Polymeric Encapsulation of Novel Homoleptic Bis(dipyrrinato) Zinc(II) Complexes with Long Lifetimes for Applications as Photodynamic Therapy Photosensitisers

The use of photodynamic therapy (PDT) to treat cancer has received increasing attention over the last years. However, the clinically used photosensitisers (PSs) have some limitations that include poor aqueous solubility, hepatotoxicity, photobleaching, aggregation, and slow clearance from the body, so the design of new classes of PSs is of great interest. We present the use of bis(dipyrrinato)zinc(II) complexes with exceptionally long lifetimes as efficient PDT PSs. Based on the heavy‐atom effect, intersystem crossing of these complexes changes the excited state from singlet to a triplet state, thereby enabling singlet oxygen generation. To overcome the limitation of quenching effects in water and improve water solubility, the lead compound 3 was encapsulated in a polymer matrix. It showed impressive phototoxicity upon irradiation at 500 nm in various monolayer cancer cells as well as 3D multicellular tumour spheroids, without observed dark toxicity.     

Orbitals and the Interpretation of Photoelectron Spectroscopy and (e,2e) Ionization Experiments

Electron momentum spectroscopy, scanning tunneling microscopy, and photoelectron spectroscopy provide unique information about electronic structure, but their interpretation has been controversial. This essay discusses a framework for interpretation. Although this interpretation is not new, we believe it is important to present this framework in light of recent publications. The key point is that these experiments provide information about how the electron distribution changes upon ionization, not how electrons behave in the pre‐ionized state. Therefore, these experiments do not lead to a “selection of the correct orbitals” in chemistry and do not overturn the well‐known conclusion that both delocalized molecular orbitals and localized molecular orbitals are useful for interpreting chemical structure and dynamics. The two types of orbitals can produce identical total molecular electron densities and therefore molecular properties. Different types of orbitals are useful for different purposes.     

Convenient and easy access to 2-hydroxycyclopent-2-enones from acylcyanohydrins

A convenient access to 2-hydroxycyclopentenones was designed from acylcyanohydrins, by using titanacyclopropane complexes as nucleophilic partners and an intramolecular aldol condensation in basic conditions. The development of a one-pot procedure allows a step- and atom-economic process, and the use of Grignard reagents other than ethylmagnesium bromide provided valuable 3,4-disubstituted 2-hydroxycyclopentenones. The utility of the hydroxy group was illustrated by further functionalization of the α-position using palladium-mediated cross-coupling reactions.     

Enantio- and diastereoselective synthesis of (E)-1,5-syn-diols: application to the synthesis of the C(23)-C(40) fragment of tetrafibricin

A highly stereoselective synthesis of (E)-1,5-syn-diols 6 is described. The kinetically controlled hydroboration of allenyltrifluoroborate 8 with Soderquist borane 2 provides the (Z)-allylic trifluoroborate 9, which undergoes sequential allylboration with two different aldehydes to provide (E)-1,5-syn-diols 6 in 72-98% yields with >95% ee and >20:1 dr. Application of this method to the synthesis of the tetrafibricin C(23)-C(40) fragment 19 is described.     

One-pot microwave-assisted substitution of a glucuronan trisaccharide

Substitution of a glucuronic acid trisaccharide was easily performed in one step under microwave irradiation, affording a product resulting from simultaneous glycosylation, esterification and a butyl ether formation.     

A vibrational molecular force field of model compounds with biological interest. I. Harmonic dynamics of crystalline urea at 123 K

Normal coordinate calculations have been performed for urea and deuterated urea in the crystalline state. We have used the modified Urey–Bradley–Shimanouchi intramolecular potential energy function and a rather sophisticated intermolecular energy function to reproduce I.R. and Raman frequencies with an average error of 2 cm^–1. The general agreement between the calculation and experiment suggests that intermolecular interactions must be taken into account to determine reliable intramolecular parameters of the potential energy function, mainly the barrier to internal rotation around the C? N bond. The intermolecular energy function, which consists of the Buckingham function and an explicit harmonic function for hydrogen-bonding, then has the merit to reproduce quite well the observed frequencies of lattice vibrations.     

How Carbon Nanotube Crushing can Improve Flame Retardant Behaviour in Polymer Nanocomposites?

Nanocomposites based on an ethylene–vinyl acetate copolymer (27 wt.‐% vinyl acetate) and multiwall carbon nanotubes (MWNTs) have been prepared by melt blending and their thermal degradation and flame retardant properties have been evaluated. Special attention has been paid to the influence of the nanotube nature on the flammability properties and more particularly on the time to ignition (TTI) as measured by cone calorimetry. It has been shown that there is a strong influence of the nature of carbon nanotubes on the fire behaviour of the composites, especially previous MWNTs crushing proved to substantially delay the TTI while maintaining much reduced heat release rate (HRR). Such a remarkable behaviour might be explained by the chemical reactivity of radical species present at the surface/extremities of crushed MWNTs during the combustion process.

     

Polymer microfluidic chips for electrochemical and biochemical analyses

Our recent developments concerning the fabrication of polymer microchips and their applications for biochemical analyses are reviewed. We first describe two methods of fabrication of polymer microfluidic chips, namely UV-laser photoablation and plasma etching that are well suited for the prototyping and mass fabrication of microchannel networks with integrated microelectrodes. These microanalytical systems can be coupled with various detection means including mass spectrometry, and their applications in capillary electrophoresis are presented here. We also present how UV laser photoablation can be used for the patterning of biomolecules on polymer surfaces for generating two-dimensional arrays of microspots to carry out affinity assays. Finally, the use of the microchips for the development of fast affinity and immunological assays with electrochemical detection is presented, demonstrating the potential of these polymer microchips for medical diagnostics and drug discovery.     

Glycosyl-nucleoside fluorinated amphiphiles as components of nanostructured hydrogels

The synthesis of two novel glycosyl-nucleoside fluorinated amphiphiles (GNFs) derived from the 2H,2H,3H,3H-perfluoro-undecanoyl hydrophobic chain is described. The GNF amphiphiles, which feature either β-d-glucopyranosyl or β-d-lactopyranosyl moieties linked to a thymine base via a 1,2,3 triazole linker, were prepared using a ‘double click’ chemistry route. Surface tension measurements, gelation properties, and TEM studies show that GNFs spontaneously assemble into supramolecular structures. Similarly to their hydrocarbon analogues (GNLs), the GNFs have unique gelation properties in water. A minimum hydrogelation concentration of 0.1% (w/w), was determined in the case of the β-d-glucopyranosyl derivative. Cell viability studies indicate that fluorocarbon GNF 5 was not toxic for human cells (Huh7), whereas hydrocarbon analogue GNL is toxic above 100 μm.