Summary
     Tissue engineering is an interdisciplinary science that applies the principles of engineering and life sciences to develop biological substitutes to restore, maintain or improve tissue function. The most common approach for engineering biological substitutes is based on living cells, biochemical factors and polymer scaffolds. Despite many advances, tissue engineers still face significant challenges in repairing or replacing tissue that serve predominantly biomechanical functions such as bone tissue and articular cartilage. In this sense, the tri-dimensional materials (scaffolds) play an important role and should meet the following requirements: the scaffold should possess interconnecting pores to favour tissue integration and vascularization, should be biocompatible with the tissue, biodegradable at the ideal rate corresponding to the new tissue formation, and possess optimal mechanical properties and adequate chemistry surface to favour cellular attachment, differentiation and proliferation. 
     In this context, chitosan has been found a fascinating candidate in a wide range of applications along with unique biological properties including biocompatibility, biodegradability to harmless product, non-toxicity and can be formulated in a variety of forms including powders, microparticles, scaffolds, and films. The choice of chitosan as a tissue support material is governed among others by multiple ways by which its biological, physical and chemical properties can be controlled under mild conditions. That is why; the great challenge of this work is the development of different materials based in chitosan for tissue engineering (polycaprolactone/chitosan blends, implantable chitosan scaffolds and a model of injectable scaffolds from crosslinked chitosan microparticles). 
     Blends of polycaprolactone and chitosan (prepared by casting from the mixture of solution of both components in suitable solvents) were prepared with different compositions of both components, and also we study the behaviour of different properties (water absorption capacity, surface energy, mechanical properties, cristalinity, etc.) with the content of hydrophilic component. On the other hand, we studied the cell response on the materials, concluding that the hydrophilicity in this case is not directly related with the biological response and the samples with 20wt% of chitosan shows better results than the other blends with respect to chondrocyte viability and proliferation.
The chitosan scaffolds with interconnected and spherical pore were prepared by combine the freeze-gelation and leaching out techniques. The biological response of these materials was evaluated seeding in its “Goat Bone Marrow Stromal Cell (GBMSCs)” differentiated to osteoblastic cells. Also, primary chondrocytes was seeding into the scaffolds and experiments were conducted for four times at static conditions and in an intermittent stirred flow bioreactor. In static conditions, the cells proliferated well and covered the surface of chitosan scaffolds by dense layer of cells, while the chondrocytes grown in the bioreactor has a rounded shape and tend to form cell cluster inside the pores.
     Finally, a novel injectable scaffold model from crosslinked chitosan microparticles was proposed for tissue engineering through minimally invasive surgical procedures. Genipin crosslinked chitosan microparticles were prepared by water/oil crosslinking emulsion technique. Its biological response were analysed seeding GBMSCs on chitosan particles; the obtained results shows that the cell spread on their surface joining them to form a 3D construct in which microparticles play the role of the scaffolds.