Figure 4.

A comparison of in vivo stability of encapsulated vs. unmodified QD-BRET conjugates. The two types of conjugates were injected subcutaneously into the same animal (left: encapsulated; right: unmodified) and monitored for QD fluorescence (a) and bioluminescence (b). QD fluorescence images were taken under excitation with 465 nm, and bioluminescence and BRET images were taken immediately after injection of coelenterazine. Open filter collects light signals across the whole spectrum, and QD filter only collects light emitting between 650–660nm. Bottom graphs (c) show bioluminescence signals and BRET ratios changes over time; note that BRET ratios are smaller than in vitro measurement, because the BRET signals were only collected over 650–660 nm, instead of 600–750 nm as in vitro.