2287
Crosslinked polyethylenimines ( PEIs ) have been frequently examined over the past decade since they can maintain the transfection efficiency of commercially available , 25k branched PEI , but exhibit less cytotoxicity .
 Chemical: polyethylenimines; Chemical: PEIs; Chemical: PEI
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: polyethylenimines, PEIs, PEI 
Answer:
 Chemical: polyethylenimines; Chemical: PEIs; Chemical: PEI