Hydrolytic degradation of poly(para-dioxanone) films prepared by casting or phase separation

Poly(para-dioxanone) (PPD) films have been prepared by casting and phase separation, varying the concentration of the polymeric solution (2.5, 5 and 10% w/v) using hexafluoro-isopropanol as solvent and ethanol as non-solvent. The hydrolytic degradation of PPD films was studied. The samples were immersed in a phosphate buffer solution (pH = 7.4) at 37 +/- 1 degreesC for 1, 2, 4 and 6 weeks. The degradation was evaluated by analyzing the variation of melting enthalpy (DeltaH(m)) and crystallinity, determined by differential scanning calorimetry (DSC), initial temperature of mass loss (T-onset) and temperature of maximum mass loss (T-peak), determined by thermogravimetric analysis (TGA), and morphological changes observed by scanning electron microscopy (SEM). (C) 2002 Elsevier Science Ltd. All rights reserved.78340541

Miscibility and hydrolytic degradation of bioreabsorbable blends of poly(p-dioxanone) and poly(L-lactic acid) prepared by fusion

Blends of two semicrystalline polymers, poly(L-lactic acid) (PLLA) and poly(p-dioxanone) (PPD), were prepared by melting the polymers in different proportions. The miscibility, thermal behavior, dynamic-mechanical properties, and morphology of these blends were studied using differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA), and scanning electron microscopy (SEM). The melting temperature of PPD, determined by DSC, did not change with increasing PLLA content, suggesting that this system was immiscible. The presence of two glass transition temperatures detected by DMA also indicated the total immiscibility of the two polymers and this phase separation was confirmed by SEM. The stability of blends immersed in tubes containing phosphate buffer (pH = 7.4) in a thermally controlled bath at (37 +/- 1)degrees C was assessed using DSC, thermogravimetric analysis (TGA), and SEM. PLLA degraded more slowly than PPD, whereas the blends had a degradation rate that was intermediate to these two polymers. This finding indicated that it was possible to control the degradation rate of the blend by changing its composition. (c) 2006 Wiley Periodicals, Inc.10131899191

Melt behaviour, crystallinity and morphology of poly(p-dioxanone)

The melt behaviour of poly(p-dioxanone) (PPD) has been studied by differential scanning calorimetry (DSC). Crystallinity and morphology were evaluated by modulated differential scanning calorimetry (MDSC) and polarizing optical microscopy. The melting curves showed two melting endotherms, a higher melting (HM) peak at a constant temperature of 105 degreesC and a lower melting (LM) peak at temperatures depending on the crystallization temperature T-c. The corresponding peak temperature increased linearly with T-c, yielding an extrapolated value for the equilibrium melting temperature, T(m)degrees, of 114 degreesC. The occurrence of HM peak is a result of recrystallization. The optical micrographs showed a spherulitic morphology, with regular concentric rings, which might be caused by a periodical twisting of the lamellae during crystallization. (C) 2001 Elsevier Science Ltd. All rights reserved

Melt behaviour, crystallinity and morphology of poly(p-dioxanone)

The melt behaviour of poly(p-dioxanone) (PPD) has been studied by differential scanning calorimetry (DSC). Crystallinity and morphology were evaluated by modulated differential scanning calorimetry (MDSC) and polarizing optical microscopy. The melting curves showed two melting endotherms, a higher melting (HM) peak at a constant temperature of 105 degreesC and a lower melting (LM) peak at temperatures depending on the crystallization temperature T-c. The corresponding peak temperature increased linearly with T-c, yielding an extrapolated value for the equilibrium melting temperature, T(m)degrees, of 114 degreesC. The occurrence of HM peak is a result of recrystallization. The optical micrographs showed a spherulitic morphology, with regular concentric rings, which might be caused by a periodical twisting of the lamellae during crystallization. (C) 2001 Elsevier Science Ltd. All rights reserved.42198303830

The use of PLDLA/PCL-T scaffold to repair osteochondral defects in vivo

The physiological repair of osteochondral lesions requires the development of a scaffold that is compatible with the structure of the damaged tissue, cartilage and bone. The aim of this study was to evaluate the biological performance of a PLDLA/PCL-T (90/10) scaffold for repairing osteochondral defects in rabbits. Polymeric scaffolds containing saccharose (75% w/v) were obtained by solvent casting and then implanted in the medial knee condyles of 12 New Zealand rabbits after osteochondral damage with a trephine metallic drill (diameter: 3.3 mm) in both medial femoral condyles. Each rabbit received the same treatment, i.e., the polymeric scaffold was implanted on the right side while no material was implanted on the left side (control). Four and 12 weeks later histological examination revealed bone neoformation in the implant group, with the presence of hyaline cartilage and mesenchymal tissue. In contrast, the control group showed bone neoformation with necrosis, exacerbated superficial fibrosis, inflammation and cracks in the neoformed tissue. These findings indicate that the PLDLA/PCL-T scaffold was biocompatible and protected the condyles by stabilizing the lesion and allowing subchondral bone tissue and hyaline cartilage formation