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Polymer scaffolds are obtained in which the geometric characteristics (pore size, connectivity, porosity) and the physico-chemical properties of the resulting material can be controlled in an independent way. The interconnected porous structure was obtained using a template of sintered PMMA microspheres of controlled size. Copolymerization of hydrophobic ethyl acrylate and hydrophilic hydroxyethyl methacrylate comonomers took place in the free space of the template, different comonomer ratio gave rise to different hydrophilicity degrees of the material keeping the same pore architecture. The morphology of the resulting scaffolds was investigated by scanning electron microscopy (SEM), the porosity of the material calculated, and the mechanical properties compared with those of the bulk (non porous) material of the same composition.

Two series of 3D scaffolds based on ε-caprolactone were synthesized. The pore size and architecture (spherical interconnected pores) was the same in all the scaffolds. In one of the series of scaffolds, made of pure ε-polycaprolactone, the volume fraction of pores varied between 60% and 85% with the main consequence of varying the interconnectivity between pores since the pore size was kept constant. The other scaffolds were prepared with copolymers made of a ε-caprolactone-based hydrophobous monomer and hydroxyethyl acrylate, as the hydrophilic component. Thus, the hydrophilicity and, presumably, the adhesion properties varied monotonously in the copolymer series while porosity was kept constant. A suspension of human chondrocytes in culture medium was injected in the 3D scaffolds and cultured in static conditions up to 28 days. SEM and immunofluorescence assays allowed characterizing cells and extracellular matrix inside the scaffolds after different culture times. To do that, cross sections of the scaffolds were observed by SEM and confocal microscopy. The quantity of cells inside the scaffolds decreases with a decrease of the volume fraction of pores, due to the lack of interconnectivity between the cavities. The scaffolds up to a 30% of hydrophilicity behave in a similar way than the hydrophobous; a further increase of the hydrophilicity rapidly decreases cell viability. In all the experiments production of collagen type I, type II, and aggrecan was found, and some cells were Ki-67 positive, showing that some cells are adhered to the pore walls and maintain their dedifferentiated phenotype even when cultured in three-dimensional conditions.

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Alexandra… gracias por haberme acompañado en este periodo de mi vida. Mónica, "thank you, more please". De manera muy especial quiero dar las gracias a mis padres, a Ana y al resto de mi familia por su apoyo incondicional. Este trabajo fue financiado por el Ministerio de Ciencia y Tecnología del Gobierno de España a través del proyecto MCYT MAT2001-2678-C02-01, el cual también financió mi beca FPI.