9482
The transfection efficiency of a model gene ( luciferase ) in MCF7 and HEK293 cell lines increased with increasing x ( RPLL content ) in the PRL ( x ) polyplexes until peaking at x = 2 . 5 and 10 , respectively , after which point transfection efficiency declined rapidly .
 polyplexes
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polyplexes