2. Dextran-based materials for biomedical applications

Dextran is a bacterial polysaccharide consisting essentially of -1,6 linked glucopyranoside residues with a small percentage of -1,3 linked residues. In the first part of the chapter we discuss methodologies to chemically modify dextran. Taking into account our previous work, we focus our attention in the oxidation of dextran and in the transesterification of dextran by enzymatic means. We discuss reaction mechanisms, strategies to control the degree of oxidation and acylation, the effect of oxidation and acylation in the final molecular weight of the derivatives, and methodologies to assess the degree of oxidation and acylation. In the second part of the chapter we discuss the use of oxidized or acylated dextran in the preparation of dextran-based hydrogels. Gelation times, swelling properties, mechanical properties, degradation profiles, cytotoxicity and in vivo profiles are given. In the third part of the chapter we focus our attention in the biomedical applications of dextran-based hydrogels namely as drug delivery systems, as scaffolds for tissue engineering, and as antifungal materials. Furthermore, we discuss strategies to design hydrogels, based in the oxidized and acylated dextran, that respond Correspondence/Reprint request: Dr. Helena Gil, Chemical Engineering Department, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal. E-mail: [email protected]