Paper published: Composition and charge compensation in chitosan/gum arabic complex coacervates in dependence on pH and salt concentration

Today, Philipp Schröder’s second publication in collaboration with Dr. Stefan Cord-Landwehr has been published in the renowned journal Biomacromolecules. Philipp is a doctoral candidate in the group of Prof. Dr. Monika Schönhoff from the Institute of Physical Chemistry and the Center for Soft Nanoscience of our University, supervised by PD Dr. Cornelia Cramer from the same institute. Philipp had contacted us earlier asking for well-characterised chitosans for his research project on coacervates of positively and negatively charged polymers. This initiated a collaboration which, as a first step, included improving methods to analyse the purity of chitosan solutions. As rather surprisingly, there are very few reliable tools for this important analysis, we published [B2] this method jointly. Then only, Philipp and Stefan were able to approach the real question, namely trying to understand the formation of coacervates – rather than precipitates or co-solutions – of positively charged chitosan and negatively charged gum arabic. This is a highly complex process, especially in the case of two interacting biopolymers rather than more simple synthetic polymers. The interaction between the two polyelectrolytes can be expected to be governed by the strength of the opposite charges and their electrostatic interactions, which in turn can be influenced by the salt concentration and the pH value of the solvent. Philipp succeeded, for the first time, in quantitatively describing the influence of pH-induced extrinsic charge compensation in terms of the doping level which traditionally is used to describe the influence of salt-induced extrinsic charge compensation. Such quantitative understandings are highly relevant for the development of e.g. drug or vaccine delivery systems using nanoparticles based on sustainable and biocompatible biopolymer coacervates.