Transfection of living HeLa cells with fluorescent poly-cytosine encapsulated Ag nanoclusters

The fluorescence of silver clusters encapsulated by single stranded oligo-DNA (24 cytosine base pairs, C-24:Ag-n) was used to monitor the transfection of this new silver/DNA fluorophore inside living HeLa cells. For this, the C-24:Ag-n molecules were complexed with a commercially available transfection reagent Lipofectamine and the internalization of C-24:Ag-n was followed with confocal fluorescence microscopy. Bright near-infrared fluorescence was observed from inside the transfected HeLa cells, when exciting with 633 nm excitation, opening up the possibility for the use of these C-24:Ag-n clusters for biological labelling and imaging of living cells and for monitoring the transfection process with limited harm to the living cells.