Fig. 2: Characterization of cytokine production kinetics mediated by FLICs-loaded hydrogel implants.

a Schematic of the experimental procedure for preparation of FLICs-loaded hydrogel implants. FLICs (2.5 × 10⁶) in 60 µL Dulbecco’s Modified Eagle Medium were mixed with 240 µL polysaccharide-based biocompatible hydrogel solution. Hydrogel matrix is crosslinked by ions (such as Ca²⁺ or Na⁺) interactions from the cell culture medium and then solidified in a 48-well plate. b Photograph showing a representative FLICs-loaded hydrogel implant. c–e Illumination-intensity-dependent cytokines (IFN-β, TNF-α, and IL-12) release kinetics of the FLICs-loaded hydrogel implants. FLIC (2.5 × 10⁶)-loaded hydrogel implants were illuminated with FRL at different light intensities (0, 0.2, 1, 5 mW/cm²) for 4 h once a day for 2 days, and culture supernatants were collected to quantify (c) IFN-β, (d) TNF-α, and (e) IL-12 production using corresponding enzyme-linked immunosorbent assay (ELISA) kits 48 h after the first illumination. f–h Exposure-time-dependent cytokines (IFN-β, TNF-α, and IL-12) release kinetics of the FLICs-loaded hydrogel implants. FLIC (2.5 × 10⁶)-loaded hydrogel implants were illuminated with FRL (1 mW/cm²; 730 nm) for 0, 2, 4, 6 h once a day for 2 days, culture supernatants were collected to quantify (f) IFN-β, (g) TNF-α and (h) IL-12 production using corresponding ELISA kits 48 h after the first illumination. i–k Reversibility of cytokines (IFN-β, TNF-α, and IL-12) release mediated by the FLICs-loaded hydrogel implants. FLICs-loaded hydrogel implants were either illuminated with FRL (1 mW/cm²) for 20 min (ON) or instead kept in the dark (OFF), and cytokines (i) IFN-β, (j) TNF-α, and (k) IL-12 production was scored every 6 h for 72 h. At the beginning of each 24-h cycle, the culture medium was replaced with fresh medium. Data in c to k are presented as the mean ± SD; n = 3 independent experiments. Source data are provided as a Source Data file.