Enhanced stability and fluorescence of mixed-proteins-protected gold/silver clusters used for mercury ions detection

- Largely enhanced fluorescence is found for the BSA-Lyz Au/Ag NCs.
- The BSA-Lyz Au/Ag NCs exhibited high selectivity for Hg2+ over other metal ions.
- The limit of detection of BSA-Lyz Au NCs was as low as 0.7 nM for Hg2+.
- The Hg2+ probe (BSA-Lyz Au NCs) is of low cytotoxicity and can be used in living cell imaging.

We have synthesized gold/silver nanoclusters (NCs) under the protection of both bovine-serum-albumin (BSA) and lysozyme (Lyz) and found that the NCs protected by the mixed-proteins give rise to largely enhanced stability and fluorescence, enabling promising applications for chemosensing and bioimaging. The enhanced fluorescence of Au NCs was found to be exclusively quenched at the presence of Hg2+ ions with an ultralow detection limit up to ∼0.7 nM. It is also interesting to find that the BSA-Lyz-Au NCs are nontoxic and available for fluorescence imaging of Hg2+ detection in MCF-7 cells. The low cytotoxicity, good penetrability and fluorescence sensitivity of BSA-Lyz-Au NCs suggest promising biological applications. Similar observations were also addressed for the Ag system, indicating general applicability of this facile strategy based on BSA-Lyz mixed proteins for the protection of metal NCs.

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