Exploring\nSelective Fluorescence Turn-On Sensing of\nCaspase‑3 with Molybdenum Disulfide Quenched Copper Nanoclusters:\nFRET Biosensor

Sensing\ncaspase-3 activity is essential for understanding the role\nof apoptosis in cancer dynamics, controlling therapeutic strategies,\nand improving patient care in cancer treatment. In this study, we\ndemonstrate a highly sensitive recombinant human caspase-3 (rhC3)\ndetection technique in biological fluids. This technique uses a copper\nnanocluster stabilized with bovine serum albumin (BSA-CuNCs) as a\nmetal-based fluorescent biosensor, conjugated with anti-human caspase-3\n(ahC3). To turn its fluorescence off, molybdenum disulfide nanosheets\n(MoS<sub>2</sub> NSs) are added; this partnership is termed ahC3@BSA-CuNCs/MoS<sub>2</sub> nanocouple. In the presence of rhC3, the energy transfer\nprocess is affected by strong ahC3/rhC3 interactions. When in close\nproximity, the rhC3 molecules cause detachment of the nanocluster\nfrom the MoS<sub>2</sub> NS surface by attracting the ahC3 component\nof the nanocluster. This increases the distance between the nanocluster\nand quencher with a consequent restoration of intensity. As the concentration\nof rhC3 increases, the fluorescence intensity of the system also increases.\nA proportional response is seen in the concentration between 0.1 and\n1.3 ng/mL with a very low limit of detection of 2.75 pg/mL and a quantification\nlimit of 8.60 pg/mL. A simple filter paper strip was made to visually\nidentify the presence of rhC3 under UV light.