18965
A versatile chemical scheme is used to modify the reactive PEG microgels with tethered biomolecules to tune their bioactive properties for the bioreactor culture and manipulation of various ( stem ) cell types .
 PEG
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PEG