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ISBN: 081691012X; 978-081691012-0
Conference information: Proceedings of the 2006 AIChE Annual Meeting

Abstract: Innovation on clinical devices is essential to enhance the accuracy and efficiency on patients' diagnosis, and how their clinical treatments are monitored. Molecular imprinting technique has gained attention to generate novel biosensor and clinical diagnostic devices with high sensitivity and specificity which demonstrated affinities compared to their natural counterparts. In order to rationally design a hydrogel-based imprinted gel, a method to evaluate complex formation, imprinting synthesis and MIP-ligand rebinding was completed. The extent of the association between hydrocortisone and the functional monomer, methacrylic acid (MAA) was investigated by Nuclear Magnetic Resonance (NMR) spectroscopy. Dissociation constants for the complex formation between hydrocortisone and a functional monomer analogue, acetic acid, as a function of solvent nature were estimated by NMR titration. The stoiehiometry of the complex formation between hydrocortisone and an acetic acid on each solvent was evaluated continuous variation method. Dimethyl sulfoxide and ethanol were selected as porogens to assess solvent effect. The dissociation constants obtain for ethanol-d6 reflects a greater proximity of interaction between solution adducts compared to dimethyl sulfoxide-d6. It is consequently associated by their dielectric constant of the solvents 2:1 for dymethyl sulfoxide-d6. The collective analysis of NMR titration and Job plot method indicated that the extent of shifts displacement was proportional to their proximity to the interaction site which is not apparently associated with its stoichiometric capabilities of complex formation. To evaluate synthesis condition, in situ free radical copolymerization was monitored by ATR-FTIR spectroscopy with methacrylic acid (MAA) as the functional monomer and tetra(ethylene glycol) dimethacrylate (EGDMA) as the crosslinking agent at different solvents. The synthesis was performed in the presence and absence of the template molecule. The combined set of analysis allowed a better understanding of the recognition events giving rise to the imprinting effect during MIP synthesis and to ligand-MIP binding events. In situ polymerization results demonstrated a delay the onset autoaccelaration during imprinting process. In essence, the propagation kinetics was reduced by the decrease of monomer mobility, which suggested the functional monomer-template complexation, already confirm by the NMR spectroscopic studies. Consequently, this information was applied to the design of thin films MIP. The collapse-swelling transition could be programmed to promote binding capabilities and enhance template diffusion. To this aims, hydrocortisone imprinted polymers were synthesized in aqueous medium. To determine the suitability of hydrogel-based MIPs; swelling behavior, structural parameters (e.g. mesh size, +¥) and template permeation was investigated as function of pH and copolymer composition. The MIP characterization results demonstrated an increase on template permeation influenced by mesh size at pH equal to 5.5 at 37 °C and ionic strength of 0.1 M. A different behavior was shown for the characterization at pH equal to 6.0 at 37 °C and ionic strength of 0.1 M. A reduction on the permeability coefficient was observed for MIP with a MAA/EGDMA ratio of 17:1. It suggested the influence of MlP-ligand binding on hydrocortisone transport through the polymeric network synthesized by molecular imprinting technique. Further biding capacity studies will allow the estimation of the association constants of the polymeric receptors. Overall, this work reported the evaluation of the principal factors affecting the stabilization of functional monomertemplate complex before and during imprinting process which provides essential information for the rational design of molecularly imprinted polymers
Template and target information: hydrocortisone
Author keywords: Biosensors, hydrogels, In situ polymerization, molecular imprinting, NMR titration, rational design