Thin-Layer Molecularly Imprinted Sensors Studied by Fluorescence Microscopy

Fluorescence microscopy was used to study a molecularly imprinted thin-layer polymeric sensor for nucleotides (MIP), in which 1,2-diphenyl-6-vinyl-1H-pyrazole-[3,4-b]-quinoline (PAQ) was used as a fluorescent functional monomer and the nucleotide, cyclic 3', 5' guanosine monophosphate (cGMP) as a template. The effects of extraction of the template and its subsequent re-adsorption on the fluorescence of the films were monitored using steady-state and time-resolved fluorescence microscopy. Six-fold fluorescence quenching of the MIP upon the analyte adsorption was observed, whereas the non-imprinted polymer (NIP) fluorescence stayed essentially unaffected. The results of steady state and time-resolved fluorescence microscopy show that the intensity and lifetime distributions are strongly affected by the molecular interactions during the extraction and re-adsorption processes. Widening of the distribution is observed when cGMP is extracted from the sensor, and narrowing of the distribution when cGMP is absorbed from its aqueous solution to the MIP.