Figure 2.

Representative hydrogel matrices in engineered living hydrogels. a-c) Living microbial cells dispersed in cell-generated hydrogels. Examples include an E. coli-produced curli fibril biofilm used as an electrical switch (b) and an E. coli-generated curli hydrogel used as a mucoadhesive patch in the gut (c). (b) Reproduced with permission^[41]. Copyright 2014, Springer Nature. (c) Reproduced with permission^[42]. Copyright 2019, Wiley-VCH. d-f) Living microbial cells dispersed in synthetic hydrogels. Examples include microbial cell-laden hydrogel beads used as a heavy-metal detector in the environment (e) and a 3D-printed, cell-laden hydrogel pattern used as a biosensor on the skin (f). (e) Reproduced with permission^[24]. Copyright 2021, Springer Nature. (f) Reproduced with permission^[22]. Copyright 2018, Wiley-VCH. g-i) Living microbial cells enclosed in hydrogel chambers. Examples include a stretchable hydrogel-elastomer hybrid containing microbial cells in channels (h) and a 3D-printed, core-shell hydrogel structure containing microbial cells in cavities (i). (h) Reproduced with permission^[46]. Copyright 2017, National Academy of Sciences. (i) Reproduced with permission^[53]. Copyright 2013, National Academy of Sciences.