Advances in Clinical Diagnosis through Electrochemical Aptamer Sensors

Volume 5 • Issue 3 • 2013 Aptamers are oligonucleotides, such as ribonucleic acid (RNA) and single-strand deoxyribonucleic acid (ssDNA) or a peptide molecule that can bind with a specific target molecule with high affinity and specificity which is due to the formation of specific three-dimensional structures. Since the discovery of aptamers, scientists have used aptamer in the fabrication of various kind biosensors such as; electrochemical, optical, fluorimetric etc. Aptamers have been considered as a biomaterial in diagnostics and also as therapeutic tool in the development of new drugs, drug delivery systems. Other advantages of aptamers are that they can be regenerated, highly stable to external factors, and does not require animal models for production [1]. Out of various kinds of clinical detection assays generally an electrochemical methods is more fascinating because it offers high sensitivity, compatibility with novel microfabrication technologies, miniaturization, and low cost. Therefore, in recent times various electrochemical aptasensors have been fabricated using several techniques such as; electrochemical impedance spectroscopy, potentiometry, and other electrochemical techniques [28]. Kim et al. selected DNA aptamers that specifically bind to estradiol through the SELEX (Systematic Evolution of Ligands by Exponential enrichment) process from a random ssDNA [8]. In this study, the DNA aptamer was immobilized on the gold electrode and estradiol was detected using a redox mediater where the sensitivity and selectivity of the detection was drastically increased. In an another study, Zhu et al. [9] successfully developed a new highly sensitive, selective, and label free sensor for the detection of anticancer drug “daunomycin” using a cancer cell surface lipid molecule “phosphatidylserine” and aptamer co-immobilized onto the nanocomposite conducting polymer film [7]. This sensor was 190 times more sensitive than the then reported any other daunomycin detection system. The strategy described in this work has many attractive features, such as: simplicity, rapidity, no requirement for a specific label (i.e., a fluorescent or reactive moiety), low-cost and hence could be a useful method in medical diagnosis.