Abstract: Design of Aromatic Aldehyde Chitosan Derivatives for biological and Industrial Applications S. Jatunov, A. Franconetti, M. Gómez-Guillén, and F. Cabrera-Escribano^* Departamento de Química Orgánica Facultad de Química, Universidad de Sevilla Apartado de Correos No. 1203, 41071 Sevilla, Spain. Fax: +34954624960; Tel: +34954556868. e-mail: fcabrera@us.es The chemical modification of polymers confers them new interesting properties.[1] Attaching fluorescent probes to a biopolymer for instance allows the use of the polymeric material as a biosensor or for half-life determination purposes of the material in which the fluorescent probe is incorporated. Furthermore, conferring hydrophobic properties to a dilute acid soluble polymer renders it insoluble in water and might give better structural qualities for industrial purposes.[2] Our research focuses on the modification of chitosan, a natural-based polymer obtained by alkaline deacetylation of chitin, which is nontoxic, biocompatible, and biodegradable. Numerous papers have been published on chitosan revealing multiple applications for this biopolymer.[3] Therefore, chemical modification can further expand or improve its utility. We attempted the synthesis of N-substituted chitosan derivatives 2-8 from diversely functionalized aromatic aldehydes, some of them showing fluorescence, others being hydrophobic molecules and others antimicrobial. The synthesis has been carried out by reductive amination of chitosan with substituted aromatic aldehydes and sodium cyanoborohydride as reducing agent. We have also modified the primary hydroxyl group of chitosan derivatives moiety into a carboxymethyl group for some biological applications in which water solubility is required. We have also studied the non-covalent and covalent interactions between the derivatives and chitosan through the IR, NMR, and HPLC/SEC techniques. Substitution degree of each derivative was quantified with liquid and/or solid NMR. We thank the AECID (Projects A/023577/09 and A/030422/10, and fellowship to one of us, S. J.) and the Junta de Andalucía (FQM 142 and Project P09-AGR-4597) for financial support. [1] A. Mahapatro (Ed.), Polymers for Biomedical Applications 2nd ed.; American Chemical Society, 2008. [2] Y. Gnanou, M. Fontanille, Organic and Physical Chemistry of Polymers, Wiley-Interscience, 2008. [3] Se-Kwon Kim (Ed.), Chitin, Chitosan, Oligosaccharides and Their Derivatives. Biological Activities and Applications, CRC Press Taylor & Francis Group, 2011.