Development of a Genosensor for Sickle Cell Anemia Trait Determination

Sickle cell anemia (SCA) is a common recessive genetic condition in which patients produce hemoglobin S (HbS), an abnormal form of the protein, instead of hemoglobin A, the regular form. SCA is caused by the substitution of a single nitrogenous base adenine for thymine (GAG-> GTG), encoding valine instead of glutamine. 1 Deoxygenation of HbS leads to its polymerization, damaging the cell membrane and reducing the lifetime of erythrocytes dramatically – which, in turn, leads to anemia. In some regions of Africa, up to 40% of the population possess its genetic trait, being considered a public health serious problem 2 . As the disease is possibly deadly, presents very low cure chances and has limited treatment, carriers determination is a key feature to assist in reproducibility decisions. Currently, trait determination is mainly performed by liquid chromatography, electrophoresis and polymerase chain reaction (PCR) 3,4 . These techniques are not widely used due to its complexity, lack of portability, high price and specialized personal and equipment demand. In this study we have developed an electrochemical genosensor for simple, low cost and rapid SCA carriers determination. Single DNA strands corresponding to the sequence of a SCA carrier were immobilized in gold platforms using the self-assembled-monolayers technique. The determination of SCA trait is then performed by analyzing the film’s charge transfer resistance using Electrochemical Impedance Spectroscopy. The genosensor was able to distinguish between healthy and unhealthy subjects with great precision besides displaying a wide linear range (0.01 to 7.5 µmol/L, R 2 = 0.927). Furthermore, the device presented a detection limit of 7.0 nmol/L. We expect that such devices increases the number of SCA carriers determination, promoting early diagnosis and genetical counseling. References: 1              Barany, F. Genetic-Disease Detection and DNA Amplification Using Cloned Thermostable Ligase. Proceedings of the National Academy of Sciences of the United States of America 88 , 189-193, doi:10.1073/pnas.88.1.189 (1991). 2              Diallo, D. & Tchernia, G. Sickle cell disease in Africa. Current Opinion in Hematology 9 , 111-116, doi:10.1097/00062752-200203000-00005 (2002). 3              Ayatollahi, M. & Haghshenas, M. Application of the polymerase chain reaction to the diagnosis of sickle cell disease in Iran. Archive of Iranian Medicine 7 , 84-88 (2004). 4              Bender, M. A. & Seibel, G. D. Sickle Cell Disease .  (University of Washington, 2003).