Using Cu-Based Metal-Organic Framework as a Comprehensive and Powerful Antioxidant Nanozyme for Efficient Osteoarthritis Treatment.

Developing nanozymes with effective reactive oxygen species (ROS) scavenging ability is a promising approach for osteoarthritis (OA) treatment. Nonetheless, numerous nanozymes lie in their relatively low antioxidant activity. In certain circumstances, some of these nanozymes may even instigate ROS production to cause side effects. To address these challenges, a copper-based metal-organic framework (Cu MOF) nanozyme is designed and applied for OA treatment. Cu MOF exhibits comprehensive and powerful activities (i.e., SOD-like, CAT-like, and •OH scavenging activities) while negligible pro-oxidant activities (POD- and OXD-like activities). Collectively, Cu MOF nanozyme is more effective at scavenging various types of ROS than other Cu-based antioxidants, such as commercial CuO and Cu single-atom nanozyme. Density functional theory calculations also confirm the origin of its outstanding enzyme-like activities. In vitro and in vivo results demonstrate that Cu MOF nanozyme exhibits an excellent ability to decrease intracellular ROS levels and relieve hypoxic microenvironment of synovial macrophages. As a result, Cu MOF nanozyme can modulate the polarization of macrophages from pro-inflammatory M1 to anti-inflammatory M2 subtype, and inhibit the degradation of cartilage matrix for efficient OA treatment. The excellent biocompatibility and protective properties of Cu MOF nanozyme make it a valuable asset in treating ROS-related ailments beyond OA.

Bioinspired structural hydrogels with highly ordered hierarchical orientations by flow-induced alignment of nanofibrils.

Natural structural materials often possess unique combinations of strength and toughness resulting from their complex hierarchical assembly across multiple length scales. However, engineering such well-ordered structures in synthetic materials via a universal and scalable manner still poses a grand challenge. Herein, a simple yet versatile approach is proposed to design hierarchically structured hydrogels by flow-induced alignment of nanofibrils, without high time/energy consumption or cumbersome postprocessing. Highly aligned fibrous configuration and structural densification are successfully achieved in anisotropic hydrogels under ambient conditions, resulting in desired mechanical properties and damage-tolerant architectures, for example, strength of 14 ± 1 MPa, toughness of 154 ± 13 MJ m-3, and fracture energy of 153 ± 8 kJ m-2. Moreover, a hydrogel mesoporous framework can deliver ultra-fast and unidirectional water transport (maximum speed at 65.75 mm s-1), highlighting its potential for water purification. This scalable fabrication explores a promising strategy for developing bioinspired structural hydrogels, facilitating their practical applications in biomedical and engineering fields.

A Rational Design of Metal-Organic Framework Nanozyme with High-Performance Copper Active Centers for Alleviating Chemical Corneal Burns.

Metal-organic frameworks (MOFs) have attracted significant research interest in biomimetic catalysis. However, the modulation of the activity of MOFs by precisely tuning the coordination of metal nodes is still a significant challenge. Inspired by metalloenzymes with well-defined coordination structures, a series of MOFs containing halogen-coordinated copper nodes (Cu-X MOFs, X = Cl, Br, I) are employed to elucidate their structure-activity relationship. Intriguingly, experimental and theoretical results strongly support that precisely tuning the coordination of halogen atoms directly regulates the enzyme-like activities of Cu-X MOFs by influencing the spatial configuration and electronic structure of the Cu active center. The optimal Cu-Cl MOF exhibits excellent superoxide dismutase-like activity with a specific activity one order of magnitude higher than the reported Cu-based nanozymes. More importantly, by performing enzyme-mimicking catalysis, the Cu-Cl MOF nanozyme can significantly scavenge reactive oxygen species and alleviate oxidative stress, thus effectively relieving ocular chemical burns. Mechanistically, the antioxidant and antiapoptotic properties of Cu-Cl MOF are achieved by regulating the NRF2 and JNK or P38 MAPK pathways. Our work provides a novel way to refine MOF nanozymes by directly engineering the coordination microenvironment and, more significantly, demonstrating their potential therapeutic effect in ophthalmic disease.

