Myriam Roy

Turn-on Phosphorescence by Metal Coordination to a Multivalent Terpyridine Ligand: A New Paradigm for Luminescent Sensors

A hexathiobenzene molecule carrying six terpyridine (tpy) units at the periphery has been designed to couple the aggregation induced phosphorescence, displayed by the core in the solid state, to the metal binding properties of the tpy units. Upon Mg(2+) complexation in THF solution, phosphorescence of the hexathiobenzene core is turned on. Metal ion coordination yields the formation of a supramolecular polymer which hinders intramolecular rotations and motions of the core chromophore, thus favoring radiative deactivation of the luminescent excited state. Upon excitation of the [Mg(tpy)2](2+) units of the polymeric structure, sensitization of the core phosphorescence takes place with >90% efficiency. The light-harvesting polymeric antenna can be disassembled upon fluoride ion addition, thereby switching off luminescence and offering a new tool for fluoride ion sensing. This unique system can, thus, serve as cation or anion sensor.

Gold nanoparticles prepared by laser ablation in aqueous biocompatible solutions: assessment of safety and biological identity for nanomedicine applications

Due to excellent biocompatibility, chemical stability, and promising optical properties, gold nanoparticles (Au-NPs) are the focus of research and applications in nanomedicine. Au-NPs prepared by laser ablation in aqueous biocompatible solutions present an essentially novel object that is unique in avoiding any residual toxic contaminant. This paper is conceived as the next step in development of laser-ablated Au-NPs for future in vivo applications. The aim of the study was to assess the safety, uptake, and biological behavior of laser-synthesized Au-NPs prepared in water or polymer solutions in human cell lines. Our results showed that laser ablation allows the obtaining of stable and monodisperse Au-NPs in water, polyethylene glycol, and dextran solutions. The three types of Au-NPs were internalized in human cell lines, as shown by transmission electron microscopy. Biocompatibility and safety of Au-NPs were demonstrated by analyzing cell survival and cell morphology. Furthermore, incubation of the three Au-NPs in serum-containing culture medium modified their physicochemical characteristics, such as the size and the charge. The composition of the protein corona adsorbed on Au-NPs was investigated by mass spectrometry. Regarding composition of complement C3 proteins and apolipoproteins, Au-NPs prepared in dextran solution appeared as a promising drug carrier. Altogether, our results revealed the safety of laser-ablated Au-NPs in human cell lines and support their use for theranostic applications.

Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Units

A one-step synthesis of a nanographene propeller with a D3-symmetry was obtained starting from 7,8-dibromo[5]helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported.

Synthesis, Characterization, and Metal Ion Coordination of a Multichromophoric Highly Luminescent Polysulfurated Pyrene

We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the peripheral units and funnels the energy to the very highly luminescent core. The addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three-dimensional nanoscopic objects in a dual function.

Species-dependent binding of tocainide analogues to albumin: affinity chromatography and circular dichroism study

A series of novel tocainide analogues were characterized for their HSA and RSA binding, by using high-performance liquid affinity chromatography (HPLAC) and circular dichroism (CD). In this HPLAC study, HSA and RSA were covalently immobilized to the silica matrix of HPLC columns, with a procedure that maintained unaltered the binding properties of the proteins. The tocainide analogues were ranked for their affinity to HSA and RSA on the basis of their bound fractions measured by the two albumin-based columns. This technique was also applied to characterize the high affinity binding sites of these tocainide analogues to the protein. For this purpose displacement experiments were carried out by means of increasing concentrations in the mobile phase of competitors known to bind selectively to the main binding sites of HSA. The results obtained with the immobilized proteins were confirmed by investigating the same drug-protein systems in solution by circular dichroism. The comparison of the data collected with both methodologies highlighted the dramatic effect of small differences in the amino acidic sequences of the two proteins. In fact, despite their similar primary and secondary structures, a small difference in the amino acidic sequence leads to significant differences in their three-dimensional structure reflecting their different binding capacity and their stereoselectivity. Therefore, this study confirms how it is crucial to consider the significant differences among the animal models when performing pharmacokinetic studies. It is also clear that the knowledge of serum carrier binding parameters at an early stage of drug discovery represents a great advantage that may help to save time and efforts.

Green chiral HPLC study of the stability of Chiralcel OD under high temperature liquid chromatography and subcritical water conditions

We report here the study of the stability under subcritical water conditions of one of the most popular polysaccharide chiral stationary phase (CSP): Chiralcel OD. This CSP was used under high temperature and reversed phase conditions with acetonitrile and 2-propanol as modifier, respectively. The evolution of selectivity and resolution was investigated both in normal and reversed mode conditions with five racemates after packing, heating at 150 °C and separations of some racemic compounds under different high temperatures and mobile phase conditions. The results show that after using at high temperature and subcritical water conditions the selectivity was only moderately affected while the resolution fell dramatically especially in reversed mode due to the creation of a void at the head of the columns which reflects the dissolution of the silica matrix.

Delaying Anticancer Drug Delivery by Self-Assembly and Branching Effects of Minimalist Dendron-Drug Conjugates

Self-assembly of a covalently-bound lipophilic drug to a dendronic scaffold for making organic nanoparticles is reported as a proof of concept in nanovectorization. A minimalist structural approach with a small PEG-dendron conjugated to paclitaxel (PTX), incorporating safe succinic and gallic acids, is efficient to provide the expected anticancer bioactivity, but also significantly retards and targets intracellular delivery of PTX in 2D and 3D lung cancer cell cultures. A branching effect of dendrons is crucial, when compared to linear PTX conjugates. Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) studies indicate the formation of stable, low-disperse nanoparticles at 10-5  m in H2 0, which could also be responsible for the biological effects. An ultrasensitive LC-MS/MS method was used for the determination of intracellular PTX concentration over time, along with the survival rates of cancer cells. Similarly, cell survival assays were successfully correlated to a 3D cell culture with spheroids for mimicking tumors, when treated with PTX conjugates. Our work opens the way to a full evaluation program required for new chemical entities.

Benzylic-type couplings provide an important asymmetric entry to functionalized, non-racemic helicenes

Benzylic-type couplings are key reactions to make non-racemic helicenes. Their simplicity contributes to a short, efficient, and scalable asymmetric route to functionalized [7]helicenes. It widens the scope and uses of enantiopure helicenes, which are unequivocally needed for new chiroptical-electronic materials. A mechanistic proposal featuring an electrocyclization is based on experiments, X-ray crystallography and calculations.