Figure 3.

Genetically engineered HEK-293 cells that express luciferase in response to VEGF were exposed to various treatments. HEK-293 cells treated with media or buffer exhibit low luminescence, while cells exposed to recombinant VEGF display a concentration-dependent luminescence (gray bars). HEK-293 cells treated with the supernatants of buffer-loaded RBCs (white bars) which are Unlysed or glass-bead Lysed RBCs induce negligible luminescence, consistent with the absence of VEGF in the media. Similar nominal luminescence was observed for HEK-293 cells that had been treated with the supernatant of Unlysed VEGF-loaded RBCs (black bar). By contrast, glass bead Lysed VEGF-loaded RBCs (black bar) induce a significant luminescent response in HEK-293 cells. Finally, we examined the impact of RBCs surface modified with the phototrigger containing either buffer (white bars) or VEGF (black bars). In the Dark, the buffer-loaded RBCs (white bars) do not produce a VEGF-dependent luminescent response. The corresponding response in the Dark from the VEGF-loaded RBCs is slightly above background (similar to that observed with Unlysed VEGF-loaded RBCs) and may be a consequence of the presence of residual unloaded VEGF in solution. By contrast, exposure of RBCs containing VEGF to Light triggers a robust luminescence, which is approximately 80-fold greater than that observed with RBCs in the dark.