Stöber method has been used for the formation of NP@SiO2 core-shell particles in this study. Using a molecule served as the primer for the surface activation, tetraothorsilance (TEOS) was deposited onto the surfaces of serval different types of nanoparticles. The thickness and morphology of silica shell were adjusted by changing the amounts of silica precursor, and ammonium hydroxide which was used as catalyst for the hydrolysis of TEOS with the addition of ethanol and water. The core of the core-shell nanoparticles can be removed by reacting with hydrochloric acid. By controlling the reaction time and concentration of HCl, yolk-shell structure was generated. The reaction kinetics can be followed by in-site UV-vis absorption. The core-shell and hollow particles can be loaded with antibiotic in deionized water and used for the inhibition of Streptococcus. mutant bacteria. The formation and drug-loading capacity of various types of nanoparticles will be presented in this talk.