Dynamic light scattering and zeta potential of colloidal mixtures of amelogenin and hydroxyapatite in calcium and phosphate rich ionic milieus

Abstract

The concept of zeta-potential has been used for more than a century as a basic parameter in controlling the stability of colloidal suspensions, irrespective of the nature of their particulate ingredients – organic or inorganic. There are prospects that self-assembly of peptide species and the protein-mineral interactions related to biomineralization may be controlled using this fundamental physicochemical parameter. In this study, we have analyzed the particle size and zeta-potential of the full-length recombinant human amelogenin (rH174), the main protein of the developing enamel matrix, in the presence of calcium and phosphate ions and hydroxyapatite (HAP) particles. As calcium and phosphate salts are introduced to rH174 sols in increments, zeta-potential of the rH174 nanospheres is more affected by negatively charged ions, suggesting their tendency to locate within the double charge layer. Phosphate ions have a more pronounced effect on both the zeta-potential and aggregation propensity of rH174 nanospheres compared to calcium ions. The isoelectric point of amelogenin was independent on the ionic strength of the solution and the concentration of calcium and/or phosphate ions. Whereas rH174 shows a higher affinity for phosphate than for calcium, HAP attracts both of these ions to the shear plane of the double layer. The parallel size and zeta-potential analysis of HAP and rH174 colloidal mixtures indicated that at pH 7.4, despite both HAP and rH174 particles being negatively charged, rH174 adsorbs well onto HAP particles. The process is slower at pH 7.4 than at pH 4.5 when the HAP surface is negatively charged and the rH174 nanosphere carries an overall positive charge. The results presented hereby demonstrate that electrostatic interactions can affect the kinetics of the adsorption of rH174 onto HAP.

Liposomes in tissue engineering and regenerative medicine

“…The zeta (z)-potential is used to measure the intensity of the repulsive electrostatic interaction between naturally charged colloidal particles [73]. Indeed, measurements of zeta potential are commonly used to predict the stability of colloidal systems.…”

Stabilization of Weakly Charged Microparticles Using Highly Charged Nanoparticles

“…They are used in inks, paints, and other emulsions, pharmaceutical products, and are found naturally in clays, biological fluids such as blood, natural organic matter colloids, and petroleum and geological processes. The stability of colloidal particles during transport through porous media is important in separation processes and the spread of contaminants, nutrients, and bio-solids through soil [1][2][3][4][5][6][7][8][9][10]. In all applications it is necessary to be able to maintain the colloid in a dispersed with the particles suspended as individual particles and with minimal amounts of flocculation.…”

Calcium phosphate substrates with emulsion-derived roughness: Processing, characterisation and interaction with human mesenchymal stem cells

“…2E) [53]. This is justified by the complex surface charges of HA, which may vary with the preparation method [54].…”