Aptamer-based label-free electrochemical biosensors for the diagnosis of sickle cell anemia

Sickle cell Anemia (SCA) is a widespread disease that causes hemolysis of blood cells, anemia, painful episodes, organ damage, and in some cases death. Early diagnosis of sickle cell anemia is significantly useful to reduce the mortality rate and manage the disease effectively. Here, we report the selection and characterization of specific aptamers against hemoglobin A (HbA) and hemoglobin S (HbS) and their integration into the electrochemical sensing platforms. The aptamers which have the highest binding affinities toward HbA and HbS are HbA17 and HbS 4 with dissociation constants of 13.5 and 57.5 nM, respectively. Thiol-modified aptamers were immobilized on screen-printed gold electrodes (Au-SPE) and used for the label-free detection of HbA and HbS using square wave voltammetry. The voltammetric aptasensors showed high selectivity and specificity toward HbA and HbS. A cross-reactivity tests were performed showing no response when the aptasensors were incubated with the nonspecific hemoglobin. This method enabled the detection of HbA and HbS in human whole blood showing good agreement with the electrophoresis method. This suggests a great promise of this platform for differentiating between healthy individuals (HbAA), patients with sickle-cell disease (HbSS) and carriers (HbAS).