Silica nanoparticles are attractive carriers for drug delivery due to their improved safety and effectiveness in drug delivery. Silica nanoparticles were synthesized by using microemulsion assisted sol-gel method. Silica nanoparticles were synthesized by using microemulsion assisted sol-gel method and a model anticancer drug 5-fluorouracil (5-FU) was added to the silica precursor before hydrolysis and condensation reactions start. The obtained materials were characterized by means of Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). The drug encapsulation within silica nanoparticles causes a particle size increase. However, the particle morphology is not affected. The drug release profile was obtained through high performance liquid chromatography (HPLC). The encapsulation approach showed to be effective to sustain a continuous and increasing release during the testing time (98 hours). Further studies were performed to evaluate the cytotoxic effects of silica nanoparticles with loaded 5-FU on Chinese hamster ovary (CHO- K1) cells. The materials are non-cytotoxic for all concentration tested (5-200 µg/mL).