DNA aptamer configuration affects the sensitivity and binding kinetics of thrombin

Thrombin is serine protease involved in the coagulation cascade, which converts soluble fibrinogen into insoluble strands of fibrin - a matrix of the blood clot formation. Development of the sensitive method of the thrombin detection in nanomolar level is important for clinical practice. In this work we applied acoustic thickness shear mode method (TSM) for study the binding of human thrombin depending on DNA aptamer configuration. We compared sensitivity of detection and binding kinetics of the thrombin to the conventional DNA aptamers and aptamer dimers immobilized at the surface of quartz crystal transducer. We have shown that aptasensors based on aptamer dimers more sensitively detect thrombin. The aptamer-thrombin complexes were also more stable as revealed from equilibrium dissociation constant, K_D, that was 4 times lower for aptamer dimers in comparison with conventional aptamers. Determination of motional resistance, R_m, from acoustic impedance analysis allowed us to find important differences in physico-chemical properties of layers formed by conventional aptamers and aptamer dimers.