No abstract

With the aim to construct synthetic systems that function according to the principles of enzymes, molecular clips based on diphenylglycoluril were covalently attached to (metallo)porphyrins. Two different porphyrin clips, 1 and 2, were synthesized that differ in the length and position of the linker between the clip and the porphyrin. This resulted in a great difference in flexibility of the cavity molecules, which had remarkable consequences for their binding properties in organic solution. The physical properties of the free base and zinc porphyrin clips have been studied in detail with NMR techniques and by the host−guest binding of viologen, dihydroxybenzene, and pyridine derivatives.

A series of poly(ethylene oxide)/poly(butylene terephthalate) (PEO/PBT) segmented block copolymer films was treated with a radio-frequency carbon dioxide (CO(2)) or with argon (Ar) plasma. The effects of (preferential) etching on surface structure, topography, chemistry, and wettability were studied by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. In all cases, a granular-type nanostructure was formed after prolonged CO(2) plasma etching. Ar plasma etching generally did not lead to significant changes in surface structure. Regarding surface chemistry, CO(2) plasma treatment caused surface oxidation and oxidative degradation of the films while Ar plasma etching resulted mainly in the preferential removal of PEO blocks. The wettability of all films significantly increased after plasma treatment because of the creation of polar functional groups at the surface. Preliminary goat bone-marrow cell compatibility experiments have shown that all plasma-treated PEO/PBT films induced a greatly enhanced cell adhesion and/or growth compared to untreated biomaterials. This improvement was attributed to changes in surface chemistry during plasma etching rather than to changes in surface structure. These results show that plasma-treated PEO/PBT copolymers have a high potential as scaffolds for bone tissue regeneration.

The attachment, proliferation, morphology, and differentiation of two cell types-skeletal muscle cells and chondrocytes-were investigated on different compositions of poly(ethylene glycol) and poly(butylene terephthalate) segmented block copolymers. Four weight percentages (40, 55, 60, and 70%) and two different molecular weights (300 and 1000 Da) of poly(ethylene glycol) were tested. Varying the weight percentage and molecular weight of poly(ethylene glycol) resulted in different behaviors for skeletal muscle cells and chondrocytes. The attachment of skeletal muscle was the highest (similar to tissue culture polystyrene) when copolymers containing 55 wt % of poly(ethylene glycol) were used, regardless of the poly(ethylene glycol) molecular weight. Maximum proliferation and differentiation of skeletal muscle cells was achieved when copolymers containing 55 wt % and 300 Da molecular weight of poly(ethylene glycol) were used. In contrast, the weight percentage and molecular weight of poly(ethylene glycol) had no significant effect on chondrocyte attachment and proliferation; the attached chondrocytes retained a differentiated phenotype only when a 70 wt % of poly(ethylene glycol) was used. Cell behavior was correlated with the surface properties of the copolymer films, as indicated by contact-angle measurements. These results suggest that an optimized wt % and molecular weight of poly(ethylene glycol) will be useful depending on the specific cell type.

The preparation, characterization, and in vitro bone marrow cell culturing on porous PEOT/PBT copolymer scaffolds are described. These scaffolds are meant for use in bone tissue engineering. Previous research has shown that PEOT/PBT copolymers showed in vivo degradation, calcification, and bone bonding. Despite this, several of these copolymers do not support bone marrow cell growth in vitro. Surface modification, such as gas-plasma treatment, is needed to improve the in vitro cell attachment. Porous structures were prepared using a freeze-drying and a salt-leaching technique, the latter one resulting in highly porous interconnected structures of large pore size. Gas-plasma treatment with CO(2) generated a surface throughout the entire structure that enabled bone marrow cells to attach. The amount of DNA was determined as a measure for the amount of cells present on the scaffolds. No significant effect of pore size on the amount of DNA present was seen for scaffolds with pore sizes between 250-1000 microm. Light microscopy data showed cells in the center of the scaffolds, more cells were observed in the scaffolds of 425-500 microm and 500-710 microm pore size compared to the ones with 250-425 microm and 710-1000 microm pores.