Molecularly imprinted polymer nanospheres as synthetic affinity receptors obtained by miniemulsion polymerisation

Highly crosslinked polymer nanospheres composed of poly[(methacrylic acid)-co-(ethylene glycol dimethacrylate)] and poly(EGDMA) have been synthesised by miniemulsion polymerisation in presence of a chiral molecular template, L- or D-Boc-phenylalanine anilid. The miniemulsions and the resulting microgels were characterised by surface tension measurements, gravimetric analysis, dynamic light scattering, transmission electron microscopy, 1H and 13C CP-MAS NMR, and Brunauer-Emmett-Teller gas adsorption measurements. The efficiency of the non-covalent molecular imprinting was examined by binding experiments and quantified by UV absorption. The miniemulsions were converted to coagulate-free and stable latexes with a conversion of 98 ± 2% and an apparent hydrodynamic particle diameter of 200 ± 20 nm. Molecular imprinting was most effective when a miniemulsion of molar ratio nMAA/nEGDMA = 0.25:1 was used for the microgel preparation. Enantioselective binding of the templates to the particles was observed. Binding of the L-enantiomer was four times greater in the L-imprinted polymer than in the non-imprinted polymer and 10 times than binding of the D-enantiomer in the L-imprinted microgels. This new method allows for a one-stage preparation of fully synthetic affinity receptors with a defined spherical shape and a high specific surface area due to their nanoscopic dimension.