Fig. 2

Overview of the NIR-FCS experiments and data analysis in flowing blood. a Monitoring NIR fluorescent species in flowing blood. Blood containing CB1 (8 nM) was pumped through a flow channel at a defined velocity of 50 µL h⁻¹. The FCS observation volume was consequently either free (schematics 1) or occupied (schematics 2) by a blood cell. Correspondingly, the fluorescence intensity time trace revealed high (1) and low (2) intensity time segments. b The experimental autocorrelation curve (squares) was fitted (line) with analytical model, Eq. (3), combining standard and inverse FCS thus taking into account contributions of fluorescent species and blood cells, respectively. c The information extracted from the fit in panel (c) was used to subtract the cells’ contribution and obtain an autocorrelation curve (squares) resembling that of a standard FCS experiment (Eq. ( 6)). A fit with Eq. (1) (line) yields diffusion properties of the fluorescent species