title: The impact of polyelectrolyte structure on the shape of nanoassemblies with cationic peptides.
abstract: We investigated how the structure of nanofibers, resulting from interactions between anionic polyelectrolytes and cationic peptides, relies on the properties of the polyelectrolyte component. By using hyaluronate (H), carboxymethylcellulose (CMC), xanthan (X), and ozarelix (O), a cationic decapeptide, we determined the influence of characteristic polyelectrolyte parameters such as size and charge density on the formation of polyelectrolyte-peptide complexes. Transmission electron microscopy of unstained, frozen hydrated, or negatively stained samples revealed that the interaction between different anionic polyelectrolytes and ozarelix led to the formation of distinctly shaped nanofibers. CMC formed rather flexible structures with alternating thin and thick segments within the nanofibers with diameters ranging from 10 to 16 nm and a length of up to 1 μm. Hyaluronate, a high-molecular-mass molecule, formed extra-long aggregates of more than 5 μm. Individual fibers with a diameter of 8 nm aggregated to bigger strands. The nonlinear polysaccharide xanthan gum led to highly coiled structures. The diameter of the respective nanofibers varied between 15 and 25 nm. Isothermal titration calorimetry was used to determine the binding constants and the thermodynamic parameters of the different polyelectrolyte-peptide complexes. The binding constant, which was of the order of 10(6) M(-1) , indicated a strong binding affinity, but also showed differences among the polyelectrolytes. These differences might be useful for prospective applications as drug delivery systems.
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Regensburg 93053, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ferstl
authors.forename: Markus
authors.initials: M
authors.lastname: Drechsler
authors.forename: Reinhard
authors.initials: R
authors.lastname: Rachel
authors.forename: Matthias
authors.initials: M
authors.lastname: Rischer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Engel
authors.forename: Michael
authors.initials: M
authors.lastname: Backofen
authors.forename: Achim
authors.initials: A
authors.lastname: Goepferich
mesh_terms: D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D002412:Cations / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry; D006820:Hyaluronic Acid / Q000737:chemistry; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D009842:Oligopeptides / Q000737:chemistry*; D010316:Particle Size; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D002412:Cations; D004573:Electrolytes; D009842:Oligopeptides; D011135:Polysaccharides, Bacterial; D006820:Hyaluronic Acid; D002266:Carboxymethylcellulose Sodium; C556865:ozarelix; C002563:xanthan gum
keywords: calorimetry (ITC); imaging methods; nanotechnology; particle size; physical characterization; polyelectrolytes; protein formulation