3366
To afford the user additional control over the presentation of microtopographic cues to cell populations , a photolabile , PEG - based hydrogel system is presented in which precisely engineered topographic cues can be formed in situ by controlled erosion .
 Chemical: PEG
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: PEG