Effect of pH and ionic strength of chitosan/casein and casein/chitosan multilayers on curcumin release

Abstract

In the present paper the effect of pH and ionic strength on the immobilization and release of curcumin from chitosan and casein polyelectrolyte multilayers (PEMs) was investigated. The investigated PEMs were deposited on polylactic acid (PDLA) substrates. The PLA substrates were charged in a corona discharge system, consisting of a corona electrode, a grounded plate electrode and a grid placed between them. The substrate was charged for 1 minute at room temperature. Positive or negative 5kV voltage was applied to the corona electrode and 1 kV voltage with the same polarity was applied to the grid. Chitosan solutions with different pH and ionic strength were prepared. Layer-by-Layer (LbL) deposition technique was used for the multilayer build-up. For the deposition process was ensured that the first deposited layer always possessed an opposite electric charge to that of the substrate. An investigation of the water uptake properties of the deposited PEM multilayers was carried out. Curcumin was immobilized in the resulting casein layers. The release of the immobilized curcumin from the multilayers in saline buffer was investigated and the effects of the different pH and ionic strengths of the chitosan solutions were determined.