8463
We addressed the issue by comparing the in vitro antiprion ability of numerous modified poly ( propylene - imine ) dendrimers , which varied in size , structure , charge , and surface group composition .
 poly ( propylene - imine )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 poly ( propylene - imine )