Speciation diagrams as a useful tool to improve nanoparticle surface–ligand complexation for biocompatible magnetic colloids

Abstract

Biomedical applications of magnetic carriers are based on the specific interaction between the particle surface and ligands like meso-2,3-dimercaptosuccinic acid. Such cross-linking agents are polyfunctional Brönsted acids leading in aqueous media to several species the amounts of which vary strongly as a function of pH. Moreover, electrical double-layered magnetic colloids behave as a mixture of strong and weak diprotic acids and the analysis of the equilibria involved allows us to determine the quantitative pH dependence of the superficial density of the charge. Then, the behavior of coated magnetic nanoparticles by complexation of superficial metal ions should be controlled by the pH. In this context, we explore, from a theoretical point of view, the particle surface–ligand complexation in order to improve the synthesis of biocompatible magnetic fluids. The results obtained allow a theoretical prediction of the optimal pH for ligand–surface complexation and the colloidal stability in a physiological medium.

Acknowledgements: The authors thank the Brazilian agencies CAPES, CNPq and FAP-DF for their financial support.