30178
In this study , we describe a bio - inspired approach for preparing divalent ion - free alginate hydrogels that exhibit tunable physical and mechanical properties and improved biocompatibility due to the absence of cations in the gel matrices .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None