Fluorescent imprinted polymer sensors for chiral amines

Abstract

Molecularly imprinted polymer (MIP) based fluorescent sensors require suitable fluorescent moieties which respond to the binding event with significant fluorescence changes. Two novel polymerisable coumarins: 6-styrylcoumarin-4-carboxylic acid (SCC) and 6-vinylcoumarin-4-carboxylic acid (VCC) have been designed and synthesised. These functional monomers allow for the preparation of fluorescent sensors of chiral amines, an important class of pharmaceutical compounds. MIPs were prepared with SCC and VCC, using (−)-ephedrine as a template and ethylene glycol dimethacrylate as a cross-linker. In MeCN, the polymers exhibited a decrease of fluorescence in response to amines, with some selectivity for the template over its enantiomer (+)-ephedrine and other structural analogues. Interestingly the response of SCC to (−)-ephedrine in the MIP occurs in the opposite direction to the change when recognition occurs in solution. The control polymers (NIPs) exhibited a lesser response to (−)-ephedrine, and no resolving power, suggesting that imprinting has been successful and selective recognition sites exist in the MIPs. Recognition in aqueous buffers at different pHs has also been investigated.