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The attraction between a negatively charged nanotube surface and a negatively charged osteoblast is facilitated by charged protein - mediators like proteins with a quadrupolar internal charge distribution , fibronectin and vitronectin .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None