In vitro study of antibiotic effect on bacterial adherence to acrylic intraocular lenses

Implantation of artificial intraocular lenses into the eye during ophthalmic surgical procedures ensures an unliving surface on which bacterial pathogens may attach and form biofilms. Despite antibiotic treatment bacteria growing in biofilms might cause inflammation and serious complications. In this study the adhesive ability of 7 Staphylococcus aureus and 11 coagulase-negative Staphylococcus (CNS) strains to the surface of acrylic intraocular lenses had been examined by the ultrasonic method. In untreated cases adhesion of the S. aureus and CNS strains did not differ significantly. We could not demonstrate significant differences between the adhesive ability of the standard strains and the clinical isolates. In this study a single – 60 min long – antibiotic (ciprofloxacin and tobramycin) treatment had been applied, that correlate well with the single or intermittant antibiotic prophylaxis of patients. Ciprofloxacin administration was able to reduce significantly the number of attached cells on the surface of acrylic lenses both in the case of S. aureus and CNS strains. Dependence of the effect from concentration could also be demonstrated. Tobramycin treatment was able to inhibit significantly the attachment of S. aureus cells. Despite the debate on antibiotic prophylaxis we presented in our experiments that a single antibiotic administration can decrease the attachment of bacterial cells to the surface of acrylic intraocular lenses, and might be effective in the prevention of postoperative endophthalmitis, that is a rare but serious complication of ophthalmic surgery.     

Copper-facilitated Suzuki-Miyaura coupling for the preparation of 1,3-dioxolane-protected 5-arylthiophene-2-carboxaldehydes

5-Formyl-2-thiopheneboronic acid is a widely used building block for the synthesis of diverse structures, however, due to a significant instability its transformation to 5-arylthiophene-2-carboxaldehydes by CC couplings could be performed only in low yields. Herein, as a solution, a convenient technique is described for the preparation of 1,3-dioxolane-protected 5-arylthiophene-2-carboxaldehydes via a one-pot borylation–copper(I) chloride co-catalyzed Suzuki-Miyaura coupling reaction. The utilization of the in situ prepared 2-thiopheneboronic ester derivative is allowed by the method developed. Elimination of the crucial, acidic liberation step of boronic acid species resulted in improved yields and purities. In addition, comparison of various aryl bromides is shown to demonstrate the high tolerance of the transformation to functional groups.     

High‐Pressure Synthesis of a Nitrogen‐Rich Inclusion Compound ReN8⋅x N2 with Conjugated Polymeric Nitrogen Chains

A nitrogen‐rich compound, ReN₈?x N₂, was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser‐heated diamond anvil cell. Single‐crystal X‐ray diffraction revealed that the crystal structure, which is based on the ReN₈ framework, has rectangular‐shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN₈?x N₂ is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [?N=N?]_∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN₈?x N₂ provide strong support for the experimental results and conclusions.     

The Effect of Cyclodextrins on the Photochemical Stability of 7-Amino-4-methylcoumarin in Aqueous Solution

The effect of -, - and -cyclodextrin onthe photochemical stability of 7-amino-4-methylcoumarin (C120)was studied. Using spectroscopic techniques (UV/Vis absorption spectroscopy, fluorescence, fluorescence anisotropy and circular dichroism) combined with HPLC/MS and MS analysis it was demonstrated that addition of -cyclodextrin to the aqueoussolution of C120 markedly inhibits the photodegradation of that dye. This results from theformation of an inclusion complex between C120 and -cyclodextrin.     

Stereoselective Reduction of `Capsanthol‐3′‐ones' (=3,6′‐Dihydroxy‐β,κ‐caroten‐3′‐ones) by Complex Hydrides

The (3R,5′R,6′R)‐ and (3R,5′R,6′S)‐capsanthol‐3′‐one (=3,6′‐dihydroxy‐β,κ‐caroten‐3′‐one; 4 and 5 , resp.) were reduced by different complex metal hydrides containing organic ligands. The ratio of the thus obtained diastereoisomeric (3′S)‐capsanthols 2 and 3 or (3′R)‐capsanthols 6 and 7 , respectively, was investigated. Four complex hydrides showed remarkable stereoselectivity and produced the (3′R,6′S)‐capsanthol ( 6 ) in 80 – 100% (see Table 1). The starting materials and the products were characterized by UV/VIS, CD, ¹H‐ and ¹³C‐NMR, and mass spectra.     

Absolute Configuration of Two New 6‐Alkylated α‐Pyrones (=2H‐Pyran‐2‐ones) from Ravensara crassifolia

The stem bark CH₂Cl₂ extract of Ravensara crassifolia showed antifungal activity against the phytopathogenic fungus Cladosporium cucumerinum in a bioautographic TLC assay. Activity‐guided fractionation afforded two new α‐pyrones : (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one ( 1 ) and (6R)‐6‐[(4R,6R)‐4,6‐dihydroxy‐10‐phenyldec‐1‐enyl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 2 ). Their structures and absolute configurations were established by NMR spectroscopy, chemical methods, and CD spectroscopy. The antifungal activity against C. cucumerinum was determined for both compounds.     

Leak testing of carbon–tin nanocomposites by thermal analysis methods

Electrode materials consisted of tin nanograins encapsulated in different origin carbon buffer matrix (starch or water soluble polymer) were obtained in a simple and inexpensive process. The tin precursor was synthesized using modified reverse nanoemulsion technique (w/o) and then coated by a source of carbon. The composites precursors were pyrolysed, affording formation of C/Sn anode materials. The resulting samples were investigated by powder X-ray diffraction studies in order to verify the structure and calculate crystallites sizes. The morphology of the nanocomposites was characterized by low-temperature nitrogen adsorption method (N₂-BET). Thermal analysis measurements (EGA-TG/DTG/DTA and DSC) allowed determining optimal conditions of preparation process and estimating carbon content in the obtained anode materials. Thermogravimetric studies also proved to be highly useful in establishing the leak behaviour of C/Sn nanocomposites. The electrochemical performance of the nanopowders was examined by charge–discharge tests in R2032-type coin cell. The thermal analysis results as well as low-temperature nitrogen adsorption data indicated that the origin of carbon precursor has major impact on morphology and leak behaviour of the obtained carbon buffer matrix. The electrochemical tests showed that better tightness of carbon–tin nanocomposites resulted in higher gravimetric capacity and better cell performance.     

Change of geometry of polyacetylene upon charge transfer

Crystal orbital calculations on cis- and trans-polyacethylene chains indicate two kinds of geometry changes on charge transfer. (1) increase (decrease) of the CC bond lenght and CCC bond angles in the trans conformer taking up (losing) electrons, and $\text{(u)}\text{?}$ a tendency towards bond-length equalization on electron uptake and loss for both conformers.