Given the promising prospect of nanozymes in colorimetric test strips, it is essential to eliminate the interferences of their multi-activities and various colors on the test strip. Now, researchers from the Qingdao Agricultural University, led by Professor Lei Han, have synthesized a white Mn-based metal-organic framework nanozymes with ultrathin 2D morphology. This nanozymes has a single peroxidase-like activity and can effectively resist O₂ and color interference. This work provides a promising route for systematically studying the white origin of nanozymes, improving their substrate selectivity and resisting interference.

Why Mn-MOF Matters

Reaction specificity: Mn-MOF nanozyme has a single peroxidase-like activity but no oxidase-like activity. The reaction must be started by adding of H₂O₂, which can effectively resist the interference of O₂ during the detection process.

Substrate specificity: Mn-MOF nanozymes can specifically catalyze the oxidation of substrate TMB without additional modification, but cannot oxidize other substrates such as ABTS, OPD and DAB.

Whitening effect: The addition of white Mn-MOF nanozymes to commercial white paper can effectively whiten it and improve the sensitivity of the colorimetric results of the test strip.

Innovative Design and Features

Causes of white: The whiteness of Mn-MOF originates from specific metal-ligand combinations rather than the nanostructure-induced scattering effects and defect-state luminescence. The luminance value and whiteness index of Mn-MOF are 93.09 and 93.78 respectively, and the total color difference from standard white TiO₂ is less than 1. This material does not absorb visible light and produces high diffuse reflectance (about 90%).

Mild synthesis method: Mn-MOF is synthesized by a mild ultrasonic method, without the need for high temperature, high pressure or sealed equipment.

Avoid color interference: The white Mn-MOF nanozymes avoids the interference of the material color itself on the color of the chromogenic substrate on the test paper, thereby improving the accuracy and sensitivity of the detection.

Applications and Future Outlook

Nanozymes-based test strip: The detection of test strips based on Mn-MOF nanozymes has high sensitivity, low cost, good storage stability, and good reliability for the detection of actual samples.

Detection universality: The detection platform based on Mn-MOF nanozymes has extremely high sensitivity for H₂O₂ detection. Based on this, a series of test strips for detecting glucose and creatinine have been developed, demonstrating excellent universality.

Challenges and Prospects: The transformation of paper-based sensors from academic research to commercial application still faces many challenges. Looking forward, the marriage of tunable MOF optics with enzymatic specificity opens transformative possibilities.

This study demonstrates the outstanding detection capabilities and promising application potential of white single-active nanozyme materials, which will inspire more researchers to conduct studies on white nanozymes.

Stay tuned for more breakthroughs from Professor Han’s teams at Qingdao Agricultural University!

White Mn-MOF nanozymes with peroxidase-activity specificity overcome color and O2 effects on colorimetric test strips