A mechanism to signal receptor-substrate interactions with luminescent quantum dots.

Semiconductor quantum dots are becoming valuable analytical tools for biomedical applications. Indeed, their unique photophysical properties offer the opportunity to design luminescent probes for imaging and sensing with unprecedented performance. In this context, we have identified operating principles to transduce the supramolecular association of complementary receptor-substrate pairs into an enhancement in the luminescence of sensitive quantum dots. Our mechanism is based on the electrostatic adsorption of cationic quenchers on the surface of anionic quantum dots. The adsorbed quenchers suppress efficiently the emission character of the associated nanoparticles on the basis of photoinduced electron transfer. In the presence of target receptors able to bind the quenchers and prevent electron transfer, however, the luminescence of the quantum dots is restored. Thus, complementary receptor-substrate pairs can be identified with luminescence measurements relying on our design logic. In fact, we have demonstrated with a representative example that our protocol can be adapted to signal protein-ligand interactions.