7954
Cultures of primary hepatocytes became already an inherent part of the preclinical pharmaco - toxicological testing battery , yet their routine use , particularly for long - term assays , is limited by the progressive deterioration of liver - specific features .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None