Controled loading and release of model drugs from polyelectrolyte multilayer thin films

Abstract

The Layer-by-Layer (LbL) self assembly technique of polyelectrolyte multilayers (PEM) has shown great potential in bio-coating material as well as local drug delivery systems. Herein, combination of positively charged polyelectrolyte of poly(diallyldimethylammonium chloride) (PDADMAC) or chitosan (Chi) and negatively charged polyelectrolyte of poly(sodium 4-styrenesulfonate) (PSS) or poly(4-styrene sulfonic acid-co-maleic acid, sodium salt) (PSSMA) were constructed and used as polymer matrix and coatings for control release of various drugs. Structure, thickness, roughness and stability of the PEM films were characterized by uv-vis spectrophotometer and AFM measurement. Model drugs (curcumin, diclofenac sodium and gentian violet) were incorporated in the polymer matrix and their loading and release behavior was quantified by uv-vis spectrophotometer as a function of the external media. The loading of the model drugs was achieve through hydrophobic interaction or electrostatic interaction and controlled by solution media characteristics such as solvent composition, pH, ionic strength but also loading time and number of constructed layers. Differences in polymer matrix structures have been found to influence the loading and release behavior under otherwise fixed conditions. Results indicated that the release of curcumin was affected by changing the solvent composition of water/ethanol and ionic strength while the release of diclofenac sodium and gentian violet was most affected by the pH and ionic strength of the loading medium. The polymer matrix of PDADMAC/PSS, PDADMAC/PSSMA and Chi/PSS can therefore be used as drug reservoir for the controlled loading of functional molecules and their release. In addition, PEM blocking layer deposited on top of polymer matrix were used to prolong the slow release of curcumin from PEM matrix substrates when exposed to physiological buffer. The blocking films was constructed by the LbL self assembly of positively charged of chitosan (Chi) and negatively charged of alginate (Alg) or poly acrylic acid (PAA). Both blocking films delayed the release of curcumin when compared to a PDADMAC/PSS blocking film with the Chi/Alg film being the most efficient. Finally, in an attempt to explore an innovative application of drug loaded PEM films, fruit were coated with PEM films and loaded with curcumin was used to quantify the amount of curcumin loaded at the surface of the fruit.