In vivo bioluminescence imaging of implanted F3-effluc within hydrogel possessing different elasticities in nude mice. (a) A dual injection syringe containing 1 × 106 F3-effluc cells with HRP and H2O2 solution was used to produce a rapid gel reaction in in vivo environment. The bioluminescence images were acquired at different time points (0, 8, and 21 days) using an IVIS-100 imaging device (n = 3). Cell growth in the soft GPT 1.8 K was greater compared with both the cell-only and the stiff GPT 5.8 K groups. *P value <0.1 (b) In vivo kinetics of luciferase activity was conducted after d-luciferin administration in cell/hydrogel-injected nude mice. Bioluminescence signals were serially measured for 90 min at intervals of 5 min in the same mice. (c) The transparent hydrogel containing F3-effluc cells was resected from the thigh of mouse on day 0. The cell/hydrogel complex became pinkish with a large cell mass that proliferated within the complex on day 8. The initial time-to-peak on day 0 was different between the cell-only group and the soft and the stiff hydrogel groups. However, on day 8 and after, times-to-peak became similar for the three groups.