Using Wool Keratin as a Structural Biomaterial and Natural Mediator to Fabricate Biocompatible and Robust Bioelectronic Platforms.

The design and fabrication of biopolymer-incorporated flexible electronics have attracted immense interest in healthcare systems, degradable implants, and electronic skin. However, the application of these soft bioelectronic devices is often hampered by their intrinsic drawbacks, such as poor stability, inferior scalability, and unsatisfactory durability. Herein, for the first time, using wool keratin (WK) as a structural biomaterial and natural mediator to fabricate soft bioelectronics is presented. Both theoretical and experimental studies reveal that the unique features of WK can endow carbon nanotubes (CNTs) with excellent water dispersibility, stability, and biocompatibility. Therefore, well-dispersed and electroconductive bio-inks can be prepared via a straightforward mixing process of WK and CNTs. The as-obtained WK/CNTs inks can be directly exploited to design versatile and high-performance bioelectronics, such as flexible circuits and electrocardiogram electrodes. More impressively, WK can also be a natural mediator to connect CNTs and polyacrylamide chains to fabricate a strain sensor with enhanced mechanical and electrical properties. With conformable and soft architectures, these WK-derived sensing units can be further assembled into an integrated glove for real-time gesture recognition and dexterous robot manipulations, suggesting the great potential of the WK/CNT composites for wearable artificial intelligence.

ZIF-90 with biomimetic Zn-N coordination structures as an effective nanozyme to mimic natural hydrolase.

Inspired by the structures of enzymes, a fast and robust strategy for generating ZIF-90 metallo-nanozymes is presented. The Zn-N coordination structure in ZIF-90 can closely imitate the catalytic center of a natural zinc-based hydrolase. As expected, ZIF-90 possesses potent hydrolase-mimicking activity, high stability and excellent recyclability.

Using Wool Keratin Derived Metallo-Nanozymes as a Robust Antioxidant Catalyst to Scavenge Reactive Oxygen Species Generated by Smoking.

Self-assembled nanostructures based on biomolecules (e.g., proteins and amino acids) and metal ions have promising applications in mimicking the nanostructure, properties, and functions of natural enzymes. Herein, a metal ion-mediated self-assembly method for constructing catalytically active Cu-wool-keratin (CuWK) two-dimensional nanozymes is presented. Specifically, by introducing copper ions as abiological cofactors, WK can serve as a protein scaffold to design and create Cu catalytic sites. The optimized hybrids with Cu-WK coordination framework exhibit significant superoxide dismutases-like activity, catalase-like activity, and hydroxyl radical scavenging ability. These combined antioxidant activities make CuWK a robust nanozyme to effectively remove various reactive oxygen species (ROS). In this work, the as-prepared CuWK as a new additive can be integrated into a cigarette filter system to effectively remove the produced ROS from the burning of tobacco. More importantly, the CuWK nanozymes as a critical element can be further utilized to construct a recycling cigarette holder. Therefore, the present work shows that nanozymes with advanced catalytic capabilities can be constructed by self-assembly of metal ions and proteins, thus facilitating the rational design and discovery of this kind of artificial metalloenzymes.

Cu2+ and Fe2+ Sensor Based on CdTe QD@ZIF-8 Composites.

TGA capped CdTe QDs have been encapsulated in miroporous ZIF-8, with no obvious deterioration of their photoluminescence property. The resulted CdTe QD@ZIF-8 composites show a higher luminescent stability in various buffer solution. The material has successfully been used as a luminescent indicator for the detection of Cu2+ and Fe2+ ions. The luminescence of CdTe QD@ZIF-8 composite quenches only in the presence of Cu2+ or Fe2+ ions. The linear ranges of detection have been estimated as 1~50 uM for Cu2+ ions and 1~60 uM for Fe2+ ions, respectively. A "competing transmission" mechanism has been proposed to explain the selectivity of the sensor to detecting Cu2+ and Fe2+ ions. Luminescent quenching can only occurred when the bonding power of QD surface surpasses the adsorptivity of the outside ZIF-8 to the metal ions.