Förster resonance energy transfer (FRET) and aggregation-caused quenching (ACQ) are well-established mechanisms with promising potential to eliminate interference from free probes in studies of in vivo nanocarrier behavior. However, both approaches have a critical limitation, fluorescence reillumination. This problem arises when aggregates of quenched ACQ probe redisperse, or separated FRET probe pairs recouple, after repartitioning and enrichment in hydrophobic domains, leading to significant interference. To minimize reillumination, our study employs an “And” logic-gate strategy, integrating ACQ and FRET principles. We screened a series of near-infrared (NIR) fluorophores based on the BODIPY parent structures to identify an optimized ACQ-FRET dual-functional probe pair, where BDP1 was chosen as the donor and P1 as the acceptor. Compared to the individual donor (BDP1) or acceptor (P1), the ACQ-FRET probe pair dramatically reduced reillumination-derived interference in both plasma and cell line assays. Subsequent in vivo and ex vivo bioimaging confirmed the superior performance of the ACQ-FRET probe, which consistently exhibited the lowest reillumination interference (below 15%) among all tested probes. This performance significantly outperformed that of BDP1 (32%) and P1 (47%), and even exceeded P2 (19%), a well-established NIR probe characterized by relatively low reillumination.
Liu et al. (Sun,) studied this question.