Highly selective light scattering imaging of chromium (III) in living cells with silver nanoparticles

In this contribution, we present a highly selective chromium ion (Cr³⁺)-induced aggregation of citrate-capped silver nanoparticles, which could be applied for the imaging of the distribution of Cr³⁺ in cells. It was found that selective aggregation of citrate-capped silver nanoparticles occurs at room temperature in the presence of Cr³⁺ in aqueous medium of pH 6.8, resulting in color change from yellow to pink in 10 min and enhanced localized surface plasmon resonance (LSPR) scattering signals. Tenfold of other metal ions including Al³⁺, Ca²⁺, Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Hg²⁺, La³⁺, Mg²⁺, Ni²⁺, Pb²⁺, Tb³⁺ and Zn²⁺ had no response. Mechanism analysis showed that the aggregation is mainly dependent on the chelation of Cr³⁺ ion with the citrate ion capped on silver nanoparticles, forming crosslinking aggregates of silver nanoparticles. With the Cr³⁺-induced enhancement of LSPR scattering signals, Cr³⁺ in cytoplasm of human bone marrow neuroblastoma cells could be imaged with dark-field light scattering imaging technique.