Colloidal complexes from associated water soluble cellulose derivative (methylcellulose) and green tea polyphenol...

The present work deals with the preparation and characterisation of colloidal complexes from association of water soluble cellulose derivative (methylcellulose) and green tea polyphenol-EGCG (Epigallocatechin gallate). Colloidal complexes with well defined size range of 95-300 nm (polydispersity index<0.15) and a negative surface potential (-25 to -45 mV) were obtained by mixing solutions of methylcellulose and EGCG under vigorous stirring. The binding stoichiometry of 21 molecules of EGCG per one molecule of polymer was obtained from isothermal titration calorimetry. The free energy of binding (-31 kJ mol(-1)) is dominated by the binding enthalpy suggesting that the non-covalent complex is preferentially formed due to the hydrogen bonding. Transmission electron microscopy revealed almost spherical particle morphology of the formed colloidal complexes. Further, sustained release of EGCG from the complex in simulated in vitro media was observed which resulted in protecting the antioxidant property of EGCG in alkaline pH.