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Article

Molecularly Imprinted Chitosan−Genipin Hydrogels with Recognition Capacity toward o-Xylene

Supporting Info

Bibiana M. Espinosa-García,^† Waldo M. Argüelles-Monal,^‡ Javier Hernández,^† Leticia Félix-Valenzuela,^† Niuris Acosta,^§ and Francisco M. Goycoolea*^†

Laboratory of Biopolymers, Centro de Investigacin en Alimentacin y Desarrollo (CIAD), P.O. Box 1735, Hermosillo, Sonora 83000 Mexico, CIAD-Unidad Guaymas, Carretera al Varadero Nacional Km 6.6, Guaymas, Sonora 85400, Mexico, and Instituto de Estudios Biofuncionales, Universidad Complutense de Madrid, Paseo Juan XXIII No. 1, Madrid 28040, Spain

Biomacromolecules, 2007, 8 (11), pp 3355–3364

DOI: 10.1021/bm700458a

Publication Date (Web): October 18, 2007

†

Centro de Investigación en Alimentación y Desarrollo.

‡

CIAD-Unidad Guaymas.

Universidad Complutense de Madrid.

Author to whom correspondence should be addressed. Phone: +52-662-289-2400 (ext. 248). Fax: +52-662-280-0055. E-mail: fgoyco@cascabel. ciad.mx.

Abstract

A molecularly imprinted material was developed from hydrogels of chitosan (CS) cross-linked with genipin (GNP) using o-xylene as the template molecule. Gelling time, mechanical, and diffusion properties of CS−GNP hydrogels were initially investigated to establish optimal conditions to prepare molecularly imprinted hydrogels (MIHs). The elastic modulus was found to be directly proportional to the degree of cross-linking (R = moles of genipin/moles of glucosamine) while the diffusion of water, as monitored by magnetic resonance imaging, decreased with R. CS−GNP hydrogels of varying R were imprinted with o-xylene (MIH_o_-xylene). The adsorption capacity of o-xylene by MIH_o_-xylene was greater than the corresponding control hydrogels, particularly at R = 0.25. Freundlich isotherms yielded a better fitness than Langmuir ones and afforded n and Q_maxvalues of 2.55 and 103.3 mg/g, respectively. The imprinted hydrogel showed the highest adsorption capacity for o-xylene; however, the material was not highly selective as it also exhibited the capacity to adsorb m- and p-xylene isomers. In turn, the MIH_o-_xylene showed a low adsorption when 2-fluorotoluene was used in rebinding experiments, suggesting that molecular recognition by the binding sites is influenced by the electronic and steric properties of the analyte molecule, thus effectively confirming the imprinting effect within the MIH_o-_xylene network. This work opens the possibility to future development of materials with the capacity to adsorb o-xylene analogue molecules such as contaminants bearing chlorinated aromatic structures.