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Hydrogel biomaterials based on poly ( vinyl alcohol ) , PVA , have an extensive history of biomedical applications , yet in their current form suffer from significant shortcomings , such as a lack of mechanism of biodegradation and poor opportunities in controlled drug release .
 Chemical: poly ( vinyl alcohol ); Chemical: PVA
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: poly ( vinyl alcohol ); Chemical: PVA