Julio San Román del Barrio

Macroporous and nanometre scale fibrous PLA and PLA–HA composite scaffolds fabricated by a bio safe strategy

The present study deals with the design, fabrication and characterization of porous scaffolds for tissue engineering made of polylactic acid (PLA) and PLA containing hydroxyapatite (HA) nanoparticles. The main novelty relies on the fact that the fabrication of the scaffolds has been achieved avoiding totally the use of toxic chemicals. In particular, the scaffolds are obtained by combining both thermal induced phase separation (TIPS) using ethyl lactate (EL) solutions and supercritical CO2 (scCO2) drying processes. Furthermore, gelatin particles have been used as a leachable porogen and combined with the previous processes to improve the control of the pore structure features of the scaffolds. The results show that the developed technique allows for the fabrication of porous PLA scaffolds with HA concentrations up to 30 wt%. Furthermore, these scaffolds are characterized by an overall porosity as high as 98% and a double scale pore structure. In particular, the appropriate control of the TIPS process and the scCO2 drying allowed for the development of nanoscale fibrous PLA and PLA–HA structures starting from PLA/EL solutions. Concomitantly, the proper selection of the size range of gelatin particles as well as their spatial distribution in the mixture allowed imprinting an interconnected network of large pores inside the scaffolds.

Barium titanate-filled bone cements. I. Chemical, physical, and mechanical characterization

Bone cements filled with BaTiO 3 particles were prepared and characterized. The powders of the cements consisted of poly(methylmethacrylate) (PMMA) beads, benzoyl peroxide (BP), and BaTiO 3 (BT) powder (<145 µm). The liquid composition was methyl methacrylate (MMA), N-vinyl-2-pyrrolidone (VP), and N,N-dimethyl-2-aminobencyl alcohol (DMOH). The observed dough and setting times were strongly influenced by the BT and VP contents. However, neither the filler nor the VP contents significantly affected the maximum temperature during setting. VP provided the cements with certain hydrophilic character and solubility. At the early stage, the process of water uptake obeyed the Fick Second Law but at the end a deviation was observed as consequence of the partial dissolution of the absorbing matrix. BT particles effectively increased the compressive strength of the cements.

Production and characterization of supercritical CO 2 dried chitosan nanoparticles as novel carrier device

The materials produced by the supercritical CO2 drying have outstanding properties that allow the incorporation of molecules in their porous structure. In this context, dried chitosan nanoparticles including β-lactoglobulin were obtained. First, the nanoparticles in water suspension were produced by ionotropic gelation incorporating the protein with high loading efficiency. Later, solvent exchange and CO2 supercritical drying procedures were performed. The physicochemical characteristics and structural properties were determined, demonstrating a stable porous structure in the dried materials and corroborating the presence of the protein after the drying. The CO2 supercritical dried chitosan nanoparticles can be effectively resuspended in acidic aqueous medium remaining in the nanoscale with minimum effect on the loading parameters. The release of the β-lactoglobulin was highly influenced by the pH, reaching around 40% under acidic conditions in ten hours. The obtained results demonstrate the possibility to apply these chitosan materials as a controlled release material.