Highly stable folic acid functionalized copper-nanocluster/silica nanoparticles for selective targeting of cancer cells

In this paper, we present a novel strategy to construct folic acid functionalized conjugated Cu nanoclusters (CuNCs) and silica (SiO(2)) nanocomposites for targeted detection of cancer cells. First of all, BSA capped CuNCs were encapsulated into a SiO(2) matrix. The resulting CuNCs@SiO(2) nanoparticles showed bright red fluorescence with an enhanced photoluminescence quantum yield compared with free CuNCs, as well as improved stability in a complex biological environment owning to the protection of the SiO(2) matrix. Upon attachment of folic acid via the poly-l-lysine conjugates (PLL-FA) on the surface of CuNCs@SiO(2) driven by electrostatic interaction, the as-prepared CuNCs@SiO(2)/PLL-FA nanocomposites are capable of selectively recognizing folate receptor (FR) over-expressed cancer cells rather than FR-negative cells. The cell viability assay proved the low biotoxicity of CuNCs@SiO(2)/PLL-FA nanocomposites toward living cells and the in vitro cellular imaging assay results demonstrated their selective endocytosis of FR-positive cells (KB cells), bringing about red fluorescence labeling within the cells. Intriguingly, our strategy provides a novel route to synthesize functional CuNCs@SiO(2)/PLL-FA nanocomposites equipped with superior fluorescence properties, high stability against external stimuli and good biocompatibility, and have great application potential in bioimaging imaging and targeted cell detection.