30182
Furthermore , alginate - catechol hydrogels enhanced the survival of various human primary cells including stem cells in the three - dimensional gel matrix , indicating that intrinsic cytotoxicity caused by divalent cations becomes negligible when employing catechol oxidation for alginate crosslinking .
 catechol, catechol
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 catechol, catechol