Systems based on alginate hydrogel fibers for tissue engineering applications

Naturally derived hydrogels are frequently employed for biomedical applications because of their properties similar to the extracellular matrix of the natural tissues. Alginates are probably the most extensively studied and characterized hydrogels for applications in tissue engineering and regenerative medicine fields. The gelation reaction of alginate is produced when cations such Ca2+ diffuse into solution and interact with specific segments of the polymer chains. In the present work polymeric fibers were produced by wet spinning, exploiting the ionotropic gelation of alginate. The method consists in immersing the needle of a disposable syringe loaded with the alginate aqueous solution, into a calcium chloride cross-linking solution. To obtain the optimum hydrogel formulation, several aspects were considered such as concentration of both alginate and calcium chloride. Different processing parameters were considered to determine the best conditions required to achieve the most adequate response in terms of mechanical stability of the produced systems. Morphology, size and shape of the produced fibers were observed by light microscopy and the mechanical properties were evaluated by tensile tests. In vitro weight loss tests were carried out to evaluate the water content of the fibers. The release properties of the fibers were tested, using albumin as model molecule, in order to evaluate the use of the fibers for the production of bioactive scaffolds. Cell encapsulation experiments were performed to assess the viability of cells incorporated into the developed hydrogel fibers and to optimize the encapsulation conditions. Fiber meshes were prepared and cell culture tests were performed to investigate the ability of the produced systems to support cell adhesion and proliferation.