25575
Although tissue - penetrable light ( red and NIR ) has a great potential for spatiotemporally controlled release of therapeutic agents , it has been hampered because of the lack of chemistry translating the photonic energy to a cleavage of a chemical bond .
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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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