18th May 2018.

Traditionally small molecules, such as antibiotics, have been difficult targets for ELISA development. Aptamer Group has selected aptamers that bind to small molecules, previously inaccessible to other binding technologies. Utilising our state-of-the-art automation and parallel processing techniques, we can select high affinity and highly specific aptamers against small molecule targets, in solution. These aptamers can be integrated into a variety of assay platforms, including ELISA-like assays.

Figure 1: Direct Assay – The target of interest is immobilised on the assay surface and consequently detected by the specific labelled aptamer.

In this study, we demonstrate the use of our aptamers in an ELISA-like assay. These assays have generally been limited to larger molecules (proteins etc.) due to the common requirement for a ‘sandwich pair’ of antibodies. Using state-of-the-art aptamer selection approaches, we can develop ELISA-like assays without the requirement for a ‘sandwich pair’. We have adapted these principals to allow monitoring of small molecule targets without the need for a target immobilisation step (Figure 1).

During our aptamer isolation process, we include complex matrices (e.g. milk, plasma, river water etc.) to ensure that the resulting aptamers are functional in the appropriate medium. Labelling the selected aptamers with appropriate fluorophores, or conjugating signal enhancing enzymes, allows direct detection of the interaction. This approach has been applied to the detection of difficult targets (including food/environmental contaminants, therapeutics, hormones and antibiotics).

Figure 2: Aptamer-based ELISA-like assays used to monitor antibiotic residues. The isolated aptamer shows specific, concentration dependant binding to its antibiotic target in: buffer (dark blue), plasma (red), river water (green) milk (purple) and urine (light blue).

This data demonstrates that the aptamers function in an ELISA like format; fluorescently labelled aptamers were used to detect the targets in a buffer or buffered milk sample, spiked with either the target or counter-target antibiotic. This study shows clear target specific and concentration dependant binding, in both matrices.

To discuss aptamer technology with us and see how Aptamer Group can assist with your work, please contact using the form below.