Highly Luminescent Folate-Functionalized Au₂₂ Nanoclusters for Bioimaging

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Materials Science

Background:

• Gold nanoclusters offer unique properties for biomedical applications due to their small size and biocompatibility.
• Developing highly luminescent and stable nanoprobes is crucial for advanced bioimaging.

Purpose of the Study:

• To synthesize and characterize a novel folate-functionalized gold nanocluster (Au22-FA) with enhanced luminescence for biomedical applications.
• To evaluate the optical, biological, and in vivo properties of Au22-FA for bioimaging.

Main Methods:

• Synthesis of Au22-FA clusters by functionalizing Au22(SG)18 with benzyl chloroformate and folate.
• Optical characterization including luminescence quantum yield and brightness measurements.
• Biological evaluation including cell viability, target specificity, and in vivo imaging in mice.

Main Results:

• Au22-FA clusters exhibit high water solubility and significantly enhanced luminescence (42% quantum yield, 8-fold brighter than Au22(SG)18).
• The nanoclusters demonstrate excellent photostability, low toxicity (80% cell viability at 1000 ppm), and target specificity to folate-receptor positive cells.
• In vivo studies showed rapid renal clearance, with only 8% remaining after 24 hours post-injection.

Conclusions:

• Folate-functionalized gold nanoclusters (Au22-FA) represent a promising new class of luminescent nanomaterials for targeted bioimaging.
• The enhanced brightness, stability, low toxicity, and efficient clearance profile make Au22-FA suitable for various biomedical applications.