In a separate study, the researchers coated SPIONs with biocompatible, biodegradable coatings of chitosan, PEG, and PEI to achieve the targeted delivery of anti−Ape1 siRNA to pediatric brain tumor cells, reducing Ape1 expression by more than 75% and Ape1 activity by 80% in medulloblastoma and ependymoma cells [110]. The gene discussed is APEX1; the disease is medulloblastoma.