Self-Organization of Mobile, Polyelectrolytic Dendrons on Stable, Amphiphile-Based Spherical Surfaces.

Abstract

Spherical surfaces bearing mobile, solvophilic chains are ubiquitous. These systems are found in nature in the form of biological cells bearing carbohydrate chains, or glycans, or in drug delivery systems such as vesicles bearing polyethylene glycol chains and carrying therapeutic molecules. The self-organization of the chains on the spherical surface dictates the stability and functionality of the latter and is determined by key factors such as the interchain, chain-surface interactions, excluded volume, concentration of the chains, and external environment. This study develops a fundamental understanding of how these factors control the organization of mobile, solvophilic chains while preserving the stability of the spherical surface. To that end, the study focuses on the organization of polyamidoamine dendrons on the surface of a dipalmitoylphosphatidylcholine-based vesicle. The excluded volume of the chains and the external environment are, respectively, controlled via the dendron generation and the pH. For acidic and basic pH environments, the dendrons are extended away from the surface. As a consequence, the vesicles are able to accommodate significantly higher concentration of dendrons on their surface without rupturing. For acidic pH, the dendrons change their conformation to avoid intermeshing. However for basic pH, the dendrons only change their conformation at extremely high concentrations due to excluded volume effects. These conformational changes are attributed to the number of protonated dendron residues that vary as a function of pH. The results from this study will advance diverse subdisciplines within cell biology, biomedicine, and pharmaceuticals.