16.2.2 State of the Art Experiment
16.2.2.1 Natural Polymers in Gene Delivery and Tissue Engineering
Research on natural polymers for the develop-ment of matrix-based gene delivery systems has opened the way to new and exciting possibilities to be explored within the field of regenerative medi-cine [19]. In fact, the combination of gene therapy and tissue engineering exploits the potential of genetic cell engineering to provide biochemical signals that direct cell proliferation and differenti-ation, and simultaneously, the ability of natural polymers to serve as gene carriers and tissue engi-neering scaffolds. It is true that synthetic polymers and viral carriers have been preferentially used in gene delivery applications, but natural polymers have unique and intrinsic properties that can make them more suitable candidates for this type of application. Such properties include their general biocompatibility, mucoadhesive character, and biodegradability. The biocompatibility of natural polymers, e.g., allows for cells infiltration into the matrix and transfection can occur as these cells come into contact with the imbedded DNA.
The biodegradability of the matrices obtained from natural polymers may also assist the release of gene transfer agents into the surrounding environment and thus affect nearby cells. The current research suggests therefore, that natural polymeric carriers have a different mechanism for intracellular escape and transfection than synthetic polymers. However, a very limited number of studies have focused on the development of matrices based on natural polymers for gene delivery and for cell support. An interesting example is provided by research work from Lim et al. [20] in which the authors have investigated a 3D fiber-mesh scaffold, based on chitin and algi-nate, as a way to obtain a better spatial control of plasmid localization, in opposition to other avail-able systems that are based on simple mixture to bond the matrix and the gene delivery elements. In this study, chitin and alginate fibers were formed by polyelectrolyte complexation of the water-soluble polymers, and PEIeDNA nanoparticles containing green fluorescent protein (GFP)-encoding plasmid were loaded during the fiber drawing process. These fibers were then processed into a nonwoven fiber-mesh scaffold, using a method based on the needle-punching technique. This system was then studied to analyze the tranfectability of human epithelial