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A staggering number of medical devices, diagnostic and therapeutic products that are designed to improve the health of mankind have exploited biomaterials as platform technologies (Peppas et al., 2006). Defined as natural or synthetic materials (other than drugs) to treat, augment, or replace any tissues, organ, or function of living tissues, biomaterials design requires both materials and biological considerations. In addition to the mechanical requirements, biomaterials have to accomplish some specific requirements, such as non-toxicity, desired functionality, sterilizability and biocompatibility (Rosiak & Yoshii, 1999). Despite the widespread use of biomaterials in medicine, most biomaterials do not provide all of the desired requirements to interact with biological systems. Therefore, there is a significant progress to redesign current biomaterials or to develop new materials in order to overcome limitations associated with fulfilling the above-mentioned requirements. Although the term biomaterial includes metals and ceramics, polymers account for the vast majority. In this last group, hydrogels, having considerable biocompatibility and similarity with tissue components of the body, have demonstrated great potential as one of the most promising groups of biomaterials (Rosiak & Yoshii, 1999; Rogero et al., 2003).

Hydrogels are three-dimensional (3D) materials with the ability to absorb large amounts of water while maintaining their dimensional stability. The 3D integrity of hydrogels in their swollen state is maintained either by physical or chemical crosslinking. Lower interfacial tension, soft and tissue-like physical properties, higher permeability to …