Amorphous copper(II)-cyanoimidazole frameworks as peroxidase mimics for hydrogen sulfide assay

Melamine enhancing Cu-Fenton reaction for degradation of anthracyclines

Melamine (MA) enhanced Cu-Fenton process was developed for the degradation of anthracyclines. Taking daunorubicin (DNR) degradation as an example, we found that the initial first-order apparent constant of Cu2+/MA/H2O2 system with a molar ratio of 1:8 for Cu2+:MA was 5.2 times higher than that of conventional Cu2+/H2O2 system. The in-situ reductive coordination between Cu2+ and MA facilitated the generation and stabilization of Cu+ species, thereby accelerating the rate-limiting step of Cu2+/Cu+ conversion and maintaining high levels of Cu+ during the degradation process. Moreover, pre-synthesized Cu+-MA complexes (e.g., CM-250) further enhanced the efficiency of the Cu-Fenton reaction by increasing both the Cu+ proportion and MA chelation. The apparent activation energy for DNR degradation in CM-250 mediated Fenton reaction (15.9 kJ mol-1) was lower than that in systems involving Cu2+/MA (41.2 kJ mol-1) and Cu2+ (65.6 kJ mol-1). Enhanced generation of various reactive oxygen species (·OH,·O2-, and 1O2) was confirmed, with 1O2 playing a dominant role, significantly improving both degradation rate and mineralization degree for DNR. MA-enhanced Cu-Fenton process also offers a convenient alternative to effectively remove other anthracyclines and organic micropollutants, holding great promise for advancing advanced oxidation processes as well as practical large-scale degradation applications targeting multiple pollutants.

In Situ Formed 3,3',5,5'-Tetramethylbenzidine-Cu(I/II) Charge-Transfer Complex Intermediates Promoting Colorimetric Assay of Cr6

Developing a synthesis-free, multifunctional, and effective colorimetric assay system based on 3,3',5,5'-tetramethylbenzidine (TMB) oxidation is attractive yet challenging. Herein, we established a synergetic Cu2+/Cr6+-promoting strategy for TMB-based colorimetric detection of Cr6+. By introducing Cu2+, critical TMB·+···Cu(I/II)···TMB charge transfer complex (TMC) intermediates were in situ formed to reduce the activation energy of TMB oxidation, thereby accelerating Cr6+-mediated TMB oxidation. TMC intermediates also played a pivotal role in H2O2-participated TMB oxidation, clarifying the secondary responsibility of reactive oxygen species frequently caused by Fenton-like reactions. Leveraging the synergetic capacity between Cu2+ and Cr6+ for TMB oxidation, we demonstrated sensitive and specific colorimetric detections for Cr6+ with a limit of detection of 0.006 μM. With its convenient operation and rapid responsiveness, this strategy successfully enabled the practical detection of Cr6+ in real water samples. This work not only enhances the understanding of the internal acceleration mechanism in colorimetric sensing but also provides valuable opportunities to advance synthesis-free detection platforms.

Recent Progress and Prospect of Metal-Organic Framework-Based Nanozymes in Biomedical Application

A nanozyme is a nanoscale material having enzyme-like properties. It exhibits several superior properties, including low preparation cost, robust catalytic activity, and long-term storage at ambient temperatures. Moreover, high stability enables repetitive use in multiple catalytic reactions. Hence, it is considered a potential replacement for natural enzymes. Enormous research interest in nanozymes in the past two decades has made it imperative to look for better enzyme-mimicking materials for biomedical applications. Given this, research on metal-organic frameworks (MOFs) as a potential nanozyme material has gained momentum. MOFs are advanced hybrid materials made of inorganic metal ions and organic ligands. Their distinct composition, adaptable pore size, structural diversity, and ease in the tunability of physicochemical properties enable MOFs to mimic enzyme-like activities and act as promising nanozyme candidates. This review aims to discuss recent advances in the development of MOF-based nanozymes (MOF-NZs) and highlight their applications in the field of biomedicine. Firstly, different enzyme-mimetic activities exhibited by MOFs are discussed, and insights are given into various strategies to achieve them. Modification and functionalization strategies are deliberated to obtain MOF-NZs with enhanced catalytic activity. Subsequently, applications of MOF-NZs in the biosensing and therapeutics domain are discussed. Finally, the review is concluded by giving insights into the challenges encountered with MOF-NZs and possible directions to overcome them in the future. With this review, we aim to encourage consolidated efforts across enzyme engineering, nanotechnology, materials science, and biomedicine disciplines to inspire exciting innovations in this emerging yet promising field.