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. 2023 Nov 1;8(45):42699-42710.
doi: 10.1021/acsomega.3c05100. eCollection 2023 Nov 14.

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis

Abrar Siddiquee  1 , Zahoor Parray  2 , Aashima Anand  1 , Shadma Tasneem  3 , Nazim Hasan  3 , Waleed M Alamier  3 , Abeer A Ageeli  3 , Farooq Ahmad Wani  1 , Prashant Singh  4 , Rajan Patel  1
Affiliations

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis

Abrar Siddiquee et al. ACS Omega. .

Abstract

Herein, we have shown the interaction of an antibiotic drug ciprofloxacin (CIP) with three surface-active ionic liquids (ILs), having the same cation and different anions, namely, 1-decyl-3-methylimidazoliumtetrafluoroborate [C10mim][BF4], 1-decyl-3-methylimidazolium bromide [C10mim][Br], and 1-decyl-3-methylimidazolium chloride [C10mim][Cl]. This study has been performed by exploiting various spectroscopic techniques such as steady-state fluorescence, time-resolved fluorescence, and UV-visible spectroscopy. The fluorescence emission study of CIP with ILs was performed at various concentrations of all the three ILs. The emission spectra of CIP decreased in the presence of ILs, suggesting complex formation between CIP-IL. The effect of different concentrations of ILs on the emission spectra of CIP was exploited in terms of quenching and binding parameters. Further, fluorescence emission study was validated by the time-resolved fluorescence technique by measuring the average lifetime (τavg) of CIP in the presence of all the three ILs. The τavg value of the drug changed with the addition of ILs, which suggests complex formation between the drug and ILs. This complex formation was also confirmed by UV-visible spectroscopy results of CIP with all the three ILs. Further, for evaluating the thermodynamic parameters of the CIP-IL interactions, isothermal titration calorimetry (ITC) was performed. The ITC experiment yielded the thermodynamic parameters, ΔH (change in the enthalpy of association), ΔG (Gibbs free energy change), ΔS (entropy change), and binding constant (Ka). The binding parameters driven by ITC revealed that CIP-IL interactions are spontaneous in nature and enthalpy-driven, involving hydrophobic forces. Further, the classical density functional theory (DFT) calculations were performed, which provided deep insight for CIP-IL complex formation.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Fluorescence emission spectra of CIP (20 μM, λmax = 274 nm) in the presence of [C10mim][BF4] (A), [C10mim][Br] (B), and [C10mim][Cl] (C).
Figure 2
Figure 2
Stern–Volmer plots (A) and plots of log(F0 −F/F) vs log C (B) of CIP in the presence of [C10mim][BF4], [C10mim][Br], and [C10mim][Cl].
Figure 3
Figure 3
Time-resolved fluorescence spectra of CIP (20 μM) in the presence of [C10mim][BF4] (A), [C10mim][Br] (B), and [C10mim][Cl] (C).
Figure 4
Figure 4
Absorption spectra of CIP (20 μM) as a function of (A) [C10mim][BF4], (B) [C10mim][Br], and (C) [C10mim][Cl] concentration.
Figure 5
Figure 5
Isothermal calorimetric binding of CIP with titration of (A) [C10mim][BF4], (B) [C10mim][Br], and (C) [C10mim][Cl] and their respective calorimetric responses.
Figure 6
Figure 6
Frontier molecular orbitals (HOMO and LUMO) and optimized geometry of CIP, ILs, and their complexation in the gaseous state at 298 K.
Figure 7
Figure 7
Frontier molecular orbitals (HOMO and LUMO) and optimized geometry of CIP, ILs, and their complexation in the water medium at 298 K.
Scheme 1
Scheme 1. Structures of ILs and the Drug Used in the Study
See this image and copyright information in PMC

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