Multifunctional SAzymes-in-MOF Hybrids: Single-Atom Cu-Doped Carbon Dots@Zr-MOF Polyhedra for Highly Sensitive PEC-RGB Dual-Mode Assay of ATP

The highly sensitive and reliable assay of adenosine triphosphate (ATP) is of great significance for disease diagnosis and treatment. Here, a novel photoelectrochemical (PEC) and red-green-blue (RGB) colorimetric dual-mode biosensing platform was developed for the ATP assay based on the multifunctional single-atom nanozymes (SAzymes)-in-metal organic framework (MOF) hybrids. First, small-sized single-atom Cu-doped carbon dots (SA Cu-CDs) with excellent peroxidase-like activity and high electronic conductivity were in situ encapsulated in Zr-MOF (porous coordination network-224, PCN-224), forming multifunctional SAzymes-in-MOF hybrids (SA Cu-CDs@PCN-224). Then, the SA Cu-CDs@PCN-224 hybrids were immobilized on the amino-functionalized indium tin oxide (NH 2 -ITO) electrode via the 1-(3-(dimethylamino)propyl)-3-ethyl-carbodiimide hydrochloride (EDC)/ N -hydroxysuccinimide (NHS) cross-linking reaction. When ATP was present, the destruction of PCN-224 occurred due to the formation of Zr–O–P bonds, releasing SA Cu-CDs from SA Cu-CDs@PCN-224 hybrids. The released SA Cu-CDs triggered a turn-on blue signal through a catalytic chromogenic reaction in the RGB mode, while the destruction of PCN-224 resulted in a turn-off photocurrent signal in the PEC mode. Hence, a highly sensitive and reliable assay of ATP was carried out with wide linear response ranges (0.5–2000 nM for PEC and 5–2000 nM for RGB) and low detection limits (0.12 nM for PEC and 1.08 nM for RGB). The innovative design of SAzymes-in-MOF hybrids provides a new preparation strategy of multifunctional probes for PEC-RGB dual-mode assays, and the developed SA Cu-CDs@PCN-224 hybrids and a PEC-RGB dual-mode biosensing platform may have great potential application in bioanalysis and disease diagnostics.