Abstract
The fluoroquinolone antibiotic drug namely ciprofloxacin hydrochloride (CFH) is widely prescribed for the treatment of different bacterial infections. The interaction of CFH with a synthetic polymer, polyvinyl pyrrolidone (PVP), and biopolymer, bovine serum albumin (BSA) was studied by UV-visible and fluorescence spectroscopic methods at different temperatures. The binding constant (Kb) for the CFH-PVP complex was determined from the Benesi-Hildebrand plot. PVP of different molecular weights (MW) (such as 24,000, 40,000, 360,000, and 700,000 g. mole?1) were used for the interaction between CFH and PVP. The gradual increase in Kb value and the complexation reaction was found to be much enhanced with the augmentation of the MW of PVP. The values of Kb were also found to be increased with increasing temperatures as well as with the increase of electrolyte/acetic acid concentration. The Gibbs free energy of binding (?G0) values of the interaction process was negative which indicates the complex formation is thermodynamically spontaneous. The positive values of enthalpy (?H0) and entropy (?S0) of binding connote that the binding force for CFH-PVP complexation is hydrophobic in nature and the complexation is entropy controlled. The negative intrinsic enthalpy (?H*,0) values indicate the high stability of CFH-PVP complexes. Molecular docking calculation discloses the existence of similar binding forces between CFH and PVP obtained by the analysis of experimental data from UV-visible spectroscopic method. The binding constant between CFH and BSA (Kb), quenching constant (Ksv), the number of binding sites (n), and the quenching rate constant (Kq) for the CFH-BSA system were also calculated. The values of Ksv, Kq, and n for the CFH-BSA system are lower in 0.05 mol L?1 urea solution and higher in PVP solutions compared to those of aqueous medium.