Self-assembly at nanometer length by amphiphilic moleculeswith solvent exposed hydrophobic groups are relevant in neurodegenerative disorders as well asin nano-bio technology. Here we study such self-assembly using a model system of spherical particles having charge at core but solvent repellingsurface,using Monte-Carlo simulations and mean field treatment. We findthat solvophobicity mediated attraction leads aggregation, while electrostatic repulsions control stability of finite clusters. The study qualitatively explains aggregation of misfolded proteins and can be useful guide to tune stability of nm sized self-assembly.