Application of a Nucleic Acid Based Optical Bioprobe for Environmental and Pharmaceutical Analysis

A nucleic acid based optical bioprobe for environmental monitoring is described. The sensor employs the long wavelength intercalating fluorophore ToPro-3. Compounds which interact with the ToPro-3:nucleic acid complex are detected indirectly by measuring changes in the fluorescent signal intensity. The scheme attempts to combine the broad range detection capability of whole cell assays with the speed and simplicity of specific immunoassays and compliments both strategies. Previously, we have shown that the assay scheme is capable of detecting compounds with affinity for nucleic acids ranging from carcinogens to natural products. Here we report application of nucleic acid based sensing for detecting organic solvents and heavy metal ions. In general, the solvent sensitivity of the assay follows the polarity of the solvent, i.e. toluene> DMF> DMSO> methanol. The detection limit for toluene was 0.025% or 25 ppm. A variety of metal ions have been tested including: cadmium, cerium, chromium, iron, lead, magnesium, manganese, nickel and zinc. Of these only cerium and chromium were detected. In addition, the ability of the assay to discriminate between structurally related acridine compounds was investigated. The interaction profiles follow closely what would be expect from the chemical structure of the various dyes. The assay is also capable of detecting structural differences in a series of related compounds which indicates that the assay could be useful in for determining structure activity relationships (SAR).