Three label-free thrombin aptasensors based on aptamers and [Ru(bpy)₂(o-mopip)]²

Early disease diagnosis is very important for the prevention or mitigation of metastasis. Effective and efficient methods are needed to improve the diagnosis and assessment of diseases. Thrombin is a biomarker for diagnosis of some diseases, such as pulmonary metastases and diseases associated with coagulation abnormalities. Lots of methods for detecting thrombin have been reported, however, most of them were based on a single aptamer and needed modification of aptamers, and label free sensors for thrombin detection based on an aptamer pair are challenging. In this work, we present three label free sensing platforms based on [Ru(bpy)₂(o-mopip)]²⁺ (bpy = 2,2-bipyridine; o-mopip = 2-(2-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline) (OMO) and graphene oxide (GO) for thrombin detection. Thrombin detection using our three label free sensors is accomplished by specific target recognition based on aptamer pair TBA1/TBA2-thrombin, single aptamer TBA1-thrombin or TBA2-thrombin, respectively. Direct readouts of the target recognition is achieved by restoration of the fluorescence of OMO prequenched by GO. All of the three sensing platforms exhibited high sensitivity and selectivity. Furthermore, all sensing platforms were successfully applied to thrombin analysis in diluted bovine serum. According to the thrombin dependent response of the three platforms, the sensing platform based on aptamer pair TBA1 and TBA2 showed the highest sensitivity, widest linearity, best selectivity and recovery in diluted serum to thrombin. These results show that the sensing platform based on an aptamer pair have great potential for clinical diagnosis of disease-related biomarkers.