DEVELOPMENT OF A WASHLESS APPROACH FOR LAYER-BY-LAYER ASSEMBLY UPON RESVERATROL NANOCORES

António J. Ribeiro, A.C. Santos, F. Veiga and C. Fontes Ribeiro

Department of Development and Drug Technologies, University of Coimbra, Coimbra, Portugal

Abstract

Resveratrol (RSV) is a polyphenol with wide documented therapeutic properties, which are, yet, strongly compromised by its physicochemical properties, thus demanding for strategic encapsulation technologies. Layer-by-Layer (LbL) assembly is an advanced functionality based on nanocoatings construction with variable compositions and thickness. RSV-loaded LbL nanoparticles (RSVNP) were herein developed with no use of time-consuming and losses-promoting polyelectrolyte intermediate washings. Newly and detailed characterizations of the LbL shell were performed by the sequential adsorption of poly(allylamine hydrochloride) (PAH) (polycation) and dextran sulphate (DS) (polyanion) upon the surface of RSV nanocores obtained previously by nanoprecipitation. Sufficient polyelectrolyte concentrations for each coating layer deposition were assessed by tracing polyelectrolyte titration curves. This procedure consisted in the testing of a polyelectrolyte concentration range for each polyelectrolyte layer accomplishment, while monitoring zeta-potential and particle size values. The complete deposition of a layer was suggested by the recharging point of each titration curve, identified as the requisite to proceed for the next polyelectrolte layer deposition. Different fitting models were found for PAH and DS titration profiles, which were attributed to the difference in polyelectrolytes charge density. Stable aqueous RSVNP with 2.5, 5.5 and 7.5 PAH/DS bilayers were formulated resorting to a scalable and promising washless approach.

Keywords: Resveratrol, Layer-by-Layer, nanoparticle, washless, titrations.