IN SILICO EVALUATION OF FOLDING AND STRUCTURAL STABILITY OF APTAMERS FOR APPLICATION IN THE DESIGN OF A BIOSENSOR FOR TESTOSTERONE DETECTION

Currently, dietary supplements contain a wide range of non-specific concentrations of testosterone and/or its synthetic analogues, substances that are not permitted and that pose a risk to public health, which puts into perspective the need to evaluate and regulate the composition of these products. The present project proposes as a control tool, the development of a biosensor using aptamers as bio-recognition elements. Aptamer is specific sequence of oligonucleotides with the ability to fold into unique three-dimensional structure that interact with the analyte (testosterone and analogues). In an integral way it is proposed that the aptamers are coupled to gold nanoparticles functioning as a census and signal transduction system conducing to a biosensor with high sensitivity and selectivity, as well as rapid response. In this work, modeling and molecular docking tools were used to evaluate the folding and structural stability of the aptamers. It is essential to carry out the in silico analysis, in a complete way for the bio-recognition system, to evaluate the stability of the proposed aptamers to various variations in the medium, allows to determine the conditions and adaptations necessary for experimental, design and operation of the biosensor. On the other hand, evaluating the affinity and identifying the type of interactions between aptamer and analyte, allows to locate the best candidate, of the proposed aptamers. The stability of a set of nine sequences, with proven interaction towards testosterone, was evaluated under different conditions: folding temperature (8.0 °C, 20 °C and 30 °C), [Na+] (1.0 mm M, 50 mM and 150 mM) and [Mg²⁺] (1.0 mm M, 2.0 mM, 3.0 mM and 4.0 mM), with Mfold web server, RNA Composer and PyMOL. The affinity and molecular interaction assays were carried out between each of the aptamers and three analytes: testosterone, testosterone undecanoate and androstenedione using Autodock Vina, Chimera, Pymol and Discovery Studio. The results of stability and conformational changes of the aptamers are exposed in a graph of three variables, and it was obtained the aptamers (T6, T5.1 and TESS1) are compatible with the conditions to be run tests and have high affinity for testosterone, whose interactions are constituted mainly by Van der Waals forces, hydrophobic interaction and hydrogen bonds.