Fig. 4: Modification of secretory light-responsive engineered bacteria.

a The emission spectra of blue light emitted UCRs. b The principle of PEGDA-co-SMAS hydrogel cross-linking. c The scheme of PEGDA-co-SMAS hydrogel preparation. d The morphology of UCRs-doped microspheres. e Fourier-transform infrared spectroscopy (FITR) spectrum of PEGDA hydrogels grafted with SMAS of different contents. f The zeta potential of PEGDA hydrogels grafted with SMAS of different contents (n = 3). g The images of PEGDA-co-SMAS hydrogel microspheres containing ICG, which were immersed in artificial simulated gastric fluid SGF (pH 1.2) and artificial simulated intestinal fluid SIF (pH 6.8 and 7.4) for 3 h. h UV-visible spectrophotometric analysis of released ICG in different pH buffers. i The quantitative detection of released ICG. j Cell viability of different doping ratios of ICG and PEGDA hydrogel (n = 5). k Analysis of in vivo retention time of PEGDA-co-SMAS hydrogel microspheres containing ICG in different intestinal segments. l Mean fluorescence intensity of ICG in different intestinal segments. m)GFP expression (n = 5). Data are expressed as the mean ± SEM; *P < 0.05, **P < 0.01, ***P < 0.001.