The use of nanotechnology in drug delivery is a rapidly expanding field. Biodegradable or nontoxic nanomaterials have the most promising application potentials in nanomedicine. Herein, we report a novel core-shell nanoparticle with double shell coatings (silica and poly(D,L-lactide-co-glycolide) (PLGA)) with the total shell thickness of (8.7 ± 1.3) nm. The outer shell of PLGA is biodegradable and used for controlled and sustained release, and the inner shell of silica is mesoporous for the preservation of the chemical radiation therapeutic of methyl viologen (MV), an oxidant that produces reactive oxygen species during cancer radiation therapy. The dissolution time course data and transmission electron microscopy images showed that the novel nanoparticles (Au@SiO2&PLGA) have been successfully prepared, and silica and PLGA coated well the gold (Au) template surfaces. Nano- capsules (MV@SiO2&PLGA) were obtained after the gold templates were dissolved using sodium cyanide. The sustained release property was characterized through detecting fluorescence quenching time course of fluorescent isothiocyanate after mixing with MV@SiO2&PLGA nanocapsules that encapsulate MV molecules. The sustained release of MV molecules could be extended to approximately four weeks. This novel delivery system has high potential in future application for the delivery of therapeutic drugs, particularly for the treatment of cancer by radiation therapy. The use of nanotechnology in drug delivery is a rapidly expanding field. Biodegradable or nontoxic nanomaterials have the most promising application potentials in nanomedicine. Herein, we report a novel core-shell nanoparticle with double shell coatings (silica and poly (D, L-lactide -co-glycolide (PLGA)) with the total shell thickness of (8.7 ± 1.3) nm. The outer shell of PLGA is biodegradable and used for controlled and sustained release, and the inner shell of silica is mesoporous for the preservation of the chemical radiation therapeutic of methyl viologen (MV), an oxidant that produces reactive oxygen species during cancer radiation therapy. The dissolution time course data and transmission electron microscopy images showed that the novel nanoparticles (Au @ SiO2 & PLGA) have been successfully prepared, and silica and PLGA coated well the gold (Au) template surfaces. Nano- capsules (MV @ SiO2 & PLGA) were obtained after the gold templates were dissolved using sodium cyanide. release property was characterized through 2 fluorescence isothiocyanate after mixing with MV @ SiO2 & PLGA nanocapsules that encapsulate MV molecules. The sustained release of MV molecules could be extended to about four weeks. This novel delivery system has high potential in future application for the delivery of therapeutic drugs, particularly for the treatment of cancer by radiation therapy.