7048
Polyethyleneimine ( PEI ) , a non - viral vector , has previously been optimised for high efficiency gene transfer in rat mesenchymal stem cells ( rMSCs ) .
 Chemical: Polyethyleneimine; Chemical: PEI
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: Polyethyleneimine; Chemical: PEI