The cell culture medium and hydrogel matrix include an effective amount of polar amino acids, the polar amino acids selected from {HEAD ~ the group} consisting of arginine, {TAIL ~ lysine}, histidine, glutamic acid, and aspartic acid 
consisting of
The cell culture medium and hydrogel matrix include an effective amount of polar amino acids , the polar amino acids selected from { HEAD ~ the group } consisting of arginine , { TAIL ~ lysine } , histidine , glutamic acid , and aspartic acid
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH