In vitro Implementation of Photopolymerizable Hydrogels as a Potential Treatment of Intracranial Aneurysms

Intracranial aneurysms are increasingly being treated with endovascular therapy, namely coil embolization. Despite being minimally invasive, partial occlusion and recurrence are more frequent compared to open surgical clipping. Therefore, an alternative treatment is needed, ideally combining minimal invasiveness and long-term efficiency. Herein, we propose such an alternative treatment based on an injectable, radiopaque and photopolymerizable polyethylene glycol dimethacrylate hydrogel. The rheological measurements demonstrated a viscosity of 4.86 +/- 1.70 mPa.s, which was significantly lower than contrast agent currently used in endovascular treatment (p = 0.42), allowing the hydrogel to be injected through 430 mu m inner diameter microcatheters. Photorheology revealed fast hydrogel solidification in 8 min due to the use of a new visible photoinitiator. The addition of an iodinated contrast agent in the precursor contributed to the visibility of the precursor injection under fluoroscopy. Using a customized light-conducting microcatheter and illumination module, the hydrogel was implanted in an in vitro silicone aneurysm model. Specifically, in situ fast and controllable injection and photopolymerization of the developed hydrogel is shown to be feasible in this work. Finally, the precursor and the polymerized hydrogel exhibit no toxicity for the endothelial cells. Photopolymerizable hydrogels are expected to be promising candidates for future intracranial aneurysm treatments

Zero-valent amino-olefin cobalt complexes as catalysts for oxygen atom transfer reactions from nitrous oxide

The synthesis and characterization of several zero-valent cobalt complexes with a bis(olefin)-amino ligand is presented. Some of these complexes proved to be efficient catalysts for the selective oxidation of secondary and allylic phosphanes, as well as diphosphanes, even with a direct P-P bond. With 5 mol % catalyst loadings the oxidations proceed under mild conditions (25-70 °C, 7-22 h, 2 bar N O) and afford good to excellent yields (65-98 %). In this process, the greenhouse gas N O is catalytically converted into benign N and added-value organophosphorus compounds, some of which are difficult to obtain otherwise

(L)2C2P2: dicarbondiphosphide stabilized by N-heterocyclic carbenes or cyclic diamido carbenes

Carbon phosphides, C P , may have highly promising electronic, optical, and mechanical properties, but they are experimentally almost unexplored materials. Phosphaheteroallenes stabilized by N-heterocyclic carbenes undergo a one-electron reduction to yield compounds of the type (L) C P with diverse structures. The use of imidazolylidenes as ligands L give complexes with a central four-membered ring C P , while more electrophilic cyclic diamidocarbenes (DAC) give a compound with an acyclic π-conjugated CP-PC unit. Cyclic C P compounds are best described as non-Kekulé molecules that are stabilized by coordination to the NHC ligands NHC→(C P )←NHC. These species can be easily oxidized to give stable radical cations [(NHC) C P ] . The remarkably stable molecules with an acylic C P core are best described with electron-sharing bonds (DAC)=C=P-P=C=(DAC)