Effect of Polyelectrolyte Structure on Protein−Polyelectrolyte Coacervates:  Coacervates of Bovine Serum Albumin with Poly(diallyldimethylammonium chloride) versus Chitosan

Abstract

Electrostatic interactions between synthetic polyelectrolytes and proteins can lead to the formation of dense, macroion-rich liquid phases, with equilibrium microheterogeneities on length scales up to hundreds of nanometers. The effects of pH and ionic strength on the rheological and optical properties of these coacervates indicate microstructures sensitive to protein-polyelectrolyte interactions. We report here on the properties of coacervates obtained for bovine serum albumin (BSA) with the biopolyelectrolyte chitosan and find remarkable differences relative to coacervates obtained for BSA with poly(diallyldimethylammonium chloride) (PDADMAC). Coacervation with chitosan occurs more readily than with PDADMAC. Viscosities of coacervates obtained with chitosan are more than an order of magnitude larger and, unlike those with PDADMAC, show temperature and shear rate dependence. For the coacervates with chitosan, a fast relaxation time in dynamic light scattering, attributable to relatively unrestricted protein diffusion in both systems, is diminished in intensity by a factor of 3-4, and the consequent dominance by slow modes is accompanied by a more heterogeneous array of slow apparent diffusivities. In place of a small-angle neutron scattering Guinier region in the vicinity of 0.004 Å -1 , a 10-fold increase in scattering intensity is observed at lower q. Taken together, these results confirm the presence of dense domains on length scales of hundreds of nanometers to micrometers, which in coacervates prepared with chitosan are less solidlike, more interconnected, and occupy a larger volume fraction. The differences in properties are thus correlated with differences in mesophase structure.

Bipolar tetraether lipids derived from thermoacidophilic archaeon Sulfolobus acidocaldarius for membrane stabilization of chlorin e6 based liposomes for photodynamic therapy

“…This highlights the potential of DOTAP based complex to facilitate loading of Ce6 through its ability to interact with the lipid. These observations are in agreement with previous studies which showed that the coacervate yield was considered to be maximal at 1:1 charge stoichiometry (''[À]:[+])'' [38,39]. Subsequently, formulations based on two DOTAP:Ce6 molar ratios at 6 (FI) and 9 (FII) were selected to prepare TELs-liposomes.…”

Cationic polyelectrolytes–lipases complexes formation as tool for recovery of these enzymes from their natural sources

“…From the point of view of the downstream processes, it is highly desirable for the simplicity of the unit operation and economy cost of it. When the titration curves were carried out in presence of high NaCl concentration, no turbidity formation was observed, similar results have been found for the interaction of other protein-polyelectrolytes [11]. The data obtained fully confirm the assumption of the presence of an electrostatic component part; coulombic forces involved in the PEI-lipases complex formation, however, the increase of ionic strength did not produce the total inhibition of the PEI lipase complex formation a total cancellation of the polymer-protein interaction, suggesting the par- Experimental data were fitted in a non-linear way and presented in Fig.…”

“…Both lipases were recovered from the precipitate by adding salt to the medium, confirming the net electrostatic character of the complex formation. The polyelectrolytes concentrations required to precipitate both enzymes were very low in comparison to other methods using salt or organic solvents [11]. In the case of PPL, concentrations not exceeding 0.08 mg PEI/mg of lipase were necessary, while the same enzyme was precipitated by CHS at concentrations ten times lower.…”

The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes

“…Electrostatically-driven self assembly can be tuned through a variety of parameters, including the chemical nature of the charged species, the size or length of the charged particle or molecule, particle shape, polydispersity, charge density, pH, and ionic strength [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Consideration of these variables is critical in the design of self-assembled materials.…”