compound exhibited superior activity towards the cells compared to 4 and 6. These results were further confirmed by Hoechst 33258 staining and AO/EI dual staining, which indicated that the cells underwent an apoptosis mechanism in a dose-dependent manner. The apoptosis was further confirmed by the formation of ladders in the DNA fragmentation assay, and the western blot analysis of complex 5 suggested that the cells underwent the caspase-3-dependent pathway with PARP cleavage. Furthermore, the docking studies of complex 5 with HSA showed that it was situated in a hydrophilic cavity held by the electrostatic attraction of four hydrogen-bonding interactions. PDB ID:1BNA binds with complex 5via strong π-π stacking interactions, which facilitate binding with the major grooves of DNA strands. The above-mentioned results illustrate that for complex 5, mitochondrion-mediated apoptosis occurs via caspase-3 activation. Complex 5 binds with DNA via intercalation because of S-phase cell cycle arrest in the HeLa cells.

Pharmacokinetics and biodistribution study of self-assembled Gd-micelles demonstrating blood-pool contrast enhancement for MRI

Magnetic resonance angiography (MRA) requires the use of contrast agents (CAs) to enable accurate diagnosis. There are currently no CAs on the market with appropriate pharmacokinetic (PK) parameters, namely long persistence in the blood, that can be easily used for MRA. We have recently synthesized amphiphilic building blocks loaded with gadolinium (Gd), which self-assemble into Gd-micelles in aqueous media, and have evaluated their potential as a blood-pool contrast agent (BPCA) in vivo. To assess the short and long term PK of Gd-micelles, the blood and organs of the mice were analyzed at t = 30 min, 1, 2, 3 h, 7, 14 and 21 days. Gd-DOTA was used as a control because it is the gold-standard CA for MRA despite its rapid clearance from the blood compartment. Gd-micelles circulated in the blood for more than 3 h postinjection whereas Gd-DOTA was eliminated less than half an hour postinjection. No side effects were observed in the mice up to the end of the study at 21 days and no accumulation of Gd was observed in the brain or bones. The Magnetic Resonance Imaging (MRI) parameters and the results of this in vivo study indicate the true BCPA properties of Gd-micelles and warrant further development.

Bimetallic titanocene-gold phosphane complexes inhibit invasion, metastasis, and angiogenesis-associated signaling molecules in renal cancer

Following promising recent in vitro and in vivo studies of the anticancer efficacies of heterometallic titanocene-gold chemotherapeutic candidates against renal cancer, we report here on the synthesis, characterization, stability studies and biological evaluation of a new titanocene complex containing a gold-triethylphosphane fragment [(η-C₅H₅)₂TiMe(μ-mba)Au(PEt₃)] (4) Titanofin. The compound is more stable in physiological fluid than those previously reported, and it is highly cytotoxic against a line of human clear cell renal carcinoma. We describe here preliminary mechanistic data for this compound and previously reported [(η-C₅H₅)₂TiMe(μ-mba)Au(PPh₃)] (2) Titanocref which displayed remarkable activity in an in vivo mouse model. Mechanistic studies were carried out in the human clear cell renal carcinoma Caki-1 line for the bimetallic compounds [(η-C₅H₅)₂TiMe(μ-mba)Au(PR₃)] (PR₃ = PPh₃2 Titanocref and PEt₃4 Titanofin), the two monometallic gold derivatives [Au(Hmba)(PR₃)] (PR₃ = PPh₃1 cref; PEt₃3 fin), titanocene dichloride and Auranofin as controls. These studies indicate that bimetallic compounds Titanocref (2) and Titanofin (4) are more cytotoxic than gold monometallic derivatives (1 and 3) and significantly more cytotoxic than titanocene dichloride while being quite selective. Titanocref (2) and Titanofin (4) inhibit migration, invasion, and angiogenic assembly along with molecular markers associated with these processes such as prometastatic IL(s), MMP(s), TNF-α, and proangiogenic VEGF, FGF-basic. The bimetallic compounds also strongly inhibit the mitochondrial protein TrxR often overexpressed in cancer cells evading apoptosis and also inhibit FOXC2, PECAM-1, and HIF-1α whose overexpression is linked to resistance to genotoxic chemotherapy. In summary, bimetallic titanocene-gold phosphane complexes (Titanocref 2 and Titanofin 4) are very promising candidates for further preclinical evaluations for the treatment of renal cancer.

