76 research outputs found
Determination of diffusion coefficients of glycerol and glucose from starch based thermoplastic compounds on simulated physiological solution
Blends of corn starch with poly(ethylene-vinylalcohol) copolymer (SEVA-C) have been
studied and reported as biodegradable. These materials are known to be sensitive to
enzymatic action, evidencing a degradation of the starch phase in α-amylase assays.
However, from the physical-chemical point of view the degradation of the blend is mainly
associated with the leaching of glycerol, since other compounds are not released and no
carbohydrates were found in the degradation solution. Based on these results, the present
work attempts to determinate the respective diffusion coefficients. Four different
experiments were performed, using samples with different thicknesses that were
immersed in a simulated physiological solution. High performance liquid chromatography
(HPLC) was used to separate the sugar derivatives and glycerol from the degradation
solutions. The obtained data were fitted to an empirical model to allow the estimation of
the diffusion coefficient for glycerol and glucose, based on the analytical solution for Fick’s
law of diffusion, and a good agreement was found (R² ≈ 1). The glycerol leaches quickly
out during the first few days of immersion, stabilizing thereafter, presenting greater
diffusion coefficients for thicker samples. As the quantity of saccharides in the solution
remains almost invariable along the experiments, this work also confirms that the
degradation process is difficult without the action of enzymes
Degradation versus self-assembly of block copolymer micelles
The stability of micelles self-assembled from block copolymers can be altered
by the degradation of the blocks. Slow degradation shifts the equilibrium size
distribution of block copolymer micelles and change their properties.
Quasi-equilibrium scaling theory shows that the degradation of hydrophobic
blocks in the core of micelles destabilize the micelles reducing their size,
while the degradation of hydrophilic blocks forming coronas of micelles favors
larger micelles and may, at certain conditions, induce the formation of
micelles from individual chains.Comment: Published in Langmuir http://pubs.acs.org/doi/pdf/10.1021/la204625
Agro-materials : a bibliographic review
Facing the problems of plastic recycling and fossil resources exhaustion, the use of biomass to conceive new materials appears like a reasonable solution. Two axes of research are nowadays developed : on the one hand the synthesis of biodegradable plastics, whichever the methods may be, on the other hand the utilization of raw biopolymers, which is the object of this paper. From this perspective, the “plastic” properties of natural polymers, the caracteristics of the different classes of polymers, the use of charge in vegetable matrix and the possible means of improving the durability of these agro-materials are reviewed
Toward osteogenic differentiation of marrow stromal cells and in vitro production of mineralized extracellular matrix onto natural scaffolds
Uncorrected proofTissue engineering has emerged as a new interdisciplinary field for the repair of various tissues, restoring their functions by using scaffolds, cells, and/or bioactive factors. A temporary scaffold acts as an extracellular matrix analog to culture cells and guide the development of new tissue. In this chapter, we discuss the preparation of naturally derived scaffolds of polysaccharide origin, the osteogenic differentiation of mesenchymal stem cells cultured on biomimetic calcium phosphate coatings, and the delivery of biomolecules associated with extracellular matrix mineralization
- …