Biocompatible thiolate protected copper nanoclusters for an efficient imaging of lung cancer cells.

We report, the one-pot synthesis of water-soluble and biocompatible 3-mercaptopropylsulfonate (MPS) protected novel copper nanoclusters (CuNCs). Interestingly, the TEM image of MPS protected CuNCs exhibits an ultrasmall nanoclusters of particle size <2-nm, similar to its Au and Ag analogue. The hydrophilic and biocompability property of thiolate protected CuNCs. i.e., MPS stabilized CuNCs and its luminescent nature gave rise to maximum quantum yield of 1.5%. Further, as achieved CuNCs was investigated for haemocompatibility, cell viability and fluorescent microscopic analysis with A549 lung cancer cell line. Haemolytic study was examined using human RBCs in the concentration range of 4 to 22 µg/mL for which 7.5% of haemolysis was obtained for an optimum concentration of 22 µg/mL of CuNCs. The cell viability analysis was carried out by MTT assay using A549 lung cancer cells for the minimum (10 µg/mL) and maximum (45 µg/mL) concentration of CuNCs which reports 93.1% and 38.2% cell viability respectively. The inverted light microscopic images from the control and CuNCs treated (20 µg/mL) cells exhibited an excellent biocompatibility with a normal morphology. Upon increasing the concentration of CuNCs upto 45 µg/mL, the cell viability trends to decrease and the cell morphology also denature gradually. Further, the bio-imaging application of CuNCs was analyzed with A549 lung cancer cells. The efficient imaging with CuNCs treated (20 µg/mL) A549 cells resulted in a green colour emission using FITC filter (460- 490 nm). Thereby the obtained results confirm the applicability of CuNCs for the biomedical and cancer diagnosis applications.