Poly(trimethylene carbonate-co-L-lactide) electrospun scaffolds for use as vascular grafts

Currently, there is great clinical need for suitable synthetic grafts that can be used in vascular diseases. Synthetic grafts have been successfully used in medium and large arteries, however, their use in small diameter vessels is limited and presents a high failure rate. In this context, the aim of this study was to develop tissue engineering scaffolds, using poly(trimethylene carbonate-co-L-lactide) (PTMCLLA), for application as small diameter vascular grafts. For this, copolymers with varying trimethylene carbonate/lactide ratios - 20/80, 30/70, and 40/60 - were submitted to electrospinning and the resulting scaffolds were evaluated in terms of their physicochemical and biological properties. The scaffolds produced with PTMCLLA 20/80, 30/70, and 40/60 showed smooth fibers with an average diameter of 771±273, 606±242, and 697±232 nm, respectively. When the degradation ratio was evaluated, the three scaffold groups had a similar molecular weight (Mw) on the final day of analysis. PTMCLLA 30/70 and 40/60 scaffolds exhibited greater flexibility than the PTMCLLA 20/80. However, the PTMCLLA 40/60 scaffolds showed a large wrinkling and their biological properties were not evaluated. The PTMCLLA 30/70 scaffolds supported the adhesion and growth of mesenchymal stem cells (MSCs), endothelial progenitor cells, and smooth muscle cells (SMCs). In addition, they provided a spreading of MSCs and SMCs. Given the results, the electrospun scaffolds produced with PTMCLLA 30/70 copolymer can be considered promising candidates for future applications in vascular tissue engineering.

In vivo performance of different scaffolds for dental pulp stem cells induced for odontogenic differentiation

Abstract This study was designed to determine the in vivo performance of three different materials as scaffolds for dental pulp stem cells (DPSC) undergoing induced odontogenic differentiation. An odontogenic medium modified by the addition of recombinant human bone morphogenetic protein 2 was used in the experimental groups to induce differentiation. Mesenchymal stem cell medium was used in the control groups. DPSC were transplanted onto the backs of mice via three scaffolds: copolymer of L-lactide and DL-lactide (PLDL), copolymer of DL-lactide (PDL) and hydroxyapatite tricalcium phosphate (HA/TCP). The expression levels of dentin sialo-phosphoprotein (DSPP), dentin matrix protein-1 (DMP1), enamelysin/matrix metalloproteinase 20 (MMP20) and phosphate-regulating gene with homologies to endopeptidases on X chromosome (PHEX) were analysed using RT-PCR. The expressions in the experimental groups were compared to those in the control groups. The transcript expressions at 6 and 12 weeks were significantly different for all scaffolds (p < 0.05), except for the expression of DSPP in the PLDL group with regard to the time variable. Although there was a decrease in the expression of enamelysin/MMP20 in PLDL and HA/TCP at 12 weeks, all other expressions increased and reached their highest level at 12 weeks. The highest DSPP expression was in the PDL group (p < 0.05). The highest expression of DMP1 was detected in the HA/TCP group (p < 0.05). The highest expression of PHEX was in the PLDL group (p < 0.05). Consequently, PLDL and PDL seemed to be promising scaffold candidates for odontogenic regeneration at least as HA-TCP, when they were applied with the DPSC induced for odontogenic differentiation.

Correlating the solubility of indomethacin in 1.4-dioxane + water mixtures by means of the Jouyban-Acree model / Correlación de la solubilidad de indometacina en mezclas 1.4-dioxano + agua mediante el modelo de Jouyban-Acree

In this work the validity of the Jouyban-Acree and Yalkowsky-Roseman models is evaluated to correlate the solubility of indomethacin in 1,4-dioxane + water cosolvent mixtures. The solubility correlation is studied as a function of temperature and cosolvent composition. Both models require only the experimental solubility values in the pure solvents at all the temperatures evaluated. The solubility calculated values by using both models deviate notoriously from experimental values in several cases.

En este trabajo se evaluó la utilidad de los modelos Jouyban-Acree y Yalkowsky-Roseman en la correlación de la solubilidad de la indometacina en mezclas cosolventes 1,4-dioxano + agua. La correlación de la solubilidad se estudió en función de la temperatura y la composición cosolvente. Los dos modelos requieren únicamente los valores de solubilidad en los solventes puros a todas las temperaturas de interés. Los valores calculados se desvían significativamente de los experimentales en muchos casos.

Kinetics of the resin catalysed hydrolysis of formamide in aquo-acetone and aquo-dioxane media

The kinetics of acid resin catalyzed hydrolysis of formamide in aquo- acetone and aquo-dioxane mixtures is studied at varying composition of the organic solvent [0-80%] and at temperatures ranging from 25C to 45C. Rate constant values showed that the dipolar aprotic and non- hydrogen bond donor solvents like acetone and dioxane exert a rate enhancing effect above 45% composition of the organic cosolvent. Rate constant values in aquo-dioxane are higher than those in aquo acetone medium at all temperatures studied, dioxane being a stronger hydrogen bond acceptor than acetone. This isocomposition activation energy [E exp] and the thermodynamic activation parameters were evaluated. Both delta H* and delta S* values decreased with increasing percentage of acetone or dioxane above 45% indicating solvation changes