ISSN 2411-958X (Print) ISSN 2411-4138 (Online) European Journal of Interdisciplinary Studies January-April 2016 Volume 2, Issue 1 100 Polyelectrolyte Complexes Based on Chitosan and Natural Polymers Alef Mustafa Umf Carol Davila Bucharest, Faculty of Pharmacy, Traian Vuia Str. Nr. 6, Sector 2, Bucharest, Romania Aneta Tomescu "Ovidius" University of Constanţa, Faculty of Medicine, Campus Corp B, University Alley, Nr. 1, Constanta, Romania Emin Cadar Umf Carol Davila Bucharest, Faculty of Pharmacy, Traian Vuia Str. Nr. 6, Sector 2, Bucharest, Romania Melat Cherim Umf Carol Davila Bucharest, Faculty of Pharmacy, Traian Vuia Str. Nr. 6, Sector 2, Bucharest, Romania Rodica Sîrbu "Ovidius" University of Constanţa, Faculty of Pharmacy, Campus Corp B, University Alley, Nr. 1, Constanta, Romania Corresponding author: Rodica Sirbu; sirbu_27@yahoo.com Abstract For many years chitosan has been the subject of interest for its use in different medical fields due to its appealing properties such as biocompatibility, biodegradability, low toxicity and relatively low production cost from abundant natural sources. Chitosan is positively charged at low pH values, so it is spontaneously associated with negatively charged polyions in solution to form polyelectrolyte complexes. These chitosan based polyelectrolyte complexes exhibit favourable physicochemical properties with preservation of chitosan’s biocompatible characteristics. These chitosan based complexes are a good candidate for excipient materials for the design of different types of dosage forms. The aim of this review is to describe polyelectrolyte complexes of chitosan with selected natural polyanions and also to indicate some of the factors that influence the formation and stability of these formed complexes. Keywords: chitosan; polyelectrolyte complex; natural polymers INTRODUCTION Chitosan is a combination of a series of polymers that are deacetylated derivatives of chitin,a natural polysaccharide,and presents different degrees of deacetylation and molecular weights. It consists of deacetylated units of β-1,4-linked glucosamine and acetylated units of N-acetyl-D-glusoamine (Figure 1). Chitosan presents typical degrees of deacetylation between 70 and 95% and molecular weights between 10 and 1,000 kDa [1,2] . It was reported that highly refined grades of chitosan have been used in pharmaceutical formulations as a release-controlling agent [3]. It was shown that the cationic amino groups on the C2 position of the repeating glucopyranose units of chitosan can interact electrostatically with the anionic groups (usually carboxylic acid groups) of other polyions to form polyelectrolyte complexes. Many different polyanions from natural origin (e.g. pectin, alginate, carrageenan, xanthan gum, carboxymethyl cellulose, chondroitin sulphate, dextran sulphate, hyaluronic acid) or synthetic origin (e.g., poly (acrylic acid)), polyphosphoric acid, poly (L-lactide) have been used to form polyelectrolyte complexes with chitosan in order to provide the required physicochemical properties for the design of specific pharmaceutical formulations [4]. Thoughout the years chitosan complexes have been used in a wide range of pharmaceutical applications such as complexes formed between chitosan and anionic polymers for use as biosensors, scaffolds in tissue engineering, for waste- water treatment and for drug delivery in different forms [5,6].