Fig. 2.
Optical imaging for in vivo immune cell tracking. (A) Fluorescence comprises the excitation of a fluorescent molecule, causing its electrons to move to a higher energy state, then return to a ground state, releasing the energy as light. This light is imaged with FLI.64 (B) Bioluminescence occurs when a luciferase enzyme catalyzes the reaction of a luciferin with oxygen, ATP, and cofactors to produce light that can be measured with BLI.64 Copyright © The Author(s). Cancer Medicine published by John Wiley & Sons Ltd. (C) Bioluminescence imaging of a tumor expressing luciferase. In the control, the tumor continued growing over 7 days, causing the signal to spread and become brighter. In mice treated with NK cells, the signal decreases as the tumor shrank from the treatment.65 Copyright © 2017 Zhu, Li, Kalimuthu, Gangadaran, Lee, Oh, Baek, Jeong, Lee, Lee and Ahn. (D) Fluorescence imaging to observe nitric oxide produced by macrophages treated with different immunotherapy drugs responding to a tumor in a mouse model.90 Copyright © The Author(s). Advanced Materials published by John Wiley & Sons Ltd. (E) Mice were injected with DiR labeled T cells one week prior to introducing 4T1, a murine breast cancer cell line, then monitored with fluorescence imaging after 4T1 injection. T cells migrated to the tumor within 2 hours and the signal remained mostly stable for at least 2 weeks.67