7484
In this review , various approaches for the design and preparation of PVP - modified surfaces are summarized and potential biomedical applications of these PVP - modified materials are indicated .
 PVP, PVP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PVP, PVP