On the Aqueous Solution Behavior of C-Substituted 3,1,2-Ruthenadicarbadodecaboranes

Abstract

3,1,2-Ruthenadicarbadodecaborane complexes bearing the [C2B9H11]2− (dicarbollide) ligand are robust scaffolds, with exceptional thermal and chemical stability. Our previous work has shown that these complexes possess promising anti-tumor activities in vitro, and tend to form aggregates (or self-assemblies) in aqueous solutions. Here, we report on the synthesis and characterization of four ruthenium(II) complexes of the type [3-(η6-arene)-1,2-R2-3,1,2-RuC2B9H9], bearing either non-polar (R = Me (2–4)) or polar (R = CO2Me (7)) substituents at the cluster carbon atoms. The behavior in aqueous solution of complexes 2, 7 and the parent unsubstituted [3-(η6-p-cymene)-3,1,2-RuC2B9H11] (8) was investigated via UV-Vis spectroscopy, mass spectrometry and nanoparticle tracking analysis (NTA). All complexes showed spontaneous formation of self-assemblies (108–109 particles mL−1), at low micromolar concentration, with high polydispersity. For perspective applications in medicine, there is thus a strong need for further characterization of the spontaneous self-assembly behavior in aqueous solutions for the class of neutral metallacarboranes, with the ultimate scope of finding the optimal conditions for exploiting this self-assembling behavior for improved biological performance.

2,2′‐Bipyridine‐Modified Tamoxifen: A Versatile Vector for Molybdacarboranes

“…To understand the self‐assembling behavior of metallacarboranes/BSA noMg co‐assemblies, exemplarily ligand 6 and complex 10 were investigated in phosphate‐buffered saline (PBS)/DMSO mixtures at physiological pH (pH 7.4) by UV‐Vis, fluorescence and Rayleigh light scattering (RLS) spectroscopy, as well as Nanoparticle Tracking Analysis (NTA) …”

“…To understand the self-assembling behavior of metallacarboranes/BSA noMg co-assemblies, exemplarily ligand 6 and complex 10 were investigated in phosphate-buffered saline (PBS)/ DMSO mixtures at physiological pH (pH 7.4) by UV-Vis, fluorescence and Rayleigh light scattering (RLS) spectroscopy, as well as Nanoparticle Tracking Analysis (NTA). [9,29,35] For the fluorescence spectra, three excitation wavelengths were chosen (λ exc = 280, 295 and 320 nm) and the investigations were performed with two site markers, namely warfarin and ibuprofen, binding selectively to Sudlow's site I or Sudlow's site II, respectively. The same systems were investigated by UV-Vis spectroscopy in parallel.…”

Quinoline‐Conjugated Ruthenacarboranes: Toward Hybrid Drugs with a Dual Mode of Action

“…Following our recent investigations on the self‐assembly behavior of ruthenacarborane complexes in aqueous solutions at physiologic pH, the behavior of free acid 3 and ester 4 in aqueous solution was studied via UV‐vis spectroscopy and Nanoparticle Tracking Analysis (NTA) in phosphate‐buffered saline (PBS)/DMSO mixtures (pH 7.4). UV‐vis spectroscopy is a useful tool to follow the ester hydrolysis over time, when a UV‐(vis)‐active chromophore is present (in the case of 4 , the quinoline ring).…”

“…During our investigations on the medicinal chemistry of ruthena‐ and molybdacarboranes, we showed that these complexes spontaneously self‐assemble in aqueous solutions, forming nanoparticles . Using bovine serum albumin (BSA) as nanocarrier system allows to control the size of the nanoparticles to ca.…”

Preparing (Metalla)carboranes for Nanomedicine

“…] (denoted Ruthenacarborane) [48] and 1-(1carboxy-1,2-dicarba-closo-dodecaboranyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid methyl ester (denoted Indoborin), [49] in PBS/DMSO mixture, from NTA. Concentration for both compounds: 20 μM.…”