Advantageous sensitivity in the DNA homolog of the RNA dopamine aptamer

A competitive enzyme-linked aptamer assay for DA was performed by using two aptamers, individually; one is a 57 mer-RNA aptamer and the other is its homolog DNA aptamer. The difference between the RNA aptamer and the DNA aptamer are based on their particular nucleotides. It is known that the lack of a hydroxyl group in the 2' position of DNA is related with its chemical and biological stability. Thus, the use of the DNA homolog of the RNA aptamer could improve the affinity toward DA due to stability and finally, lower the detection limit. In this paper, we report advantageous sensitivity and specificity of its homolog DNA aptamer assay as compared to the RNA aptamer assay. Both aptamer assays were performed with 0.01 µg mL⁻¹ of each aptamer and 1.205 × 10⁻⁸ M DA-HRP conjugate using the optimized method. A dose-response curve was constructed, and the limit of detection for the DA was determined as 6.3 × 10⁻⁸ M for RNA aptamer assay, and 3.2 × 10⁻¹² M for the homolog DNA aptamer assay, respectively. These results demonstrated that the assay sensitivity was more than 10⁴ times improved with the DNA homolog of the RNA aptamer compared to its original RNA aptamer obtained through SELEX process. Also these results confirmed that the DNA homolog of the RNA aptamer can maintained the binding site and retained a function in both structure. Thus, the switching to the DNA version of RNA aptamer is possible to bind more stably and still able to bind to dopamine.