Web Release Date: October 18,
Molecularly Imprinted Chitosan-Genipin Hydrogels with Recognition Capacity toward o-Xylene
ndez,
and
Laboratory of Biopolymers, Centro de Investigación en Alimentación 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
Received April 25, 2007
Revised July 30, 2007
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 (MIHo-xylene). The adsorption capacity of o-xylene by MIHo-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 Qmaxvalues 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 MIHo-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 MIHo-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.
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