Exploring Selective Fluorescence Turn-On Sensing of Caspase-3 with Molybdenum Disulfide Quenched Copper Nanoclusters: FRET Biosensor

Sensing caspase-3 activity is essential for understanding the role of apoptosis in cancer dynamics, controlling therapeutic strategies, and improving patient care in cancer treatment. In this study, we demonstrate a highly sensitive recombinant human caspase-3 (rhC3) detection technique in biological fluids. This technique uses a copper nanocluster stabilized with bovine serum albumin (BSA-CuNCs) as a metal-based fluorescent biosensor, conjugated with anti-human caspase-3 (ahC3). To turn its fluorescence off, molybdenum disulfide nanosheets (MoS₂ NSs) are added; this partnership is termed ahC3@BSA-CuNCs/MoS₂ nanocouple. In the presence of rhC3, the energy transfer process is affected by strong ahC3/rhC3 interactions. When in close proximity, the rhC3 molecules cause detachment of the nanocluster from the MoS₂ NS surface by attracting the ahC3 component of the nanocluster. This increases the distance between the nanocluster and quencher with a consequent restoration of intensity. As the concentration of rhC3 increases, the fluorescence intensity of the system also increases. A proportional response is seen in the concentration between 0.1 and 1.3 ng/mL with a very low limit of detection of 2.75 pg/mL and a quantification limit of 8.60 pg/mL. A simple filter paper strip was made to visually identify the presence of rhC3 under UV light.