Engineered biopolymers usually refer to those that, after modification by anchoring cell-specific ligands or extracellular signaling molecules to the polymer chain, are able to stimulate specific cellular response as well as to directly intervene in cell growth, differentiation, adhesion and extracellular matrix production . Implication of oligosaccharides in recognition processes and in cell signaling mechanisms addresses them as key molecules in developing materials having specific bioactivity . Along these lines, a low charge, highly hydrophilic chitosan derivative (Chitlac) was obtained by reductive amination with the lactose aldehydic group. This synthetic glycopolymer was shown to induce pig chondrocyte aggregation, leading to the formation of nodules of high dimensions (0.5-1.0 mm) as well as to stimulate type II collagen and glycosaminoglycan biosynthesis . Furthemore, the increase of expression level of galectin-1 gene and the secretion of Galectin-1 in culture medium suggested the role of Galectin-1 as bridging agent between Chitlac and chondrocyte aggregates . Galectin-1 is a member of the S-type galactoside-binding animal lectins  which binds with high affinity to polylactosamine-containing ligands (such as laminin) promoting cell adhesion to glycoconjugates [8,9]. Surphace Plasmon Resonance experiments performed on biotinylated samples proved that Galectin-1 binds to Chitlac with a high affinity that, apparently, is rather unaffected by the polymer chain length. The affinity constants obtained from both kinetic and equilibrium data for Chitlac with a chain 360 nm long did not differ much from those obtained for a Chitlac of 100 nm chain length. In contrast, Galectin-1 binds to Chitlac with an affinity that is one order of magnitude greater than that observed for free lactose in solution and about twice that reported for the binding of Galectin-3 to laminin, its natural substrate. Growing isolated chondrocytes on polymeric scaffolds suitable for implantation is a primary approach in tissue engineering involving the regeneration of tissue . The specific Galectin-1/Chitlac interaction that is at least a co-factor of the beneficial effects exerted by Chitlac in pig chondrocyte cultures and that occurs at nanoscale level, remained unaltered once the water soluble Chitlac was transformed by chemical cross-linking into a 3-D matrix. Chondrocyte-seeded scaffolds were cultured for a period of 6 weeks. At defined time intervals the cell proliferation was assessed with the AlamarBlue™ method whereas the matrix synthesis and cell morphology was investigated by SEM. Alamar Blue™ assay for cell proliferation clearly showed that the cell number increased in the first three weeks of cultures and then remained stable for the following three weeks. SEM analysis suggested the maintenance of specific bioactivity in terms of cell aggregation and extracellular matrix synthesis also after the Chitlac crosslinking procedure.  Minoo JM, Matsuda T. Molecular design of three-dimensional artificial extracellular matrix: photosensitive polymers containing cell adhesive peptide. J Polym Sci Polym Chem 1993;31:1589–97.  Hubbell JA. Bioactive biomaterials. Curr Opin Biotechnol 1999;10:123–9.  Donati I, Stredanska S, Silvestrini G, Vetere A, Marcon P, Marsich E, Mozetic P, Gamini A, Paoletti S, Vittur F. The aggregation of pig articular chondrocyte and synthesis of extracellular matrix by a lactose-modified chitosan. Biomaterials 2005;26:987–98. [6 ] Patrizia Marcon, Eleonora Marsich, Amedeo Vetere,_, Pamela Mozetic, Cristiana Campa, Ivan Donati, Franco Vittur, Amelia Gamini, Sergio Paoletti The role of Galectin-1 in the interaction between chondrocytes and a lactose-modified chitosan  Barondes SH, Castronovo V, Cooper DNW, Cummings RD, Drickamer K, Feizi T, Gitt MA, Hirabayashi J, Hughes C, Kasai K, Leffler H, Liu FT, Lotan R, Mercurio AM, Monsigny M, Pillai S, Poirer F, Raz A, Rigby PWJ, Rini JM, Wang JL. Galectins: a family of animal b-galactoside-binding lectins. Cell 1994;76:597–8.  Van den Bruˆ le FA, Buicu C, Baldet M, Sobel ME, Cooper DNW, Marschal P, Castronovo V. Galectin-1 modulates human melanoma cell adhesion to laminin. Biochem Biophys Res Commun 1995;208:760–7.  Moiseeva EP, Spring EL, Baron JH, de Bono DP. Galectin-1 modulates attachment, spreading and migration of cultured vascular smooth muscle cells via interactions with cellular receptors and components of extracellular matrix. J Vasc Res 1999;36:47–58.  Peter SJ, Miller MJ, Yasko AW, Yaszemski MJ, Mikos AG. Polymer concepts in tissue engineering. J BiomedMater Res 1998;43:422–7.
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