Fig. 3

In vitro evaluation of the immunomodulatory properties of the piezoelectric hydrogels. a Schematic diagram of immune regulation by the piezoelectric hydrogels. b Evaluation of the cytocompatibility of the piezoelectric hydrogels. c–d 2D and 3D live and dead cell staining of macrophages (RAW 264.7 cells) cocultured with the piezoelectric hydrogels. Scale bar: 200 μm (c), 100 μm (d). e Representative immunofluorescence images of RAW 264.7 cells on hydrogels. F-actin (green) is a fibrous actin that presents the skeleton of the cells, F4/80 (red) is cell surface glycoprotein and the marker of mature mouse macrophages, DAPI (blue) stands for the nucleus. Scale bar: 25 μm. f Representative flow cytometric dot plots showing cell surface markers of RAW 264.7 cells, including CD86 and CD206. g Representative immunofluorescence images of iNOS (red) and CD206 (green) in RAW 264.7 cells on hydrogels on day 2. Scale bar: 25 μm. h Relative mRNA expression levels of anti-inflammatory genes and pro-inflammatory genes of macrophage under the piezoelectric hydrogels stimulation for 2 d. ^*P < 0.05, compared with the control group; ^#P < 0.05, compared with the CG group; ^$P < 0.05, compared with the CG/PHA group; ^@P < 0.05, compared with the CG/PHA/5%PBT group. CG chitosan/gelatin, PHA polydopamine coated-hydroxyapatite, PBT polydopamine coated-barium titanate, IL-6 interleukin-6, TNF-α tumor necrosis factor-α, iNOS inducible nitric-oxide synthase, IL-4 interleukin-4, IL-10 interleukin-10, Arg1 arginase 1