20040
We summarize common synthetic approaches to these materials , and then survey the most recent imaging applications of silica - based nanoparticles in cancer .
 Chemical: silica
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: silica 
Answer:
 Chemical: silica