The implantation of a biomaterial for tissue engineering requires the presence of a suitable scaffold on which the tissue repair and regeneration will take place. Polymers have been frequently used for that purpose because they show similar properties to that of the natural extracellular matrix. Scaffold properties and biocompatibility are modulated by the composition of the polymers used. In this work four polysaccharide-based hydrogels (PSH) made of dextran and pullulan were synthesized. Their in vitro properties were determined and then tested in vivo in a rat model. As pullulan concentration increased in dextran hydrogels, the glass transition temperature and the maximum modulus decreased. In vitro degradation studies for 30 days demonstrated no significant degradation of PSH except for 100% pullulan hydrogel. In vivo tissue response evaluated 30 days after PSH subcutaneous implantation in rats indicated that all PSH were surrounded by a fibrous capsule. Adding pullulan to dextran induced an increased inflammatory reaction compared to PSH-D(100% dextran) or PSH-D(75)P(25)(75% dextran). This in vitro and in vivo data can be used in the design of hydrogels appropriate for tissue engineering applications.

Hybrid materials constituted by hydrophobic and hydrophilic biocompatible macromolecules are useful for biomedical applications. In this context, a well-known acrylic monomer (methyl methacrylate) was polymerized and grafted onto the polysaccharide dextran by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. The effects of concentrations of dextran, acrylic monomer, and ceric ions on the copolymerization yields were investigated in detail. The obtained polymers were studied by solubility measurements, Fourier transform infrared spectrometry, (13)C nuclear magnetic resonance spectroscopy, and viscosimetric analysis. Interestingly, we found conditions to form transparent and homogeneous thin films or 3D structures with hybrid properties. Indeed, the copolymer, but not dextran or PMMA, could be dissolved in water/THF (20/80 v/v). The thermomechanical properties of the resulting copolymer analyzed by differential scanning calorimetry and dynamic mechanical analysis showed the occurrence of a single glass-transition temperature and a marked difference with the two homopolymers. The cytocompatibility of the copolymer with human endothelial cells was evidenced by the normal cell adhesion, proliferation, and morphology after 5 days in culture on these gels. In conclusion, this type of copolymer with hybrid properties of two biocompatible macromolecules could be of great interest as a 3D scaffold or for coating in biomedical applications.

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