Abstract

The main purpose of this thesis is the design of a polymeric bilayer scaffold with porous architecture for osteochondral regeneration. The material used for the construct fabrication was poly(L-lactic acid), a biodegradable polymer of the family of polyesters. One of the layers of the scaffold was designed to attend the regeneration of articular cartilage. The other layer serves as anchorage to subcondral bone, one difference with the previous layer is in the mechanical properties and the bioactivity. This behavior was obtained by combination of poly(L-lactic acid) with inorganic nanoparticles. Both layers are joined to each other by a thin layer of nonporous material, that avoids the flow of cells from one part to the other one.
For this aim, first, scaffolds with different porous morphology were fabricated varying parameters of fabrication such as the polymer concentration and the polymer / porogen ratio, in order to obtain the more suitable structure for the regeneration of both tissues. Then they were evaluated in regard to their mechanical and physical-chemical properties, in order to select the parameters of fabrication which lead to greater results. 
In tissue regeneration it is essential to know how the implant properties will vary with time when implanted and when its degradation starts. Consequently we considered opportune studying in vitro degradation of the material in different conditions. The degradation study was realised by static degradation during 6, 12, 18, 24 weeks and 1 year and fatigue essay during 1, 2, 4 and 6 weeks. Then the mechanical properties and physical-chemical properties were evaluated after the different times of degradation.
Later, and to increase the mehanical properties and bioactivity of the bone construct, different contents of bioactive nanoparticles of hydroxyapatite and silica were incorporated to the material. The influence of the incorporation of nanoparticles on the mechanical and physical-chemical properties was evaluated. Special emphasis was made in evaluating the increase of the bioactive potential provided by the inorganic filler. The bioactivity was evaluated thanks to the in vitro test consisting in studying the capacity of the material in nucleating biomimetcic hydroxyapatite crystals on its surface, while immersed in simulated body fluid during different times. 
These studies allowed selecting the optimal parameters of synthesis for the bilayer osteochondral construct, which was fabricated for in vivo evaluation in animals.