Multifunctional SAzymes-in-MOF Hybrids: Single-Atom Cu-Doped Carbon Dots@Zr-MOF Polyhedra for Highly Sensitive...

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 (NH₂-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.