Eugenio Vispe

Preparation and characterization of activated montmorillonite clay supported 11-molybdo-vanado-phosphoric acid for cyclohexene oxidation

A new heterogeneous catalyst (PVMo/bentonite), consisting of vanadium substituted polyphosphomolybdate with Keggin structure H4[PVMo11O40]·13H2O (PVMo) supported on acid activated bentonite (clay from Hammam Boughrara, Maghnia, Algeria), was prepared by witness impregnation and characterized by X-ray diffraction, BET, Fourier-transformed infrared spectroscopy, 31P NMR, UV-vis diffuse reflectance spectroscopy and thermogravimetric & differential thermal analysis (TG-DTA). X-ray diffraction indicated that PVMo was properly loaded on bentonite as a support. Heterogenization of homogenous catalysts is really interesting, as heterogeneous catalysts are recoverable. Therefore, the synthesized materials can be used as efficient heterogeneous catalysts for epoxidation of cyclohexene. The obtained results showed that a better catalytic activity can be obtained with PVMo/bentonite (81.5% of conversion), by drop addition of H2O2, for 3 hours.

Heterogeneous catalysts based on supported Rh–NHC complexes: synthesis of high molecular weight poly(silyl ether)s by catalytic hydrosilylation

The new rhodium(I) complexes [Rh(Cl)(COD)(R-NHC-(CH2)3Si(OiPr3)3)] (R = 2,6-diisopropylphenyl (2a); n-butyl (2b)) have been synthesised and fully characterised. The study of their application as ketone hydrosilylation catalysts showed a clear N-substituent effect, 2a being the most active catalyst precursor. Complex 2a has been immobilised in the mesoporous materials MCM-41 and KIT-6. The new hybrid materials have been fully characterised and used as catalyst precursors for the preparation of poly(silyl ether)s by catalytic hydrosilylation. The heterogeneous catalytic systems based on the materials 2a–MCM-41 and 2a–KIT-6 afford polymers with high average molecular weight (Mw) Mw = 2.61 × 106 g mol−1 (2a–MCM-41) and Mw = 4.43 × 105 g mol−1 (2a–KIT-6).

Laponite as carrier for controlled in vitro delivery of dexamethasone in vitreous humor models

Laponite clay is able to retain dexamethasone by simple physisorption, presumably accomplished by hydrogen bonding formation and/or complexation with sodium counterions, as shown by solid state NMR. The physisorption can be somehow modulated by changing the solvent in the adsorption process. This simple system is able to deliver dexamethasone in a controlled manner to solutions used as models for vitreous humor. The proven biocompatibility of laponite as well as its transparency in the gel state, together with the simplicity of the preparation method, makes this system suitable for future in vivo tests of ophthalmic treatment.

Vinylidene-based polymers by Rh(I)-NHC catalyzed thiol–yne click polymerization: synthesis, characterization and post-polymerization modification

Complex RhCl(IPr)(pyridine)(η2-coe) (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) efficiently catalyzes the polyhydrothiolation of aromatic diynes with aliphatic dithiols to give vinylidene-based polymers (vinylidene content of 80%) with high molecular weights (Mw up to 199 000). These polymers have been shown to be chemically modifiable through hydrogenation and chemical oxidation processes.

Antibiotic-eluting orthopedic device to prevent early implant associated infections: Efficacy, biocompatibility and biodistribution studies in an ovine model: Infection Prevention Using Drug Eluting Orthopedic Implants

Infection of orthopedic devices is a major complication in the postsurgical period generating important health issues and economic consequences. Prevention strategies could be based on local release of antibiotics from the orthopedic device itself to avoid adhesion and growth of bacteria. The purpose of this work is to demonstrate the efficiency to prevent these infections by a cefazolin-eluting, perforated stainless steel implant in an in vivo ovine model. The device was placed in the tibia of sheep, one group receiving cefazolin-loaded implants whereas the control group received empty implants. All implants were experimentally infected by direct inoculation of Staphylococcus aureus ATCC 6538. In vitro cytotoxicological studies were also performed to check the effect of antibiotic on cell viability, integrity, and cycle. Results showed that sheep receiving cefazolin-loaded devices were able to avoid implant-associated infections, with normal tissue healing process. The antibiotic release followed a local concentric pattern as demonstrated by high-performance liquid chromatography detection in tissues. The in vitro results indicate the lack of relevant cytotoxic effects for the maximum antibiotic concentration released by the device. These results demonstrate the efficiency and safety of cefazolin-eluting implants in an ovine model to prevent early postsurgical infections of orthopedic devices.

Determination of Three Corticosteroids in the Biologic Matrix of Vitreous Humor by HPLC-tandem Mass Spectrometry: Method Development and Validation

ABSTRACT Purpose: To develop a simple, specific, and rapid method to determine corticosteroid concentrations in vitreous humor. Methods: An analytical method based on high-pressure liquid chromatography-tandem mass spectrometry (HPLC-MS) with a simple extraction procedure was developed. New Zealand albino rabbits (n = 54) received a single (0.1 mL) intravitreal injection of dexamethasone (DXM, 0.1 mg), methylprednisolone (MP, 2 mg), or triamcinolone acetonide (TA, 10 mg). Eyes were enucleated and mean vitreous steroid levels were quantified at 12 h and 1, 2, 3, 7, and 14 days. Results: Corticosteroids were extracted from the vitreous with acetonitrile, and TA was extracted with ethyl acetate, yielding high protein precipitation and clean solution samples. Vitreous samples were analyzed by isocratic HPLC-MS with mobile phase comprising acetonitrile and 2 mM ammonium formate buffer in water, pH 3.5. The linear range was 50–100,000 ng/g with a lower quantification limit of 45 ng/g for DXM and MP, and 50 ng/g for TA. Vitreous levels of DXM and MP were not detectable 14 days post-administration. Vitreous levels of TA were positive and stable throughout the study in both injected and control eyes. Conclusions: The HPLC-MS analytical method is an alternative to HPLC-MS/MS methods, sensitive enough for identifying and quantifying steroids in vitreous humor at a therapeutic dosage scale.