Receptor-Targeted Luminescent Silver Bionanoparticles

Luminescent Ag nanoclusters (Ag‐NC) provide the next generation in bionanoparticles, wherein the luminescence (650 nm) and large Stokes shift of these inorganic nanoclusters are favorable for biological imaging. By combining these characteristics with those of human serum albumin (HSA; a protein capable of binding multiple endo‐ and exogenous compounds), the Ag nanoclusters can be shielded from the environment and functionalized with (receptor) targeting moieties. Encapsulation of the 1.5 nm Ag nanoclusters by HSA resulted in a threefold increase in luminescence intensity and a twofold increase of the luminescence lifetime (1.7 vs. 3.6 µs). To exemplify the potential of this targeted concept, we functionalized HSA‐Ag nanoparticles with chemokine receptor 4 (CXCR4) targeting peptides [Ac‐TZ14011(CO2H)]. The resulting Ac‐TZ14011‐HSA‐Ag nanoparticles demonstrated specific binding to CXCR4‐overexpressing tumor cells. Upon exposure to (ambient) light, particle‐functionalized tumor cells were killed. Combined, these experiments illustrate that HSA‐Ag nanoparticles may have a potential in biological imaging and possibly even in targeted theranostic applications. Luminescent silver nanoclusters can be encapsulated by human serum albumin, resulting in improved optical properties. This protein scaffold can be further functionalized with targeting moieties, resulting in HSA‐Ag nanoparticles that can be applied as targeted imaging agents and possibly even as theranostic agents.