The Pd nanoparticles-modified porphyrin metal-organic framework as highly efficient oxidase mimics for colorimetric quantification and discrimination of oleuropein

Given the limitations associated with conventional methods for oleuropein (OLE) analysis, such as their high cost, lengthy analysis time, and complex sample preparation procedures, this study proposed a novel colorimetric sensing assay based on nanozyme technology, with a specific focus on PCN-224-Pd composite materials. PCN-224 exhibited distinctive structural characteristics and possessed a substantial specific surface area, making it an ideal dispersion platform for Pd nanoparticles. This effectively enhanced the catalytic activity and stability of the nanozyme. Technologies such as transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES), and fourier-transform infrared spectroscopy (FTIR) were employed to comprehensively characterize the morphology, structure, and composition of the synthesized PCN-224-Pd. Experimental characterizations revealed that PCN-224-Pd exhibited high affinity and the origin of PCN-224-Pd as oxidase mimics was likely dependent on the conversion of dissolved oxygen to 1 O 2 and •OH. Under optimal catalytic conditions, we developed a colorimetric sensing assay for oleuropein with an extended linear range (0.1–400 μg/mL) and an impressively low detection limit (9.7 ng/mL). These results indicated that the PCN-224-Pd based method held immense potential for practical applications as it could serve as a visual inspection technique for detecting oleuropein.