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

Abstract

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.

Keywords: Biosensor; Caspase-3; Covalent biofunctionalization; MoS(2) NSs; Polydopamine.