Complexation behavior of gelatin with amphiphilic drug imipramine hydrochloride as studied by conductimetry, surface tensiometry and circular dichroism studies

Herein we report our studies carried out on the Inter action between IMP and gelatin in aqueous medium at 25 C using conductimetry surface tensiometry and circular dichroism (CD) techniques Both surface tensiometry and conductimetry results indicate that the drug interacts with the gelatin in a surfactant like manner i e both critical aggregation (cac) and polymer saturation points (psp) were observed The interaction starts with the formation of a highly surface active complex as revealed by the lowering of surface tension on the addition of drug to the macromolecule The decrease in cac on increasing gelatin concentration is an indication of the strong interaction between gelatin and IMP However at low con centration of gelatin the interaction was not much strong as exposed by surface tension study le the cac was not very clear (as with higher gelatin concentrations) As usual the psp increased on increasing the gelatin concentration and was always higher than the critical micelle concentration of the drug in pure aqueous medium Using CD measurements the influence of IMP on the secondary structure of gelatin in aqueous solutions was also investigated CD studies (performed at very low drug concentrations) illustrated that the random coil content of gelatin increases with increasing drug concentration Free energies of aggregation (Delta G(agg)) and micellization (Delta G(mic)) were computed with the help of degrees of micelle ionization obtained from the specific conductivity - [IMP] plots (C) 2010 Elsevier B V All rights reserved