Detection of Anti-viral Drug Riamilovir and Herbicides in Aqueous Media by Using Pyrene-based Fluorescent Chemosensors Chimica Techno Acta LETTER published by Ural Federal University 2021, vol. 8(2), № 20218208 eISSN 2411-1414; chimicatechnoacta.ru DOI: 10.15826/chimtech.2021.8.2.08 1 of 3 Detection of Anti-viral Drug Riamilovir and Herbicides in Aqueous Media by Using Pyrene-based Fluorescent Chemosensors I.S. Kovalev a , L.K. Sadieva a,b,* , O.S. Taniya a,b , D.S. Kopchuk a,b , G.V. Zyryanov a,b , E.N. Ulomsky a,b , V.L. Rusinov a,b , O.N. Chupakhin a,b a: Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia b: Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, 22 S. Kovalevskoi / 20 Akademicheskaya St., Yekaterinburg 620219, Russia * Corresponding author: leilasad@yandex.ru This short communication (letter) belongs to the regular issue. © 2021, The Authors. This article is published in open access form under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Abstract Two ethyleneglycol esters of 1-pyrene carboxylic acid were studied as chemosensors for the fluorescence “turn-off” detection of two ni- tro-containing analytes, such as antiviral drug Riamilovir (Triazavi- rin ®) and herbicidal agent dinitro-ortho-cresol (DNOC). In both cas- es the dramatic fluorescence quenching was observed with quench- ing constants as high as 3·10 4 M -1 and limits of detection (LOD) as low as 100 ppb. Keywords COVID-19 Riamilovir (Triazavirin ®) DNOC detection in aqueous media chemical sensors pyrene-based fluorophores fluorescence quenching Received: 19.04.2021 Revised: 30.04.2021 Accepted: 18.05.2021 Available online: 20.05.2021 1. Introduction One of the scourges of modern civilization is the corona- virus (SARS-CoV-2) pandemic that broke out in the end of the 2019. Despite the fact that the antiviral drug Riami- lovir (Triazavirin ®) is not a specific drug against SARS- CoV-2, it has successfully shown itself among other drugs in reducing the incidence of respiratory, cardiac, hepatic, renal and other complications, associated with corona- virus infection (COVID-19) [1,2]. For the pharmacokinetic studies of this drug as well as other ones, it is very im- portant to determine the fate of these substances, admin- istered to a living organism. Once drugs are administered their concentration in target organs or biological liquids is changed. Fluorescence-based methods are the robust and convenient methods of measuring drug concentration in the biological (water-based) liquids and target organs [3,4]. In addition to coronavirus infection, the problem of soil, air and rain pollution with herbicides and their decay products, has long been an acute problem [5]. Despite the fact that at present in Europe and the United States the use of such herbicide as Dinitro-ortho-cresol (DNOC) is abandoned, accumulated over the years of previous use, it is still present [5,6]. DNOC has been identified in at least 56 of the 1854 hazardous waste sites that have been pro- posed for inclusion on the EPA National Priorities List (NPL) [6]. It is also still widely used in Russia and other countries. In this manuscript we would like to report our study of sensory abilities of the pyrene-based polyethyleneglycol water-soluble fluorescent “turn-off” chemosensors toward nitro-containing drug Riamilovir and herbicide DNOC. 2. Experimental Chemosensors 1-2 (see Fig. 1) were obtained as reported earlier [7]. Starting materials are commercially available. Fluorescence titration experiments were carried out by using the Horiba-Fluoromax-4 spectrofluorometer (USA). Solutions of sensors 1-2 with concentration 10 -6 M in H2O : THF (99.9 : 0.1 (v/v)) and solutions of quenchers with concentration 10 -4 M in water (Riamilovir) and in acetoni- trile (DNOC) were prepared. Next, fluorescence quenching http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.08 http://creativecommons.org/licenses/by/4.0/ Chimica Techno Acta 2021, vol. 8(2), № 20218208 LETTER 2 of 3 Fig.1 Structure of chemosensors 1-2 was carried out via the method of Single Point [8]. The solution of sensor by volume of 3 ml was placed in quartz cuvette and intensity of its fluorescence was measured. After that 15 aliquots of solution of quencher (volume of each aliquot was 10 mkl) were added into cuvette one by one. After each addition of quencher, fluorescence intensi- ty was measured. Analysis of fluorescence quenching was performed on the basis of a Stern-Volmer equation of static quenching (1): 𝐼0 𝐼 = 1 + 𝐾SV [Q] . (1) The Stern-Volmer constants (Ksv) were calculated as the slope of the intensity plot (((𝐼0/𝐼) − 1)) versus the con- centration of the quencher ([Q]). 