13727
In this study , primary vascular endothelial cells were treated with TiO2 NPs for 2 - 16h at concentrations of 0 - 50 mu g / mL .
 Chemical: TiO2
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: TiO2