Controlling assembly of paired gold clusters within apoferritin nanoreactor for in vivo kidney targeting and biomedical imaging.

Functional nanostructures with high biocompatibility and stability, low toxicity, and specificity of targeting to desired organs or cells are of great interest in nanobiology and medicine. However, the challenge is to integrate all of these desired features into a single nanobiostructure, which can be applied to biomedical applications and eventually in clinical settings. In this context, we designed a strategy to assemble two gold nanoclusters at the ferroxidase active sites of ferritin heavy chain. Our studies showed that the resulting nanostructures (Au-Ft) retain not only the intrinsic fluorescence properties of noble metal, but gain enhanced intensity, show a red-shift, and exhibit tunable emissions due to the coupling interaction between the paired Au clusters. Furthermore, Au-Ft possessed the well-defined nanostructure of native ferritin, showed organ-specific targeting ability, high biocompatibility, and low cytotoxicity. The current study demonstrates that an integrated multimodal assembly strategy is able to generate stable and effective biomolecule-noble metal complexes of controllable size and with desirable fluorescence emission characteristics. Such agents are ideal for targeted in vitro and in vivo imaging. These results thus open new opportunities for biomolecule-guided nanostructure assembly with great potential for biomedical applications.