ИСТИНА

Boronic acids are capable of selectively bind 1,2- or 1,3-diol moiety which is common structural part of saccharides. The latter (in free form or in form of glycoconjugates) are involved in a wide range of biological and pathological processes, including cancer metastasis, egg fertilization, cellular communication and many others [1]. Significant progress in area of saccharide sensors has been made by means of bioaffinity-based systems like enzymes, lectins and antibodies. However, there are known limitations of biological system related to generally low stability; high cost and complexity, restricted large-scale applications. Synthetic sensors on the contrary do not suffer from given drawbacks. We demonstrate the impedimetric boronic acid substituted polyaniline-based reagentless sensor for diol-containing substances detection. In aqueous solutions the principal reaction is a reversible formation of an anionic boronate ester. Decrease of polymer conductivity estimated from electrochemical impedance spectra is assumed to be referred to as a result of ‘self-doping’ phenomenon during complexation. Polymer conductivity vs diol concentration allows one to calculate apparent stability constant K on the base of some reasonable approximations. Typical profiles of the faradaic resistance vs. diol concentration in phosphate buffer solutions with different pH were obtained for model diols – glucose and lactate. Theoretical profile of the ester stability vs pH is represented by bell-shaped curve which position is defined by Ka values of boronic acid and diol. Significant difference in pKa values of diols (3.7 for lactate and 11.9 for glucose) gives an opportunity to predict symmetry of profiles of apparent stability constant K vs. pH in neutral region [2]. The suggestion was confirmed experimentally. Deprived of mediator limitations reagentless impedimetric system represents promising approach to investigate a robust sensor in polyol-related compounds detection field. An increase of polymer conductivity as a response upon complexation with analyte (while other presented systems show decrease of conductivity as a signal [3]) contains possibility to distinguish between specific and non-specific binding. The authors acknowledge the financial support from joint Moscow State University - LG Electronics lab. References. [1] S. Jin, Y. Cheng, S. Reid, M. Li, B. Wang, Medicinal Research Reviews, 30 (2010) 171-257. [2] M.A. Martinez-Aguirre, R. Villamil-Ramos, J.A. Guerrero-Alvarez, A.K. Yatsimirsky, The Journal of Organic Chemistry, 78 (2013) 4674-4684. [3] Y. Ma, X. Yang, Journal of Electroanalytical Chemistry, 580 (2005) 348-352.