Multitask Imidazolium Salt Additives for Innovative Poly(l-lactide) Biomaterials: Morphology Control, Candida spp. Biofilm Inhibition, Human Mesenchymal Stem Cell Biocompatibility, and Skin Tolerance.

Candida species have great ability to colonize and form biofilms on medical devices, causing infections in human hosts. In this study, poly(l-lactide) films with different imidazolium salt (1-n-hexadecyl-3-methylimidazolium chloride (C16MImCl) and 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16MImMeS)) contents were prepared, using the solvent casting process. Poly(l-lactide)-imidazolium salt films were obtained with different surface morphologies (spherical and directional), and the presence of the imidazolium salt in the surface was confirmed. These films with different concentrations of the imidazolium salts C16MImCl and C16MImMeS presented antibiofilm activity against isolates of Candida tropicalis, Candida parapsilosis, and Candida albicans. The minor antibiofilm concentration assay enabled one to determine that an increasing imidazolium salt content promoted, in general, an increase in the inhibition percentage of biofilm formation. Scanning electron microscopy micrographs confirmed the effective prevention of biofilm formation on the imidazolium salt containing biomaterials. Lower concentrations of the imidazolium salts showed no cytotoxicity, and the poly(l-lactide)-imidazolium salt films presented good cell adhesion and proliferation percentages with human mesenchymal stem cells. Furthermore, no acute microscopic lesions were identified in the histopathological evaluation after contact between the films and pig ear skin. In combination with the good morphological, physicochemical, and mechanical properties, these poly(l-lactide)-based materials with imidazolium salt additives can be considered as promising biomaterials for use in the manufacturing of medical devices.

Ring-tension adjusted ethylene polymerization by aryliminocycloheptapyridyl nickel complexes.

The stoichiometric reactions of 5,6,7,8-tetrahydrocycloheptapyridin-9-one (cycloheptapyridin-9-one) with various anilines lead to corresponding mixtures of 9-aryliminocycloheptapyridine and the isomeric 9-arylamino-5,6,7-trihydrocycloheptapyridine derivatives; these compounds further reacted with nickel dichloride to form 9-aryliminocycloheptapyridyl nickel chlorides, respectively. The new organic compounds were analyzed by the NMR measurements, and all the organic and complex compounds were characterized by the FT-IR spectroscopy and elemental analysis. In addition, the molecular structures of representative nickel complexes and , determined by means of single-crystal X-ray diffraction, were found to be binuclear dimers with distorted square-pyramidal geometry around the nickel centers. On activation with either ethylaluminium sesquichloride (Et3Al2Cl3) or methylaluminoxane (MAO), all nickel complex pre-catalysts exhibited high activities of up to 7.80 × 10(6) g PE mol(-1) (Ni) h(-1) toward ethylene polymerization and produced highly branched polyethylenes in narrow polydispersity. The title nickel complexes showed comparable activities with 8-arylimino-5,6,7-trihydroquinolyl nickel analogues; whilst both exhibited higher activities than did the 2-iminopyridyl nickel analogues due to the enhancement of the ring-tension of cyclic-fused pyridine derivatives.

Living polymerization of ethylene and alpha-olefins using a nickel alpha-keto-beta-diimine initiator.

A nickel alpha-keto-beta-diimine initiator can be activated using treated methylaluminoxane (MAO) to generate active sites capable of the polymerization of ethylene, propene and 1-hexene under living conditions.