Listening to reporter proteins: how loud does the message need to be?

Abstract

Optical imaging as non-invasive modality has tremendous research applications in the area of biomedical sciences such as characterization of cancerous cells. However, this imaging modality is limited by depth of light penetration of around 1 mm in living tissues obscuring visualization in vivo. Optoacoustic imaging is a potential solution of this problem based on detection of ultrasound produced by light-absorbing molecules exposed to laser radiation resulting in a tissue contrast. The image contrast relies on absorption of laser emission, however providing ultrasound resolution in living tissues. This study characterized properties of colorectal adenocarcinoma cells expressing Near-infrared Fluorescent proteins (iRFPs) for detection and visualization in Multispectral Optoacoustic Tomography (MSOT) settings in both tissue-mimicking phantoms and mice. We estimated variables affecting MSOT imaging of 3D multicellular tissue spheroids such as size, expression of iRFP in vitro. We tested MSOT for detection of subcutaneously implanted tumours expressing iRFPs in BALB/C nude mice in vivo.