Polyelectrolyte complexes from polysaccharides: formation and stoichiometry monitoring.
ABSTRACT Colloids were obtained from non-stoichiometric polyelectrolyte complexes with two polysaccharides of opposite charge: chitosan and dextran sulfate (DS) as the polycation and polyanion, respectively. The complexes were elaborated by a one-shot addition of the polymer in default to the one in excess. The colloids were positively or negatively charged according to the nature of the polymer in excess. Dynamic light scattering (DLS) demonstrated that particles were formed at a very early stage in the complexation process. The consumption of the excess polyelectrolyte was monitored with a dye assay specific for dextran sulfate (toluidine blue) or chitosan (orange II). From these experiments, two different mechanisms of colloidal PEC formation were evidenced, according to the nature of the polymer in excess. On adding chitosan to DS in excess, regular consumption of the polyanion was observed at a constant stoichiometry, in the 1.5 to 1.85 range (sulfate residues for one glucosamine group), according to the molar mass of the polycation. When DS was added to chitosan in excess, the overall stoichiometry varied from ca. 6 (glucosamine residues for one sulfate group) down to 1 as the charge molar mixing ratio R=n+/n- decreased from 20 to 1. The existence of various mechanisms, according to the nature of the polymer in excess, could be attributed to the differences in chemical reactivity (strong vs low) of the ion in excess and the conformation and flexibility of the macromolecular chains related to their electrostatic potential.
Article: Polyelectrolyte Complex Nanoparticles of Poly (ethyleneimine) and Poly (acrylic acid): Preparation and Applications[show abstract] [hide abstract]
ABSTRACT: In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, media and structural parameters. Especially, mixing order, mixing ratio, PEL concentration, pH and molecular weight, were found to be sensible parameters to regulate the size (diameter) of spherical PEI/PAC nanoparticles, in the range between 80–1,000 nm, in a defined way. Finally, applications of dispersed PEI/PAC particles as additives for the paper making process, as well as for drug delivery, are outlined. PEI/PAC nanoparticles mixed directly on model cellulose film showed a higher adsorption level applying the mixing order 1. PAC 2. PEI compared to 1. PEI 2. PAC. Surface bound PEI/PAC nanoparticles were found to release a model drug compound and to stay immobilized due to the contact with the aqueous release medium.Polymers. 01/2011; 3:762-778.
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ABSTRACT: Growth factors are potent molecules that regulate cell functions including survival, self renewal, differentiation and proliferation. High-efficacy delivery of growth factors will be a powerful tool for regenerative medicine. Decades of intense research have significantly advanced the field of controlled delivery. There is, however, still a great unmet need for new methods that can improve overall efficacy of growth factor delivery. Here, we report a new growth factor delivery vehicle formed by self assembly of heparin and a biocompatible polycation, poly(ethylene argininylaspartate diglyceride) (PEAD). Of the many heparin-binding growth factors, we chose FGF-2 and NGF to demonstrate the potential of the [PEAD:heparin] delivery vehicle. The delivery vehicle incorporates both growth factors with high efficiency, controls their release, maintains the bioactivity of FGF-2 and increases the bioactivity of NGF relative to bolus delivery. [PEAD:heparin] appears to be a promising delivery matrix for many heparin-binding growth factors and may lead to efficient growth factor delivery for a variety of diseases and disabilities.Journal of Controlled Release 11/2010; 150(2):157-63. · 5.73 Impact Factor
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ABSTRACT: This contribution reviews polyelectrolyte (PEL) complex (PEC) nanoparticles prepared by mixing solutions of oppositely charged PELs, with special focus on the regulation of their size and shape by PEL structural and media parameters and on their pharmaceutical applications. Experimental and simulation evidence indicates that salt and PEL concentration, pH, mixing ratio and order, PEL molecular weight and topology are useful parameters for regulation of the size and internal structure of spherical PEC nanoparticles. Experimental and theoretical data are presented to show that PEL flexibility and stiffness are able to influence and even control PEC nanoparticle shape. Finally, the options, advantages, and challenges of dispersed PEC particles for pharmaceutical applications are outlined, emphasizing the uptake and release properties towards proteins and drugs and the interaction of these nanoparticles with cells.Advances in Polymer Science. 01/2012;