Single-Particle Plasmonic Sensing of Nitric Oxide in Living Cells

Plasmon resonance energy transfer (PRET), which occurs between plasmonic nanoparticles (NPs) and organic dyes, shows significant potential in sensing chemistry due to its high sensitivity at the single-particle level. In this work, a PRET-based sensing strategy was presented for the ultrasensitive sensing of nitric oxide (NO) in living cells. Supramolecular cyclodextrin (CD) molecules that exhibited different binding abilities to various molecules due to its unique rigid structure and annular cavity was applied and modified on gold NPs (GNPs) to construct the PRET nanosensors. NO-reactive molecules, rhodamine B-derived molecules (RdMs), were further inserted into the cavity of CD molecules through hydrophobic interactions to form host-guest structures. In the presence of NO, RdMs reacted with the target and generated rhodamine (RdB). Due to the spectral overlap between GNPs@CD and RdB molecules, PRET occurred and further led to a decrease in the scattering intensity of GNPs@CD, which was sensitive to the concentration of NO. The proposed sensing platform not only provides quantitative detection of NO in solution but also realized the single-particle imaging analysis of exogenous and endogenous NO in living cells. The single-particle plasmonic probes exhibit great potential in the in vivo sensing of biomolecules and metabolic processes.