Interaction of Amphiphilic Propranolol Hydrochloride with Haemoglobin and Albumin in Aqueous Solution

Abstract

ζ-potential and UV difference spectroscopy techniques have been utilized to study the interaction of the amphiphilic drug propranolol hydrochloride with human haemoglobin (HH) and human serum albumin (HSA) in aqueous solution at pHs below, above, and at the isoelectric points of both proteins at 25 °C. The number of adsorption sites on both proteins was determined from the observed increases of the ζ-potential as a function of drug concentration in the regions of positive ζ-potential, where the adsorption was a consequence of the hydrophobic effect. The Gibbs energies of adsorption of the drug onto the proteins showed an exponential decrease with increase of drug concentration. The interactions between HSA−propranolol complexes in the presence of propranolol hydrochloride were interpreted from dynamic light-scattering data using the Derjaguin−Landau−Verwey−Overbeek (DLVO) theory. The concentrations of the amphiphilic drug were maintained below its critical concentration, so its behavior could be considere...