25569
In order to circumvent the issues regarding systemic delivery and to increase the safety and efficacy of Ad therapies , the surface of oncolytic Ad was coated with cationic polymer chitosan via ionic crosslinking ( Ad / chitosan ) , after which polyethylene glycol ( PEG ) and / or folic acid ( FA ) was chemically conjugated onto the surface of Ad / chitosan , generating Ad / chitosan - FA , Ad / chitosan - PEG , and Ad / chitosan - PEG - FA nanocomplex .
 polyethylene glycol, PEG, folic acid, PEG, PEG - FA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polyethylene glycol, PEG, folic acid, PEG, PEG - FA