Immunofluorescent staining of macrophages (iNOS and CD163) surrounding 5 min- (A, C, E and G) and 16 hrs- (B, D, F and H) cured PEG-D4 hydrogels after 7 days of subcutaneous implantation. Cell nuclei, macrophage type 1 (M1), and macrophage type 2 (M2) were stained by DAPI (blue), iNOS (green), and CD163 (red), respectively. The letter h indicates the location of the implanted hydrogel. The dash line indicates the interface between the hydrogel and the surrounding tissue. Scale bar: 100 μm.