Portable two-color in vivo flow cytometer for real-time detection of fluorescently-labeled circulating cells

The recent introduction of the in vivo flow cytometer for real-time, noninvasive detection and quantification of cells circulating in the vasculature of small animals has provided a powerful tool for tracking the roles of different types of cells in disease progression. We describe a portable version of the device, which provides the capability to: a) excite and detect fluorescence at two distinct colors simultaneously, and b) perform data analysis in real time. These advances improve significantly the utility of the instrument and provide a means of increasing detection specificity. As examples, we present the depletion kinetics of circulating green fluorescent protein (GFP) labeled breast cancer cells in the vasculature of mice, and the specific detection of circulating hematopoietic stem cells labeled in vivo with two antibodies. (C) 2007 Society of Photo-Optical Instrumentation Engineers.