Effect of Temperature and Additives on the Interaction of Ciprofloxacin Hydrochloride Drug with Polyvinylpyrrolidone and Bovine Serum Albumin: Spectroscopic and Molecular Docking Study.

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 UVvisible and fluorescence spectroscopic methods at different temperatures. The binding constant (K ) 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) were used for the interaction between CFH and PVP. The gradual increase in K value and the complexation reaction was found to be much enhanced with the augmentation of the MW of PVP. The values of K 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 (∆G ) values of the interaction process was negative which indicates the complex formation is thermodynamically spontaneous. The positive values of enthalpy (∆H ) and entropy (∆S ) 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 ) 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 (K ), quenching constant (K ), the number of binding sites (n), and the quenching rate constant (K ) for the CFH-BSA system were also calculated. The values of K , K , and n for the CFH-BSA system are lower in 0.05 mol L urea solution and higher in PVP solutions compared to those of aqueous medium.