Electrochemical aptasensors for diagnostics and analysis of biological samples. Important aspects
Authors:   Tomsk State University, Shabalina A.V. 
Published: June 2021

The transition to personalized medicine requires a continuous improvement in the quality of diagnostics, and, consequently, improvement and effi ciency of the use of diagnostic tools. Biosensors have high potential in the fi eld of clinical diagnosis, especially in the early stages of diseases. Th e use of postgenomic technologies, in particular the use of DNA-aptamers, which are recognizing biomolecules, as part of biosensors, in combination with highly sensitive methods of analysis, such as electrochemical ones, can further increase the potential of using biosensor systems. Because it becomes possible to determine the presence of target objects (for example, tumor markers or markers of other diseases) with high sensitivity and selectivity of analysis. However, despite the rapid growth in the number of scientifi c research and publications in the fi eld of the development of electrochemical biosensors based on aptamers (aptasensors), at the moment the commercialization of the products obtained occurs slowly and to a low level. Th e market of biosensors is still dominated by enzymes and antibodies-based sensors that are standardized in the industry. Th is is probably due to the fact that the business originated from enzymes/antibodies utilization at fi rst. But also the general lack of knowledge on the performance of aptasensors in research and in practical use plays an important role [1]. Th e latter, inter alia, is a consequence of the lack of a proven theoretical base to date, of confi rmed key mechanisms and patterns governing the processes of obtaining the response of an electrochemical aptasensor. However, it is obvious that the confi rmed knowledge of the key patterns and mechanisms of the biosensor response formation in the presence of the target object will allow a suffi ciently high degree of control of this process to optimize the analysis procedure and increase its effi ciency and stability of the aptasensor making it suitable for the practical use. A large variety of approaches are used for new electrochemical aptasensors development. Among them there are diff erent signal amplifi cation strategies, nanoparticles and other biomolecules addition to the aptasensor’s construction, more complicated signal formation schemes, and so on [2]. So, the fi rst important aspect is the fact that every new-developed approach requires theoretical consideration and deep study of the sensing mechanism. Before developing an aptasensor for the commercial purposes, one should consider the target task and the specifi c requirements, namely sampling and samples’ preparation, analyte’s type and the targeted concentration range, the possible composition of the matrix, noise, the fi nal cost of the device, etc. [2-5]. Th us, two next important aspects are the necessity to take into account the real samples’ specifi city and the request for the minimal possible price. Th e last important point that needs to be highlighted is the analytical signal of the electrochemical aptasensor itself. Normally, for the entire electrochemical response recorded in the form of dependences of one or more parameters on the programmed eff ect (current, potential, frequency), one feature is selected (called an analytical signal), by which all the data is analyzed. More frequently, to detect the presence of the target analyte, the magnitude of the selected feature is compared for the response of the biosensor before and aft er contact with the test sample (for example, [6]). However, the responses are complex and are composed of many features. Th e signal can be either a nontrivial feature, or it might be their pair or a triple combination. Identifi cation of the informative part of the response is the work of obtaining/generating an aptasensor signal. So, in the present work, four important aspects that need to be considered during electrochemical aptasensor development were pointed out. Not all of them are widely presented in the literature, but still, they require the attention of the researchers.