Revista nº 803

11 Campos F. Hidrogeles de gelatina para ingeniería tisular Actualidad Médica · Número 803 · Enero/Abril 2018 Páginas 9 a 12 Microscopic characterization of crosslinked type A gelatin The Hematoxylin-eosin staining revealed a majority of basophil structures in all the experimental groups and different structural patterns appeared according to the crosslinking degree of the hydrogel as shown in Figure 2 . An organized structure with fibers aligned in parallel were only found in 2,5% GA crosslinked hydrogels whereas a typical porous pattern was found in the other experimental groups (5% and 8%). Nevertheless, the hydrogel crosslinked with 8% GA manifested a higher degree of porosity with a more defined porous structure along the transversal section of the sample. Apart from this, scanning electron microscopy analysis confirmed that Type A gelatin ultrastructure have a greater number of smaller and more defined pores in high glutaraldehyde concentrations compared with 2,5% GA crosslinked hydrogels. DISCUSSION Biomaterials play a key role in tissue engineering as they provide the scaffold where cells should carry out different biological processes as migration, differentiation or proliferation. In this sense, natural materials as gelatins are biologically active molecules and typically promote excellent cell adhesion and growth which are necessary for the development of artificial tissues and organs (3). Despite the numerous advantages above commented of gelatin hydrogels show a lack of mechanical properties and a crosslink step is vital to enhance them in order to obtain scaffolds reassembling the physical characteristics of native tissues (13). In this study different concentrations of GA used as a crosslinker agent have been tested to generate different final biomaterials with different properties to broaden the potential applications of gelatin hydrogels to tissue engineering According to the macroscopic evaluation, transparency is maintained in the less crosslinked hydrogel which is an essential property of cornea (14). Its highly organized collagen lamellae could provide mechanical support and biophysical properties required for transparency. Results shown in the HE staining strengthen the idea of a linear pattern in the structural evaluation. These resultsmay suggest that lowGA concentrationmay allowthe development of homogeneous, transparent and highly organized biomaterials, especially interesting for cornea regeneration. Nonetheless, 2,5% GA concentration does not crosslink enough collagen molecules to ensure thermal stability at physiological temperature. Consequently, more studies are needed in order to improve thermostability while maintaining transparency. 5% and 8% GA crosslinked gelatin hydrogels exhibited a porous pattern in both HE staining and scanning electron microscopy analyses. More defined porous were found in the 8% GA crosslinked hydrogel. Besides high GA concentration is related to a lack of malleability and its rapid crosslinking reaction (90- 120 s) makes it an unsuitable substitute. On the other hand, 5% GA crosslinked gelatin hydrogel showed a porous pattern with a more homogeneous macroscopic appearance. According to these results, the high porosity of this biomaterial could facilitate diffusion and perfusion of oxygen in bioengineered tissues. In addition, porous pattern obtained in 5% GA crosslinked gelatin hydrogels could meet the specific requirement of cardiovascular engineered tissues due to its interbranching 3D network that certainly could enhance the nutrients and oxygen diffusion, hemodynamic performance, cellular infiltration and organization (15, 16). According to recent studies hydrogels are promising biomaterials to generate controlled properties of scaffolds through crosslinking processes . A crosslink is a physical or chemical bond that connects the functional groups of a polymer chain to another one through cova – lent bonding or supramolecular interactions such as ionic bonding, hydrogen bonding, etc (17). However, new substitutes should be generated applying different crosslinker agents such as genipin, carbodiimide or citric acid (18, 19) to improve its biophysical properties, thermostability and histological characteristics that resembles native tissues in order to build up a more translational approach in Tissue Enginering. CONCLUSSION In this study gelatin potential for tissue engineering has been tested. Optimal conditions were only found in 5% GA crosslinked hydrogels. Still, interesting findings were obtained that could be helpful to design controlled-properties scaffolds regarding its crosslinked degree that would facilitate the production of more suitable tissue-like products. REFERENCES 1. Nerem RM, Sambanis A. Tissue engineering: from biology to biological substitutes. Tissue Eng. 1995;1(1):3-13. 2. O'Brien FJ. Biomaterials & scaffolds for tissue engineering. Materials Today. 2011;14(3):88-95. 3. Keane TJ, Badylak SF. Biomaterials for tissue engineering applications. 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Martinez AW, Caves JM, Ravi S, Li W, Chaikof EL. Effects of crosslinking on the mechanical properties, drug release Figure 2: Microscopic analysis of crosslinked gelatin hydrogels. HE: Hematoxylin-eosin staining 200X. SEM: scanning electron microscopy.