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Their advantages in the fields of magnetic drug targeting and imaging are well established and their safety is assumed , since iron oxide nanoparticles have already been approved for in vivo application , however , according to many literature reports the bare metal oxide nanoparticles may cause toxic effects on treated cells .
 Chemical: iron oxide
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: iron oxide