Summary of observations of nanoparticle-NIR dye distribution in tumors. Of the nanoparticles tested, NanoCy7.510k-PBA with chemically-conjugated Cy7.5 had highest signal-to-noise ratio (SNR), high signal in image-guided surgery, and had NIR signal distributed throughout the tumor in microscopy. NanoCy7.5100k-PBA had increased SNR compared to free Cy7.5-amine, but had low tumor-to-organ distribution, had less contrast during image-guided surgery because of high signal in background tissue, and low tumor penetration. Since NanoICGPBA had physically entrapped ICG, we assume the dye is being released from the NP before getting to the tumor. NanoICGPBA had low SNR values, but because of low background tissue signal, had large tumor-to-organ distribution values, had dim but tumor-specific signal in image-guided surgery, and had low tumor penetration of released ICG. Nanoparticles are not drawn to scale.