Synthesis, crystallographic characterization and homogeneous catalytic activity of novel unsymmetric porphyrins

Unsymmetric porphyrins containing both pentafluorophenyl (PFP = A) and 3,4-dimethoxyphenyl (DMP = B) substituents at the meso positions were prepared using Lindsey's methodology.

Correction: Polymers of intrinsic microporosity as high temperature templates for the formation of nanofibrous oxides

Correction for ‘Polymers of intrinsic microporosity as high temperature templates for the formation of nanofibrous oxides’ by H. Al Kutubi et al., RSC Adv., 2015, 5, 73323–73326.

Polymers of intrinsic microporosity as high temperature templates for the formation of nanofibrous oxides

Highly rigid polymers of intrinsic microporosity (PIM) offer novel high temperature template materials for the formation of nano-structured metal oxides, here for nanostructured Pr₆O₁₁.

The influence of surface modification on the cytotoxicity of PAMAM dendrimers

The influence of surface modification on the cytotoxicity of PAMAM dendrimers was examined using Caco-2 cells. Dendrimers were modified by conjugating either lauroyl chains or polyethylene glycol (PEG) 2000 onto the surface of cationic PAMAM dendrimers (G2, G3, G4). The cytotoxicity of unmodified dendrimers towards Caco-2 cells was appreciably higher for cationic (whole generation) compared with anionic (half generation) dendrimers and for both types increased with increasing size (generation) and concentration. A marked decrease in the cytotoxicity of cationic PAMAM dendrimers was noted when the surface was modified, with the addition of six lauroyl or four PEG chains being particularly effective in decreasing cytotoxicity. This decrease in cytotoxicity is thought to be due to a reduction/shielding of the positive charge on the dendrimer surface by the attached chains. The cytotoxicity of dendrimer-based delivery systems is likely to be very different from the parent dendrimer.

The synthesis and glass-forming properties of phthalocyanine-containing poly(aryl ether) dendrimers

The synthesis, structural characterisation and properties of a number of phthalocyanine-containing dendrimers are described. Peripheral substitution of phthalocyanine (Pc) with four poly(aryl ether) dendritic wedges (1st, 2nd or 3rd generation) produces materials whose properties are dominated both by the columnar self-association of the Pc core and by the glass-forming character of the dendritic substituents. Asymmetric Pcs containing a single poly(aryl ether) dendron display a columnar mesophase, the structure of which can be frozen into an anisotropic glass at room temperature. Placing the dendritic wedges at the axial sites of silicon phthalocyanine prohibits self-association and gives materials from which can be fabricated robust, isotropic solid solutions of Pc with high glass transition temperatures. A single crystal X-ray diffraction analysis of one of these compounds illustrates the ability of the axial dendrons to prevent cofacial aggregation in the solid state.

Polyamidoamine Starburst dendrimers as solubility enhancers

The solubility of the hydrophobic drug ibuprofen has been compared in an aqueous solution of polyamidoamine (PAMAM) G4 dendrimer and sodium dodecyl sulphate (SDS). The PAMAM G4 dendrimer solution significantly enhanced the solubility of ibuprofen compared to 2% SDS solution. It was found that the solubility of ibuprofen in dendrimer solution was directly proportional to dendrimer concentration and inversely proportional to temperature. The influence of dendrimer solution pH on the solubility enhancement of ibuprofen suggests that it involves an electrostatic interaction between the carboxyl group of the ibuprofen molecule and the amine groups of the dendrimer molecule.

Surface modification of the biomedical polymer poly(ethylene terephthalate)

X-ray photoelectron spectroscopy was used to characterize modified surfaces of a biomedically important polymer, poly(ethylene terephthalate). Several modification schemes were investigated and direct silanization with 3-aminopropyltriethoxysilane was found to be the optimum procedure, resulting in an aminated surface. Surface coverage of up to 100% was achieved with retention of the polymeric structural integrity. Further activation of the silanized surface was accomplished with two cross-linkers, glutaraldehyde and sebacoyl chloride. A simple biomolecule, L-cysteine, was successfully immobilized onto a surface pre-treated with 3-aminopropyltriethoxysilane and glutaraldehyde, with a coverage of 42%.

Improved biocompatibility of silicone rubber by removal of surface entrapped air nuclei

Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p less than 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p less than 0.001, ANOVA). Surface chemical analysis by x-ray photo-electron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.