The colloidal stability of fluorescent calcium phosphosilicate nanoparticles: The effects of evaporation and redispersion on particle size distribution

Understanding the colloidal stability of nanoparticles is important for biological applications, such as bio-imaging and drug delivery. This work combines theoretical calculations with experimental data to elucidate the mechanism of stabilization for calcium phosphosilicate nanoparticles containing Cy3 with both citrate and poly(ethylene glycol) (PEG) surface conjugation. The citrate surface is shown to provide electrosteric dispersion in water-ethanol mixtures as well as the ability to redisperse after evaporating the solvent. Improved colloidal stability is afforded with the addition of PEG with respect to redispersion after drying. Changes in average agglomeration number (AAN) are tracked and explained by DLVO and the Napper electrosteric and steric theories for dispersion, respectively.