Summary.


   The development of tissue engineering was born at of the necessity to give a solution to the great number of diseases that resulted in
 tissue damage. For that reason, the focus of this thesis is tissue regeneration, which can be an alternative to organ transplants. With this goal,
 the procedure to follow will be the use of live cells to repair the damaged tissue. The method is the following: first, to eliminate the damaged
or sick tissue and, second, to introduce the necessary tissue-repairing cells in conditions that are optimal to enhance tissue regeneration. 
This method requires the use of a matrix or scaffold that guides the tissue while it is growing. For example, the chondrocyte cells are cultured
 and their growth is produced inside the scaffolds. Once the cells are developed, they are implanted into the damaged area. In order to use
 the scaffolds in tissue engineering applications, these scaffolds must follow several requirements: The material must be compatible and easily 
sterilizable; the pores of the scaffolds must be interconnected and, depending on each particular application a specicific porosity and pores 
diameter might be more favorable. The material must have appropriate mechanical characteristics and thus, some compositions are more 
suitable than others. Therefore, the main aim of this thesis is to synthesize scaffolds, with the intention to use them in tissue engineering
 applications that is, in tissue regeneration processes, or in vitro cells cultures. In conclusion, in any of these cases, the use of scaffolds in 
tissue engineering operations will contribute to fight tissue diseases and improve general health problems in our society. 
The composition used in this research belongs to the acrylate family and the main monomer used is ethyl acrylate (EA). This acrylate is a 
hydrophobic monomer that, when polymerization takes place, results in a biocompatible material. It has already been utilized in biomedicine 
applications with great success. The EA is copolymerized with hydroxyethyl methacrylate (HEMA), with the purpose of studying, on the one
 hand, the variation of hydrophilicity of the bulk polymer and to characterize the structure of these copolymers; i. c. to understand the 
distribution of hydrophilic domains. In this research, we took standard dynamic-mechanical and thermal measurement in order to perform 
experiments of structural relaxation, aiming at obtaining a deeper view of conformational movement that take place at several temperatures. 
The next step is to understand the influence of sterilization on one series of variable hydrophilicity copolymers. In this study, the different 
copolymers undergo irradiation with several doses of gamma radiation. In order to understand the influence of the gamma radiation dose
 over the physical-chemical and mechanical properties of irradiation materials. We need to find out whether the block material undergoes 
scissions and/or crosslinking, and also the possible changes in the functional groups by performing dynamic-mechanical tests and infrared
 measurement in every copolymer.  The third step consists in finding a method to synthesize scaffolds with a defined architecture: an
 interconnected structure with spherical pores independent of the EA/HEMA composition. The characterization of these 3-D materials is 
performed by scanning electron microscopy (SEM), dynamic-mechanical spectroscopy and porosity measurements. The following 
objective is to determine why the porous structure collapses in its dry state. In order to study this problem, a series of porous materials 
were synthesized with different crosslinking rates. This phenomenon can be understood with the help of the SEM micrographs, the calculation 
of the porosity and its thickness before and after drying, and the glass transition temperatures (Tg) of the bulk polymers used in the porous structures.
Finally, we carried out a study of the mechanical properties of the porous materials with a determined composition (EA with 30% of 
crosslinker). This is the optimal composition where the porous material in maintained as a totally interconnected structure.
Scaffolds must show suitable mechanical properties to allow cell growing. The mechanical properties of the porous scaffold depend on 
its material nature, its relative density or porosity and its microstructural characteristics. In order to comprehend the mechanical properties
 of the porous structures, we first carried out compression experiments of the 3-D material thus obtaining a first impression of the influence 
of the geometric parameter (pore size, porosity and interconnection throat size) over the mechanical properties. This experimental data
 results is used to find a model through finite element modeling (FEM), which predicted the linear elastic behavior of the porous materials. 
The model is based on the positioning of the pores following an ideal structure based on the crystalline Face Centered Cubic (FCC) system.
 We applied the guidelines of mechanical experimental testing of compression of porous materials to this model, in order to study the
 influence of the parameters which affect the porous architecture (pore diameter, porosity, interconnection throat size) over the lineal elastic regime. Therefore, by means of FEM and through the experimental study we gain a more detailed perspective of the influence of the geometric parameters on the Young modulus.
   In conclusion, this study illuminates the microstructure or conformation of the chains when free radical polymerization of the monomers 
EA/HEMA takes place and what is the effect of sterilization processes by gamma radiation in these copolymers. Furthermore, we developed
 a method of synthesis to obtain porous scaffolds with a determined architecture (spherical and interconnected pores), with the possibility 
of producing a broad range of compositions, porosities and pore sizes. These three variables are independent, namely, a change in the
 composition does not modify the porosity nor the pore size. Finally, a model was determined through a finite element method, 
which reproduces the mechanical behavior of the scaffolds in the elastic zone and allows us to understand the influence of the geometric
 parameters of the porous structure (pore diameter, porosity and interconnection throat size) onthe Young modulus.

    There are several potential applications for these materials. Our laboratory is performing in vitro assays of chondrocyte cells, 
and it is possible to use these scaffolds for regenerating tissue cartilage or bone. Another option is to apply these scaffolds as intervertebral
 disks and, in the future, they might be used in the regeneration of nerves. On the other hand, the finite elements model can be used to 
fabricate scaffolds that suit particular needs. For example, a tissue regeneration application needs a porous structure with the architecture
 of the model, a determinate Young modulus, a determined porosity and a specific interconnection throat size, with this model we can 
choose among a wide range of composition. The model will thus provide us with the more convenient composition for each application.
 Therefore, this developed model will allow us to obtain the parameters of optimal design for porous scaffolds without the need to synthesize 
them previously.