Pyrazoline based chloride sensor for body fluids screening Andreea L. Chibac, Gheorghe Roman, Corneliu Cojocaru, Gabriela Sacarescu, Mihaela Simionescu, Liviu Sacarescu ⁎ Petru Poni Institute of Macromolecular Chemistry, 41 A Grigore Ghica Voda Alley, 700487 Iasi, Romania abstract article info Article history: Received 14 January 2019 Received in revised form 26 March 2019 Accepted 2 April 2019 Available online 03 April 2019 The fluorescence detection of different electrolytes existing in body fluids represents a modern method for diag- nosis of diseases. This work reports the use of a pyrazoline derivative as a new fluorescence chloride sensor based on a dynamic quenching mechanism. Moreover, we show that 1,3-diphenyl-5-{4-[(4-vinylbenzyl)oxy]phenyl}- 4,5-dihydropyrazole is capable to detect multiple halides and behave differently depending on the nature of ei- ther the halide or the metal counterion. The optical properties of this pyrazoline in the presence of halides of al- kaline and several transitional metals have been determined by UV–Vis and FL measurements in solution. Stern- Volmer equation used for fluorescence data analysis revealed interesting particularities depending on the se- lected quencher. We discovered that the aforementioned pyrazoline is highly sensitive to potassium chloride or iodide, but, is inert to potassium bromide. Quantum mechanical calculations were employed to generate the molecular models of the pyrazoline in ground and excited state, with the view to obtain the HOMO-LUMO energy gap and mapped electrostatic isopotential. Thus, it was possible to explain the sensitivity for chloride and estab- lish the fluorescence quenching mechanism. This pyrazoline derivative may be used to expand the class of fluo- rescent materials with improved chloride sensitivity and develop multi analysis systems. © 2019 Published by Elsevier B.V. Keywords: Pyrazoline Sensor Fluorescence Chloride Diagnostic fluid 1. Introduction Fluorescence sensing allows spatially and temporally measurements of ionic concentration down to the cellular level [1–3]. Nowadays, this approach is a significant method in research and in the monitoring of some important medical conditions [4]. The technique is highly sensi- tive, very easy to apply, and could be therefore used in medical screen- ing to discover early signs of various pathologies. From this point of view, there is a continuously growing interest related to the screening of human body fluids [5]. Medical fluorescence tests could be performed to reveal modifications of the chemical composition of body fluids, tests that are based either on the presence/absence or on the excess/lack of specific analytes [6]. Moreover, the fluorescence detection of a particu- lar biocomponent is also important during different stages of illness in order to monitor the efficiency of the treatment [7–11]. Health evalua- tion and therapeutic screenings based on body fluid analysis provide an important amount of information required prior to reaching the cor- rect medical decision [12]. Chloride determination is necessary for diagnosis of medical condi- tions related to metabolic dysfunctions and electrolyte imbalance, such as diabetic acidosis and cystic fibrosis [13,14]. In this regard, current investigation methods are still expensive and especially inva- sive because they rely on intrusive procedures for sample collection var- ious body fluids, but mostly of blood. On the other hand, other bio-fluids are readily accessible, easy to collect by non-invasive ways and less predisposed to contamination than blood, the most common being sweat and saliva [15]. Analysis of these bio-fluids is also useful, as a re- lationship between the chloride content in human saliva and cystic fi- brosis has been recently established [16,17], while the well-known method applied in cystic fibrosis diagnosis is the sweat test. However, the reliability of the latter test depends on multiple variable factors, such as sex, age, ethnicity, weight, cystic fibrosis transmembrane con- ductance regulator (CFTR) mutations, body composition, the influence of other ion channels, or alternative chloride channels [18,19]. Measure- ment of chloride in saliva avoids these variables because the composi- tion of saliva should be the same for normal people. Thus the normal average concentration of chloride anions in saliva is usually around 22.6 mmol/L, the normal limits varying from 11.2 mmol/L to 44.7 mmol/L. In the case of medical conditions that entail modification of chloride content in saliva, the concentration could be outside the range aforementioned [20]. Research in this field proved that CFTR mu- tations could be evidenced by abnormal concentrations of chloride ions [21]. Therefore, the chloride level in saliva is indicative for the presence of the cystic fibrosis in early stage of development. This type of diagnosis method is very promising, and intensive research is under way in order to clarify some particular aspects. Journal of Molecular Liquids 284 (2019) 139–146 ⁎ Corresponding author. E-mail address: livius@icmpp.ro (L. Sacarescu). https://doi.org/10.1016/j.molliq.2019.04.007 0167-7322/© 2019 Published by Elsevier B.V. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq