Optimizing sensitization processes in dinuclear luminescent lanthanide oligomers: selection of rigid aromatic spacers.

This work illustrates a simple approach for optimizing the lanthanide luminescence in molecular dinuclear lanthanide complexes and identifies a particular multidentate europium complex as the best candidate for further incorporation into polymeric materials. The central phenyl ring in the bis-tridentate model ligands L3­L5, which are substituted with neutral (X = H, L3), electron-withdrawing (X = F, L4), or electron-donating (X = OCH3, L5) groups, separates the 2,6-bis(benzimidazol-2-yl)pyridine binding units of linear oligomeric multi-tridentate ligand strands that are designed for the complexation of luminescent trivalent lanthanides, Ln(III). Reactions of L3­L5 with [Ln(hfac)3(diglyme)] (hfac­ is the hexafluoroacetylacetonate anion) produce saturated single-stranded dumbbell-shaped complexes [Ln2(Lk)(hfac)6] (k = 3­5), in which the lanthanide ions of the two nine-coordinate neutral [N3Ln(hfac)3] units are separated by 12­14 Å. The thermodynamic affinities of [Ln(hfac)3] for the tridentate binding sites in L3­L5 are average (6.6 ≤ log(ß(2,1)(Y,Lk)) ≤ 8.4) but still result in 15­30% dissociation at millimolar concentrations in acetonitrile. In addition to the empirical solubility trend found in organic solvents (L4 > L3 >> L5), which suggests that the 1,4-difluorophenyl spacer in L4 is preferable, we have developed a novel tool for deciphering the photophysical sensitization processes operating in [Eu2(Lk)(hfac)6]. A simple interpretation of the complete set of rate constants characterizing the energy migration mechanisms provides straightforward objective criteria for the selection of [Eu2(L4)(hfac)6] as the most promising building block.

Delivery of thymoquinone through hyaluronic acid-decorated mixed Pluronic® nanoparticles to attenuate angiogenesis and metastasis of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic subtype of breast cancer showing non-responsiveness to most available therapeutic options. Therefore, smart therapeutic approaches to selectively transport and target TNBCs are required. Herein, we developed thymoquinone (TQ)-loaded, hyaluronic acid (HA)-conjugated Pluronic® P123 and F127 copolymer nanoparticles (HA-TQ-Nps) as a selective drug-carrying vehicle to deliver anticancer phytochemical TQ to TNBC cells. The mean size of nanoparticles was around 19.3 ± 3.2 nm. and they were stable at room temperature up to 4 months. HA-TQ-Nps were immensely cytotoxic towards TNBC cells but did not show the toxic effect on normal cells. Detailed investigations also demonstrated its pro-apoptotic, anti-metastatic and anti-angiogenic activity. In-depth mechanistic studies highlighted that HA-TQ-Nps retarded cell migration of TNBC cells through up-regulation of microRNA-361 which in turn down-regulated Rac1 and RhoA mediated cell migration and also perturbed the cancer cell migration under the influence of the autocrine effect of VEGF-A. Moreover, HA-TQ-Np-treatment also perturbed tumor-induced vascularization by reducing the secretion of VEGF-A. The anti-metastatic and anti-angiogenic activity of HA-TQ-Nps was found to be evident in both MDA-MB-231 xenograft chick embryos and 4T1-mammary solid tumor model in syngeneic mice. Thus, an innovative targeted nano-therapeutic approach is being established to reduce the tumor burden and inhibit metastasis and angiogenesis simultaneously for better management of TNBC.