Fig. 3

Delivery of avidin-FITC to endothelial cells by biotin-conjugated peptides. Peptides selectively retained on brain endothelial cells were synthesized with biotin conjugated to their N-terminal. Their ability to increase avidin delivery to primary brain endothelial cells (a) and b.END3 cells (b) was assessed by incubating cells (1 h, 4 °C) with increasing concentrations of peptides followed by incubation (30 min, 4 °C) with avidin-FITC (50 µg/mL) (a, b). CFAG-biotin-mediated binding of avidin-FITC was similarly compared in primary brain and liver endothelial cells (c). The specificity of protein binding was assessed by measuring CFAG-mediated binding of avidin-FITC or albumin-FITC (both at equal molar concentrations) to b.END3 cells (d). Internalization rate of CFAG (50 μm) was compared in brain (b.End3) vs. liver EC (e) or primary brain EC vs. peripheral EC (f) by treatment with avidin-FITC following different time-periods of incubation (37 °C) after CFAG-biotin binding (e, dotted line indicates plateau of one-phase decay fitting). Results are displayed as mean ± SEM, of triplicate separate measurements from 3 (a, b, e) or 1 (c, d, f) independent experiments. Slope statistical significance vs. zero value (c)