Jairo Ernesto Perilla

New porous polycaprolactone–silica composites for bone regeneration

Polycaprolactone porous membranes were obtained by freeze extraction of dioxane from polycaprolactone-dioxane solid solutions. Porosities as high as 90% with interconnected structures were obtained by this technique. A silica phase was synthesized inside the pores of the polymer membrane by sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica precursor and catalyzed in acidic and basic conditions. Two different morphologies of the inorganic phase were obtained depending on the type of catalyst. In acid catalyzed sol-gel reaction, a homogeneous layer of silica was deposited on the pores, and discrete microspheres were synthesized on the pore walls when a basic catalyst was used. The morphology of the inorganic phase influenced the mechanical and thermal behavior, as well as the hydrophilic character of the composites. Bioactivity of the porous materials was tested in vitro by measuring the deposition of hydroxyapatite on the surfaces of the porous composite membranes. Polycaprolactone/silica composites revealed a superior bioactivity performance compared with that of the pure polymer; evidenced by the characteristic cauliflower structures on the material surface, increase in weight and Ca/P ratio of the hydroxyapatite layer. Also, the acid catalyzed composites presented better bioactivity than the base catalyzed composites, evidencing the importance in the morphology of the silica phase.

Silica coating of the pore walls of a microporous polycaprolactone membrane to be used in bone tissue engineering

Polycaprolactone/silica microporous hybrid membranes were produced in two steps: A microporous polycaprolactone membrane with an interconnected porosity of 80% was obtained via a freeze extraction procedure, then silica was formed by a sol-gel reaction inside the micropores using tetraethyl orthosilicate, TEOS, as silica precursor. It is shown that silica forms a thin coating layer homogeneously distributed over the pore walls when sol-gel reaction is catalyzed by hydrochloric acid, while it forms submicron spherical particles when using basic catalyzer. Some physical properties and the viability and osteoblastic differentiation of bone marrow rat mesenchymal stem cells cultured on pure and hybrid membranes were studied.

Mucin aggregation from a rod-like meso-scale model

Dissipative particle dynamics, a meso–scale particle-based model, was used to study the aggregation of mucins in aqueous solutions. Concentration, strength of the mucin–water interactions, as well as the effects of size, shape, and composition of the model molecules were studied. Model proteins were represented as rod-like objects formed by coarse-grained beads. In the first model, only one type of beads formed the mucin. It was found that all the surfaces were available to form aggregates and the conformation of the aggregates was a function of the strength of the mucin–water interaction. With this model, the number of aggregates was unaffected by the initial position of the mucins in the simulation box, except for the lowest mucin concentration. In a more refined mucin model, two kinds of beads were used in the molecule in order to represent the existence of cysteine-like terminal groups in the actual molecule. With this new scheme, aggregation took place by the interaction of the terminal groups between model molecules. The kinetic analysis of the evolution of the number of aggregates with time was also studied for both mucin models.

Caracterización de los monómeros DGEBA y TMAB, y seguimiento de la reacción de entrecruzamiento por espectroscopia Raman

Resumen es: La espectroscopia Raman es una tecnica ampliamente utilizada para el analisis fisico-quimico de materiales, ya que permite el estudio composicional y est...

Preparation of biopolymer films by aqueous tape casting processing

Biopolymer films have been prepared by continuous aqueous tape casting, using dextran–water solutions. The effect of dextran concentration and solution temperature on the flow behavior was studied by steady and dynamic rheological measurements. Rheological measurements revealed that increasing dextran concentration strongly increased viscosity, while increasing temperature reduced the viscosity marginally, limiting the film processing techniques to tape casting. Elastic effects were also seen in the biopolymer rheology studies, and no changes in the fluid internal microstructure were detected in the rheological measurements. The effect of casting speeds on the biopolymer film thickness was experimentally determined and compared with a pseudoplastic fluid model. Mechanical properties of the biopolymer films presented an isotropic behavior. Adding sorbitol as an external plasticizer produced more elastic films but induced an anisotropic response on the elongation at break.