Efficient biofunctionalization of MoS2 nanosheets with peptides as intracellular fluorescent biosensor for sensitive detection of caspase-3 activity.

Intracellular detection of caspase-3 activity is crucial for the study of cell apoptosis and caspase-3 related diseases. Although various nanomaterials-based biosensors have been constructed for this purpose, they often suffer from poor stability or complicated construction due to the lack of a facile and efficient biofunctionalization method, which decreases their sensing performance and limits their use in the complex physiological environments. As novel two-dimentional (2D) nanomaterials, MoS2 nanosheets (NSs) have shown great potential for biosensing due to their unique properties. Herein, we develop a versatile yet facile covalent biofucntionalization strategy of MoS2 NSs by utilizing polydopamine (PDA) as nano-bio interface, and construct an intracellular fluorescent biosensor (MoS2@PDA-PEG-Peptide, MPPP) for the determination of caspase-3 activity. This covalent biofunctionalization of MoS2 NSs can significantly improve the conjugation efficiency of biomolecules and enhance their stability in complicated environments, which is much better than conventional biofunctionalization by using thiol-metal coordination. Furthermore, this novel caspase-3 biosensor based on peptides biofunctionalized MoS2 NSs shows high sensitivity and selectivity for the detection of caspase-3 with a limit of detection (LOD) of 0.33 ng/mL, and can be used for high-contrast fluorescent imaging of cell apoptosis.