Chemiluminescently labeled aptamers as the affinity probe for interaction analysis by capillary electrophoresis

Aptamers are nucleic acid oligonucleotides, which can recognize targets with high affinity and specificity. Fluorescently labeled aptamers have been used as affinity probes in CE for interaction analysis. In this study, a method of labeling aptamers chemiluminescently with isoluminol isothiocyanate (ILITC) through covalent bonds was proposed and realized. The ILITC-labeled aptamers were characterized by HPLC-MS and purified by HPLC. After desalination, the ILITC-labeled aptamers were employed as the affinity probe for interaction analysis in CE coupled with chemiluminescence detection (CE-CL) by interface of end column reaction mode, the apparatus of which was home-designed and setup. CE-CL experiment conditions, including buffer pH, concentrations of horseradish peroxidase and H(2)O(2), were optimized first. The system of thrombin and its 29-mer aptamer was chosen as the model. Binding parameters, namely the dissociation constant (K(d)) and the binding site number (n), were calculated. The K(d) obtained was 124.0+/-6.9 nM in agreement with the reported values. Thus, interaction analysis method based on chemiluminescently labeled aptamers as the affinity probe in CE-CL has been established. This method can be widely applied due to the ease and universality of the labeling method, simplicity of CE-CL apparatus and combination with aptamers for a wide range of targets.