Water-in-oil (W/O)emulsions using crop oils and stabilized by surface modified silica nanoparticles and polymeric surfactants appear to be a promising approach for storing and delivering microorganisms to aqueous environments. In these systems cells are contained within the internal phase of the emulsion. We examined two types of silica nanoparticles for stabilizing Chlorella vulgaris in W/O emulsions and release kinetics upon delivery to water. C vulgaris was selected because of its potential for nutritional and industrial applications. We also examined the effects of silica nanoparticles on the release of a model solute NaCl. Surface modification of the nanoparticles and concentration of nanoparticles in the continuous phase had significant effects on the release of NaCl while only surface modification had an effect on the release of cells. Increasing the hydrophobicity of the nanoparticles significantly reduced the level of cell release and rate of solute release suggesting emulsion properties could be tailored to achieve the controlled release of cells and solute upon delivery. (C) 2009 Elsevier Ltd. All rights reserved.