20181
To investigate the electrical charge ( modified by zero , one or two ammonium groups ) and the molecule length ( 3 , 5 or 7 methylene chains ) effects of bisphosphonate - type coatings , we assessed the complement activation , in vivo plasma and tissue relaxation time alterations of intravenously injected small iron oxide nanoparticles ( < 25nm ) on male healthy Wistar rats .
 Chemical: ammonium; Chemical: methylene; Chemical: bisphosphonate; 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: ammonium; Chemical: methylene; Chemical: bisphosphonate; Chemical: iron oxide