Role of non-ionic surfactant on the interaction of drugs with bovine serum albumin (BSA)

Serum albumins are the soluble protein part in the circulatory system. They have a significant role in transport and delivery of drug in blood. Bovine serum albumin (BSA) is generally used as model protein which is structurally similar to human serum albumin. Interaction of drug at the protein binding level can induce many changes like distribution rate, elimination of drug or most importantly solubilisation of a hydrophobic drug. Protein–surfactant interaction employed to cause conformational changes in protein by change of polarity and on many occasions help in stabilisation of protein. Generally, non-ionic surfactants are used for these purposes and hence are widely studied. The studies on drug binding with BSA in presence of non-ionic surfactant are, however, rare in literature. In this study, four drugs are taken for analysing their binding with BSA in presence of a non-ionic, hydrophobic surfactant, pluronic L-81, and investigate their role in the system. The drugs are tinidazole, piroxicam, methylparaben and propylparaben. The characterisations were done using UV–visible spectroscopy and fluorescence spectroscopy. The UV spectroscopic measurements were conducted for BSA–drug mixtures without and with pluronic L-81. The absorbance values were used for determining the binding constant values using Benesi–Hildebrand (B-H) plot. Fluorimetry studies of the BSA + L-81 + drug mixtures were carried out at room temperature which showed that there was quenching effect on addition of drug to BSA + L-81 mixture. Furthermore, the quenching was of dynamic nature. The fluorescence data were analysed using Stern–Volmer and Lineweaver–Burk equations. With the data, association constant KA for all the systems were determined. The docking studies confirmed the binding of the drugs with BSA.