Systematic selection of solvents for the fabrication of 3D combined macro- and microporous polymeric scaffolds for soft tissue engineering

In this study, we investigate the fabrication of 3D porous poly(lactic-co-glycolic acid) (PLGA) scaffolds using the thermally-induced phase separation technique. The current study focuses on the selection of alternative solvents for this process using a number of criteria, including predicted solubility. toxicity, removability and processability. Solvents were removed via either vacuum freeze-drying or leaching, depending on their physical properties. The residual solvent was tested using gas chromatography-mass spectrometry. A large range of porous, highly interconnected scaffold architectures with tunable pore size and alignment was obtained, including combined macro- and microporous structures and an entirely novel 'porous-fibre' structure. The morphological features of the most promising poly(lactic-co-glycolic acid) scaffolds were analysed via scanning electron microscopy and X-ray micro-computed tomography in both two and three dimensions. The Young's moduli of the scaffolds under conditions of temperature, pH and ionic strength similar to those found in the body were tested and were found to be highly dependent on the architectures.

Sustained swimming performance and muscle structure are altered by thermal acclimation in male mosquitofish

Males of the eastern mosquito fish (Gambusia holbrooki) possess one of the widest reproductively active temperature ranges for any ectotherm, ranging across seasons from at least 18degreesC to 34degreesC. In this study, we tested the ability of male G. holbrooki to acclimate their sustained swimming performance following long-term exposure to 18degreesC or 30degreesC. We also investigated some of the possible physiological mechanisms associated with thermal acclimation responses in swimming performance, including changes in slow muscle fibre size and abundance and the expression of myosin heavy chains (MyHC). We found that U-crit, of 18degreesC-acclimated G. holbrooki was 20% greater at 18degreesC than 30degreesC-acclimated fish, and the Ucrit of the 30degreesC-acclimated group was more than 15% greater at 30degreesC. Slow, fast and intermediate muscle fibres were identified on the basis of their myosin ATPase staining reaction. Although the number of slow and intermediate muscle fibres was similar between groups, the total cross-sectional area of aerobic fibre types was 40% greater in 18degrees-than 30degreesC-acclimated fish, reflecting an increase in the average fibre diameter. An S58 antibody raised against chicken slow skeletal muscle myosin stained a sub-set of the slow fibres identified by myosin ATPase staining. The number of S58-positive muscle fibres was 50% greater in 30degreesC-than 18degreesC-acclimated fish, implying that different MyHCs are being expressed in cold and warm acclimated individuals. Given the sexually coercive mating system of this species, increases in the sustained swimming performance via thermal acclimation may benefit the ability of males to maintain a high rate of sneaky copulations. (C) 2004 Elsevier Ltd. All rights reserved.