The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes

Abstract

Abstract:The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(L-lysine) (PLL) molar mass on the interaction with statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been systematically investigated for different PAMAMPS chemical charge densities (15% and 100%) and different ionic strengths. The study of the ionic strength dependence of the binding constant allowed the determination of the total number of released counter-ions during the formation of the PEC, which can be compared to the total number of counter-ions initially condensed on the individual polyelectrolyte partners before the association. Interestingly, this fraction of released counter-ions, which was strongly dependent on the PLL molar mass, was almost independent of the PAMAMPS charge density. These findings are useful to predict the binding constant according to the molar mass and charge density of the polyelectrolyte partners.

Amphiphilic PLGA‐PEG‐PLGA triblock copolymer nanogels varying in gelation temperature and modulus for the extended and controlled release of hyaluronic acid

“…These complexes, once neutralized, can take different conformations such as ladder‐like structures (fibril/networks) or entanglements . Based on our observations, the release of HA is slowed with shorter PLL chains due to counterion‐mediated overlap of oppositely charged chains [Figure (d)] . Neutralized chains can form more compact complexes.…”

“…In addition, the presence of salt ions further weakens the electrostatic interactions as the creation of loops reduces the amount of released counterions [Figure (c)]. Semi‐neutralized chains form more hydrated complexes causing the hydrogels to become more swollen (data not shown) and lowering the polymer volume fraction. As a consequence of lower polymer volume fraction, the release of HA can be accelerated.…”

“…75 Based on our observations, the release of HA is slowed with shorter PLL chains due to counterion-mediated overlap of oppositely charged chains [ Figure 5(d)]. 73,74 Neutralized chains can form more compact complexes. Based on their overall hydrophilicity or hydrophobicity they can either interact with the PLGA micelle core or allow the micelles to embed among the PECs.…”

Effect of Dendrigraft Generation on the Interaction between Anionic Polyelectrolytes and Dendrigraft Poly(l-Lysine)

“…The number of counter-ions that are effectively released from the association of n ligands onto one PAMAMPS chain can be determined by calculating −∂<n>logk∂logI [41,42,43]. These numerical values are reported in Table 2 and Table 3 for PAMAMPS 30% and 100% respectively, and are compared to the one obtained for linear PLL50-PAMAMPS interactions (see Figure 6).…”

“…To examine the effect of dendrimer generation on the thermodynamic binding parameters, isotherms of adsorption were plotted for three successive generations of DGL (G2, G3, and G4) in interaction with linear polyanions of different charge densities (PAMAMPS 30% and PAMAMPS 100%). In this work, we have used a PAMAMPS 30% (instead of 15% in our former publication about PLL/PAMAMPS interactions [ 41 ]) because DGL/PAMAMPS 15% mixtures required very long equilibrium times (more than 24 h), while in the case of the PDGL/PAMAMPS 30% the equilibrium was reached in less than 12 h. For that purpose, FACCE methodology developed by Sisavath et al [ 34 ] was used. In this method, a continuous voltage and a co -pressure were simultaneously applied in order to introduce selectively the free ligand (free DGL) in the capillary, avoiding the dynamic dissociation of the complex during electrophoretic migration.…”