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The double - layered wound dressing was developed with PVA / sodium alginate using a freeze - melting technique ; one layer was PVA layer and the other was the drug - loaded sodium alginate layer .
 Chemical: PVA; Chemical: sodium alginate; Chemical: PVA; Chemical: sodium alginate
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: PVA; Chemical: sodium alginate; Chemical: PVA; Chemical: sodium alginate