Competitive affinity capillary electrophoresis assay based on a "hybrid" pre-incubation/on-capillary mixing format using an enantioselective aptamer as affinity ligand

In this paper, we describe an aptamer-based competitive affinity CE (ACE) assay involving (i) the pre-incubation of the target (D-arginine) and the specific ligand (anti-D-arginine-L-RNA aptamer) before (ii) the competition with the labeled target (dansylated D-arginine) through an on-capillary mixing strategy. The effects of some critical operating parameters such as the applied voltage and the sample-aptamer mixture plug length on the assay sensitivity were investigated. The ACE assay appeared particularly dependent on the plug length of the pre-incubated sample-aptamer solution. It was shown that this "hybrid" strategy significantly improved the assay sensitivity relative to that obtained with a "full" on-capillary mixing approach.