A fluorescence-displacement assay using molecularly imprinted polymers for the visual, rapid, and sensitive detection of the algal metabolites, geosmin and 2-methylisoborneol.

A visual, rapid, and sensitive method for the detection of two algal metabolites, geosmin (GSM) and 2-methylisoborneol (2-MIB) using a competitive displacement technique based on molecular imprinted polymers (MIPs) and fluorescent tags was developed. In this method, fluorescent tags that bind to synthetic receptor sites of MIPs were designed and synthesised. In the presence of target analytes (geosmin and 2-methylisoborneol respectively), the tags are displaced leading to fluorescence signals. The MIPs were derived from the polymerisation of functional monomers and crosslinkers in the presence of suitable templates. Good to high binding capacities and selectivities were obtained with the MIPs. The displacement of fluorescent-tagged substrates from the respective MIPs by the target analytes enabled the quantitative detection of geosmin at concentrations as low as 0.38 μM (69 μg L-1), while the LOD for 2-methylisoborneol is 0.29 μM (48 μg L-1) without any cross-reactivity, non-specific (false-positive) binding, and matrix complications. Qualitative detection of geosmin and 2-methylisoborneol is also possible via visualisation of fluorescence using a hand held UV lamp, with LOD for geosmin and 2-methylisoborneol at 0.44 μM (80 μg L-1) and 0.35 μM (60 μg L-1), respectively. The sensitivity of the system can be improved with a pre-concentration step using the respective MIPs as a sorbent.