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Among these , cell - penetrating peptides ( CPPs ) , encompassing a family of short peptide sequences and their chimeric derivatives , have gained versatility through the addition of de novo peptide ligands primarily to facilitate cell - specific nucleic acid delivery in vitro and in vivo .
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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:
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