3. Results and Discussion As water soluble chemosensors, two pyrene-based chemosensors 1-2 (Fig. 1) were selected, and their synthe- sis and photophysical properties were reported earlier [7]. Based on these previous studies, chemosensors 1-2 have exhibited high sensitivity toward some common nitro- explosives, such as 2,4,6-trinitrotoluene (TNT) and pen- taerythritol tetranitrate (PETN) in aqueous media. So, we expected that these molecules will be suitable candidates for the detection of nitro-containing Riamilovir and DNOC. To study sensory abilities of sensors 1-2 towards the abovementioned nitro-analytes, fluorescence quenching titration was carried out. The fluorescence response was quantitatively determined via the Stern-Volmer static quenching model, according to Eq. (1). The Stern-Volmer constant values for Riamilovir were calculated to be as high as Ksv = 2.67·10 4 M -1 and 2.28·10 4 M -1 for the sensors 1 and 2, respectively, and, based on the linearity of the Stern-Volmer plots, the static quenching (Table 1, Fig. 2A,B) was suggested. Fig. 2 Stern-Volmer plots of emission quenching for sensors 1 (A, C) and 2 (B, D): points – experimental data, lines – linear fitting results Chimica Techno Acta 2021, vol. 8(2), № 20218208 LETTER 3 of 3 Table 1 Summary of the Stern-Volmer rate constants and LOD for the chemosensors 1-2 Sensor KSV Riamil. , M -1 KSV DNOC , M -1 LOD Riamil. , ppb LOD DNOC , ppb 1 2.67·10 4 3.07·10 4 101 122 2 2.28·10 4 3.14·10 4 252 223 Under similar conditions, DNOC caused a slightly stronger response, which can be seen based on higher val- ues of Stern-Volmer constants, such as Ksv = 3.07·10 4 M -1 (for the sensor 1) and Ksv = 3.14·10 4 M -1 (for the sensor 2) (Table 1). Again, linearity of Stern-Volmer plots was ob- served. In addition to linear behavior of Stern-Volmer plots, high values of the coefficient of determination (R 2 ) were obtained (Fig. 2). Thus, the prevalence of only one quench- ing mechanism, such as static quenching, in all the cases was suggested. For all titration experiments, limits of detection (LOD) were calculated by using previously reported methods [9]. LOD values are collected in Table 1. 4. Conclusions Ethyleneglycol esters of 1-pyrene carboxylic acid were found to be promising chemosensors for the fluorescence “turn-off” detection of nitro-containing drugs, such as Ri- amilovir, and ecotoxicants, such as dinitro-ortho-cresol, in aqueous solutions. In all the cases, dramatic fluorescence quenching and high quenching constants (2.28·10 4 – 3.14·10 4 M -1 ) were observed. Acknowledgements This work was supported by the Russian Foundation for Basic Research (Project № 19-33-90155). References 1. Wu X, Yu K, Wang Y, Xu W, Ma H, Hou Y, et al. Efficacy and Safety of Triazavirin Therapy for Coronavirus Disease 2019: A Pilot Randomized Controlled Trial. Engineering. 2020;6(10):1185–91. doi:10.1016/j.eng.2020.08.011 2. Sabitov AU, Belousov VV, Edin AS, Oleinichenko EV, Gladu- nova EP, Tikhonova EP, et al. Practical experience of using ri- amilovir in treatment of patients with moderate COVID-19. Antibiotiki i Khimioterapiya. 2020;65(7–8):27–30. Russian. doi:10.37489/0235-2990-2020-65-7-8-27-30 3. Ayoob AM, Peppi M, Tandon V, Langer R, Borenstein JT. A fluorescence-based imaging approach to pharmacokinetic analysis of intracochlear drug delivery. Hear Res. 2018;368:41–8. doi:10.1016/j.heares.2018.03.026 4. Kuneš M, Květina J, Maláková J, Bureš J, Kopáčová M, Rejchrt S. Pharmacokinetics and organ distribution of fluorescein in experimental pigs: An input study for confocal laser endomi- croscopy of the gastrointestinal tract. Neuroendocrinol Lett [Internet]. 2010;31(Suppl. 2):57–61. 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