Figure 1.

Multimodality Tracking Strategies of OVs

Expression of the EGFP reporter gene (EGFP) and red fluorescent protein reporter gene (RFP) in cytoplasm leads to the emission of fluorescent light (green light/red light). Transcription and translation of the firefly luciferase (FLUC) gene lead to cytosolic accumulation of the firefly luciferase enzyme, which subsequently catalyzes a photochemical reaction when d-luciferin is present. The resultant fluorescent light emission can be detected by imaging instruments. The human sodium iodide symporter (hNIS) gene may allow infected tumor cells to concentrate several free radionuclide probes such as ¹²³I, ¹²⁴I, ¹³¹I and 99^mTcO₄, which could facilitate viral imaging. Ferumoxytol-labeled neural stem cells loaded with OVs allow us to visualize the accumulation of the virus via MRI. In the same manner, magnetic nanoparticle (MNP)-assembled OV particles can be detected by MRI, enabling noninvasive viral monitoring.