19807
The serum competitive study showed that the highly PEG - grafted PLL is better for preventing serum binding to the Photofrin / PLL - g - PEG complex .
 Chemical: PEG - grafted PLL; Chemical: Photofrin; Chemical: PLL - g - PEG
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: PEG - grafted PLL; Chemical: Photofrin; Chemical: PLL - g - PEG