Dendrimer-Stabilized Titanate Nanowire Dispersions as Potential Nanocarriers
The effect of poly(amido amine) (PAMAM) dendrimers of generations G2, G6, and G10 on the dispersion stability of titanate nanowires (TiONWs) as potential nanocarriers was clarified in order to develop biocompatible delivery systems. The PAMAMs adsorbed strongly on the oppositely charged TiONWs even under slightly alkaline conditions where the macromolecules possess low amounts of charged groups and they were able to reverse the charge of the particles. This process resulted in unstable dispersions near the dose where the charge reversal occurred, while stable samples were observed away from it. No generation dependence was found on the aggregation and charging behavior at low ionic strengths. Although heterogeneous adsorption of the dendrimers led to attractive patch-charge interactions at intermediate doses, interparticle forces of electrostatic origin described by Derjaguin and Landau, Verwey, and Overbeek (DLVO) played the major role in colloidal stability. The nanowires were found to adopt a face-to-face orientation within the aggregates, giving rise to the formation of well-defined bundles. Highly stable dispersions were observed once the TiONWs were coated with PAMAM dendrimers of higher generations even at elevated ionic strengths.