Design of cAlb biosensor for visualization of the molecular transport properties of thrombi generated in vivo. (A) BSA was labeled with cAlb, which is uncaged using 405-nm light to induce fluorescence. (B) Intravital microscopy was used to observe cAlb in vivo. Infusion of cAlb into the blood stream was followed by laser-induced injury to the mouse cremaster muscle arterioles to induce thrombus formation. Periodic pulses of 405-nm light were used to uncage cAlb and the resulting fluorescence intensity and decay were monitored with fluorescent microscopy. The represented fluorescence intensity has had the background subtracted and then been scaled to demonstrate signal decay within the thrombus. (C) Quantification of the intrathrombus cAlb signal was measured over multiple pulses of uncaging light for thrombus in panel B. (D) An average intrathrombus cAlb decay curve was generated by averaging the decay after each of 16 pulses taken over 3 minutes.