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Biodegradable oligo ( poly ( ethylene glycol ) fumarate ) ( OPF ) composite hydrogels have been investigated for the delivery of growth factors ( GFs ) with the aid of gelatin microparticles ( GMPs ) and stem cell populations for osteochondral tissue regeneration .
 Chemical: oligo ( poly ( ethylene glycol ) fumarate ); Chemical: OPF
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: oligo ( poly ( ethylene glycol ) fumarate ); Chemical: OPF