A nanotherapeutic having platinum complexes encapsulated by a nanoformulation containing at least one spinel ferrite of formula CuFe2O4, NiFe2O4, CoFe2O4, and MnFe2O4 deposited on mesoporous silica. A method of preparing the nanotherapeutic that involves mixing a metal(II) salt and a Fe(III) salt with the mesoporous silica nanoparticles to form a powdery mixture, calcining the powdery mixture to form the nanoformulation, and mixing the nanoformulation with the platinum complex. A method for treating cancer with the nanotherapeutic.