Balb/C mice were injected intravenously through the retro-orbital vein with mRPZ, mRNA-PEI utilizing an N/P ratio of 9.3 (PEI N/P=9.3), in vivo JetRNA+ (JetRNA) a commercial lipid reagent, or PBS. The expression of luciferase was monitored over 96 hours by injecting mice in their intraperitoneal cavity with a luciferin DPBS solution and measuring the luminescence with an IVIS live imaging system. The images taken were analyzed using IVIS software and the mean radiance was collected measuring the entire body of each mouse. The kinetics of luciferase expression were tracked using the image data over 96 hours (Figure ). mRPZ shows the same clear delayed maximum expression of mRNA in vivo as it does in vitro when compared to a commercial lipid reagent. mRPZ reaches a maximum expression between 12 to 18 hours post-injection, while JetRNA reaches a maximum of 3 hours post-injection, both gradually taper off over 96 hours. PEI N/P=9.3 showed some expression in vivo but not statically above background (PBS), even when controlling for sex (Figure ).