Tailoring the preparation of fluorescent molecularly imprinted polymers (MIPs) toward the detection of chemical warfare agents

Abstract: The efficiency of the molecular imprinting technology to detect a specific target analyte rests on the success of the optimization techniques employed prior to fabrication/polymerization. In this work, the influence of the nature and amount of crosslinker as well as the template-monomer ratio on the fluorescence intensity of two fluorescent polymers, 7-hydroxy-4-methylcoumarin acrylate (HMC) and 2,6-bis- acrylamidopyridine (BAP) were investigated. Target analytes were 1,4-dinitrotoluene (DNT, precursor in the preparation of TNT) and trinitrotoluene (TNT) and ricinine, an analogue of ricin. Ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TRIM) and divinyl benzene (DV55), were used as crosslinkers. It was observed that both ricinine and TNT tend to quench the fluorescence emission of HMC monomer, which is deemed useful as a mode of signal transduction to indicate the binding of these templates with the MIP sensor. Further characterization showed that HMC-based MIP prepared using DV55 as crosslinker gave the most pronounced quenching effect. On the other hand, MIP prepared using EGDMA as cross linker, was found to fluoresce strongly, with the following order of relative intensities: EGDMA >TRIM >DV55. Meanwhile, in contrast with the observations in HMC-MIP, there was an enhancement on the fluorescent signal generated by BAP-MIP in the presence of template molecules. In addition, changing the molar ratio of EGDMA in MIP and NIP prepared from BAP functional monomer also could influence the fluorescence intensities. Results suggest that both MIP and NIP prepared using a molar ratio of 1:4:10 (DNT:BAP:EGDMA) generated the highest fluorescence intensity as compared to samples with ratio 1:4:20 and 1:4:30 (DNT:BAP:EGDMA).