9957
Here , polyethylene glycol ( PEG ) and polyethylenimine ( PEI ) are covalently conjugated to GO via amide bonds , obtaining a physiologically stable dual - polymer - functionalized nano - GO conjugate ( NGO - PEG - PEI ) with ultra - small size .
 Chemical: polyethylene glycol; Chemical: PEG; Chemical: polyethylenimine; Chemical: PEI; Chemical: amide; Chemical: PEG; 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: polyethylene glycol; Chemical: PEG; Chemical: polyethylenimine; Chemical: PEI; Chemical: amide; Chemical: PEG; Chemical: PEI