Recent advances in tissue engineering and regenerative medicine have shown that combining biomaterials, cells, and bioactive molecules are important to promote the regeneration of damaged tissues or as therapeutic systems. Natural origin polymers have been used as matrices in such applications due to their biocompatibility and biodegradability. This chapter provides an up-to-date review on the most promising natural biopolymers, focused on polysaccharides and proteins, their properties and applications. Membranes, micro/ nanoparticles, scaffolds, and hydrogels as biomimetic strategies for tissue engineering and processing are described, along with the use of bioactive molecules and growth factors to improve tissue regeneration potential. Finally, current biomedical applications are also presented.

In this paper we report a new type of cross-linked porous structure based on a chitosansoy protein blend system developed by means of combining a sol-gel process with the freeze-drying technique. The final structure was investigated by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), contact angle measurements and the morphology by scanning electron microscopy (SEM). The water uptake capability and the weight loss were measured up to 14 days and their mechanical properties were assessed with compression tests. Results showed that the addition of tetraethyl orthosilicate (TEOS) to the chitosan-soy protein blend system provide specific interactions at the interface between the two polymers allowing to tailor the size and distribution as well as the degradation rate of the hybrids. Finally, TEOS incorporation induces an increase of the surface energy that influences the final physicochemical properties of the materials.

Microencapsulating pancreatic islets in immunoprotective alginate hydrogels is a promising strategy for treatment of type 1 diabetes. However, this strategy is limited by inflammation and hypoxia mediated oxidative stress, due to encapsulation and the hydrogel itself, leading to impaired insulin secretion and limited short and long term cell survival. Herein, the antioxidant effect of fucoidan, an algae derived polysaccharide, on beta cells, and its positive effects on encapsulated beta cell viability and function is presented. Fucoidan from Fucus vesiculosus (FF) exhibits a high total antioxidant capacity, and free radical scavenging activity, and is able to significantly alleviate intracellular oxidative stress in rat insolinoma beta cells (INS1E). In addition, FF significantly increases insulin secretion in a dose-and time-dependent manner. When FF is incorporated in ultrapure alginate used for microencapsulation of primary rat islets, both viability and glucose responsiveness of rat islets in these socalled Fucogel microcapsules (Fucocaps) are found to be significantly higher compared to islets encapsulated in alginate alone. Similar results are obtained with INS1E pseudoislets and neonatal pig islets. Fucocaps can provide a redox-modulatory niche and an immune barrier for islets and beta cells in the same time leading to significantly improved survival and endocrine function by mitigating oxidative stress.