A heterometallic ruthenium-gold complex displays antiproliferative, antimigratory, and antiangiogenic properties and inhibits metastasis and angiogenesis-associated proteases in renal cancer

Heterobimetallic compounds are designed to harness chemotherapeutic traits of distinct metal species into a single molecule. The ruthenium-gold (Ru-Au) family of compounds based on Au-N-heterocyclic carbene (NHC) fragments [Cl2(p-cymene)Ru(μ-dppm)Au(NHC)]ClO4 was conceived to combine the known antiproliferative and cytotoxic properties of Au-NHC-based compounds and the antimigratory, antimetastatic, and antiangiogenic characteristic of specific Ru-based compounds. Following recent studies of the anticancer efficacies of these Ru-Au-NHC complexes with promising potential as chemotherapeutics against colorectal, and renal cancers in vitro, we report here on the mechanism of a selected compound, [Cl2(p-cymene)Ru(μ-dppm)Au(IMes)]ClO4 (RANCE-1, 1). The studies were carried out in vitro using a human clear cell renal carcinoma cell line (Caki-1). These studies indicate that bimetallic compound RANCE-1 (1) is significantly more cytotoxic than the Ru (2) or Au (3) monometallic derivatives. RANCE-1 significantly inhibits migration, invasion, and angiogenesis, which are essential for metastasis. RANCE-1 was found to disturb pericellular proteolysis by inhibiting cathepsins, and the metalloproteases MMP and ADAM which play key roles in the etiopathogenesis of cancer. RANCE-1 also inhibits the mitochondrial protein TrxR that is often overexpressed in cancer cells and facilitates apoptosis evasion. We found that while auranofin perturbed migration and invasion to similar degrees as RANCE-1 (1) in Caki-1 renal cancer cells, RANCE-1 (1) inhibited antiangiogenic formation and VEGF expression. We found that auranofin and RANCE-1 (1) have distinct proteolytic profiles. In summary, RANCE-1 constitutes a very promising candidate for further preclinical evaluations in renal cancer.

Lipid Extracts from the Brains of Silver Carp (Hypophthalmichthys molitrix) Induce Apoptosis in MCF-7 Cells through the Generation of Reactive Oxygen Species and the Mitochondrial Pathway

Previous studies have verified the protective role of n3 polyunsaturated fatty acids (PUFAs) in cancer. Fish brain lipids are rich in n3 PUFAs. However, the action and mechanism of their potent anticancer activities remain unclear. In this study, polar lipids (PLs) and neutral lipids (NLs) were isolated from the total lipids (TLs) of the silver carp brain, and the anticancer effects of the lipid fractions (LFs) were examined in a human breast cancer cell line (MCF-7). The LFs effectively inhibited the cell proliferation of MCF-7 cells in a time- and concentration-dependent manner by cell cycle arrest at the S stage and induction of apoptosis. Further analyses showed that the apoptotic effect of the LFs on MCF-7 cells was associated with the accumulation of elevated levels of reactive oxygen species and the loss of mitochondrial membrane potential. Among the TLs, PLs were more effective at causing breast cancer cell death than NLs. Our study showed that the LFs from silver carp brains may aid the prevention and treatment of human breast cancer.

Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe

A new Gadolinium(III)-coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F-) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid (CA) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd-CA, the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity (r₁). The fluorescent detection limit for fluoride ions was determined to be 8 μM based on a 3σ/slope. The desirable features of the proposed DO3A-Gd-CA, such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd-CA could be potentially used in biomedical diagnosis fields.

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.

Fluoride-specific fluorescence/MRI bimodal probe based on a gadolinium(iii)–flavone complex: synthesis, mechanism and bioimaging application in vivo

The present work reports a bimodal probe for the fluorescence and magnetic resonance detection of fluoride ion (F⁻) in aqueous medium andin vivo.