Design and evaluation of thin and flexible theophylline imprinted polymer membrane materials

The aim of this work was to produce a thin, flexible and diffusion able molecularly imprinted polymeric matrix with good template accessibility. Membranes were prepared using a non-covalent molecular imprinting approach and their physical characteristics and binding capabilities investigated. Two materials were used, a poly(tri-ethyleneglycol dimethyacrylate-co-methyl methacrylate-co-methacrylic acid) copolymer containing 14% cross-linker and a monomer (g) to porogen (ml) ratio of 1:0.5 (A), and a blend of poly(TEGMA-co-MAA) and polyurethane (B). The polyurethane was added to improve membrane flexiblity and stability. The polymers were characterized using AFM, SEM and nitrogen adsorption, whilst binding was evaluated using batch-rebinding studies. For all membranes the specific surface area was low (<10 m(2)/g). MIP (A) films were shown to bind specifically at low concentrations but specific binding was masked by non-specific interactions at elevated concentrations. Selectivity studies confirmed specificity at low concentrations. K(D) approximations confirmed a difference in the population of binding sites within NIP and MIP films. The data also indicated that at low concentrations the ligand-occupied binding site population approached homogeneity. Scanning electron microscopy images of membrane (B) revealed a complex multi-layered system, however these membranes did not demonstrate specificity for the template. The results described here demonstrate how the fundamental parameters of a non-covalent molecularly imprinted system can be successfully modified in order to generate flexible and physically tolerant molecularly imprinted thin films.