ИСТИНА

Existing bacteria and mold sensors involve preconcentration step in order to improve detection limits. Preconcentration techniques are usually divided in three groups which use: (i) surface charging (e.g.use of polylysine or chitosan); (ii) biorecognition elements including antibodies, aptamers, lectins etc.; (iii) biomimetics of biorecognition elements. The latter one provides a powerful combination of good operational stability of charged surface and higher selectivity resembling that of biorecognition elements. Express and reliable methods of microbe detection are aimed at intact cells or colonies in order to reduce pretreatment time, complexity and cost. Since microorganisms’ cell wall consists mainly of saccharides and hydroxyacids, sensing principles utilizing affinity to these molecules are of particular interest. Boronic acid is capable selectively binding to 1,2- or 1,3-diol moiety which is common structural part of saccharides and hydroxyacids. That is why phenylboronic acid residues were already found to be useful for cell capture-release and even for bacteria detection. Impedimetric sensors are apparently among the most sensitive ones. However, these sensors, like phenylboronic acid based ones, and majority of other affinity sensors are practically useless. The reason is that commonly the signaling event consists in increase of resistance similarly to non-specific interactions. Recently our group reported on the conducting polymer based transducer with the specific signal resulting in conductivity increase [1]. The mechanism is self-doping of boronate-substituted polyaniline by freezing negative charges of boronate ring substituents as a result of binding to polyols. Since both unspecific signals and polymer degradation are resulted in resistance increase (opposite direction), the reported sensor is of practical importance allowing the discrimination of specific affinity interactions from nonspecific binding. Here we demonstrate impedimetric detection of P.chrysogenum based on conductivity increase of boronate-substituted polyaniline. For this aim we have chosen interdigitated microelectrode arrays (IDMEAs), already found to be among the most sensitive electrode structures used for this aim. Prior to detection IDMEAs were modified with poly(3-aminophenylboronic acid) in potentiodynamic regime. Impedance spectra were recorded in pure neutral aqueous buffer and after injection of mold in certain concentration. Impedance spectra in Nyquist plots (above) demonstrate decrease of film resistance (discovered from the diameter of high-frequency semicircle, starting from the bottom left part) as a function of mold concentration. As seen, polyaniline film conductivity is increased as the mold concentration is increased. It confirms the universal character of the proposed detection principle allowing discriminating specific binding over non-specific interactions. [1] E.A. Andreyev, M.A. Komkova, V.N. Nikitina, N.V. Zaryanov, O.G. Voronin, E.E. Karyakina, A.K. Yatsimirsky, A.A. Karyakin. Anal. Chem. 2014, 86, 11690–11695 Financial support through Russian Science Foundation grant # 16-13-00010 and MSU grant # 013-05/16 are greatly acknowledged.