Ethylene polymerization by new chromium catalysts based on carborane [SSO] ligands.

Tridentate carborane [S, S, O] ligands 2a-2b [(HOC6H2R2-4,6)(CH2)SC(B10H10)C(Ph)2P=S, R = (t)Bu (2a), R = Me (2b)] were synthesized and characterized. Reaction of CrCl3(THF)3 with the sodium salts of ligands 2a and 2b afford six-coordinated chromium complexes 3a and 3b. EXAFS spectroscopy performed on complex 3a to describe the coordination chemistry of ligand 2a around chromium center. DFT calculations were also performed on complex 3a to analyze the structure. The preliminary screening results revealed that six-coordinated chromium complexes 3a-3b displayed good catalytic activities towards ethylene polymerization in the presence of modified methylaluminoxane. The effect of polymerization parameters such as cocatalyst, reaction temperature, ethylene pressure, and reaction time on polymerization behavior were investigated in detail. The polymer obtained from this homogeneous catalytic reaction has a fibroid morphology.

Novel borate glass/chitosan composite as a delivery vehicle for teicoplanin in the treatment of chronic osteomyelitis.

Composite materials composed of borate bioactive glass and chitosan (designated BGC) were investigated in vitro and in vivo as a new delivery system for teicoplanin in the treatment of chronic osteomyelitis induced by methicillin-resistant Staphylococcus aureus (MRSA). In vitro, the release of teicoplanin from BGC pellets into phosphate-buffered saline (PBS), as well as its antibacterial activity, were determined. The compressive strength of the pellets was measured after specific immersion times, and the structure of the pellets was characterized using scanning electron microscopy and X-ray diffraction. In vivo, the tibial cavity of New Zealand White rabbits was injected with MRSA strain to induce chronic osteomyelitis, treated by debridement after 4weeks, implanted with teicoplanin-loaded BGC pellets (designated TBGC) or BGC pellets, or injected intravenously with teicoplanin. After 12weeks' implantation, the efficacy of the TBGC pellets for treating osteomyelitis was evaluated using hematological, radiological, microbiological and histological techniques. When immersed in PBS, the TBGC pellets provided a sustained release of teicoplanin, while the surface of the pellets was converted to hydroxyapatite (HA). In vivo, the best therapeutic effect was observed in animals implanted with TBGC pellets, resulting in significantly lower radiological and histological scores, a lower positive rate of MRSA culture, and an excellent bone defect repair, without local or systemic side effects. The results indicate that TBGC pellets are effective in treating chronic osteomyelitis by providing a sustained release of teicoplanin, in addition to participating in bone regeneration.