Interaction studies of levofloxacin with human lysozyme in a ternary complex using multispectroscopic and computational analysis: A circular dichroism method for the quantitation of levofloxacin

Abstract

In this study, a ternary complex for levofloxacin determination in human lysozyme using the lacosamide as a binary component was employed. The ternary complex caused a decrease in fluorescence intensity of lysozyme by 31.51 % while in case of levofloxacin interaction alone with lysozyme, fluorescence intensity decreased by 54.58 %. This suggested that levofloxacin binding in a ternary complex produced less microenvironmental changes in lysozyme. The spectroscopic approach has been reported where fluorescence, UV–visible, synchronous fluorescence and circular dichroism was used to know the structural changes in lysozyme after its interaction with levofloxacin (8.85–34.80 μgmL-1). Box-Behnken design under response surface methodology was opted to optimize the experimental variables. The results from the molecular docking after structure optimization with DFT inferred that lacosamide did not compete with levofloxacin for amino acid residues. Thus, revealing the possibility of co-administration of these drugs in clinical studies. Circular dichroism method was used to model the calibration curve that was constructed between ellipticity (millidegree) as a function of wavelength vs concentration. The linearity lies in the range of 4–32 μgmL-1. The developed method is simple, sensitive, accurate and selective for the estimation of levofloxacin with a limit of detection of 0.42 μgmL-1 and limit of quantification of 1.26 μgmL-1. The recovery data ranged from 99.56 − 101.23 % and 99.1–100 % for intra- and inter-day precision, respectively. The developed method was applied in dosage forms having less than 2 % relative standard deviation and displayed outstanding sensitivity towards dosage forms, thus revealing its potential application.