Chaoqun Liu

Copper(II)–Graphitic Carbon Nitride Triggered Synergy: Improved ROS Generation and Reduced Glutathione Levels for Enhanced Photodynamic Therapy

Graphitic carbon nitride (g-C3 N4 ) has been used as photosensitizer to generate reactive oxygen species (ROS) for photodynamic therapy (PDT). However, its therapeutic efficiency was far from satisfactory. One of the major obstacles was the overexpression of glutathione (GSH) in cancer cells, which could diminish the amount of generated ROS before their arrival at the target site. Herein, we report that the integration of Cu(2+) and g-C3 N4 nanosheets (Cu(2+) -g-C3 N4 ) led to enhanced light-triggered ROS generation as well as the depletion of intracellular GSH levels. Consequently, the ROS generated under light irradiation could be consumed less by reduced GSH, and efficiency was improved. Importantly, redox-active species Cu(+) -g-C3 N4 could catalyze the reduction of molecular oxygen to the superoxide anion or hydrogen peroxide to the hydroxyl radical, both of which facilitated the generation of ROS. This synergy of improved ROS generation and GSH depletion could enhance the efficiency of PDT for cancer therapy.

Self-Assembly of Multi-nanozymes to Mimic an Intracellular Antioxidant Defense System

In this work, for the first time, we constructed a novel multi-nanozymes cooperative platform to mimic intracellular antioxidant enzyme-based defense system. V2 O5 nanowire served as a glutathione peroxidase (GPx) mimic while MnO2 nanoparticle was used to mimic superoxide dismutase (SOD) and catalase (CAT). Dopamine was used as a linker to achieve the assembling of the nanomaterials. The obtained V2 O5 @pDA@MnO2 nanocomposite could serve as one multi-nanozyme model to mimic intracellular antioxidant enzyme-based defense procedure in which, for example SOD, CAT, and GPx co-participate. In addition, through assembling with dopamine, the hybrid nanocomposites provided synergistic antioxidative effect. Importantly, both in vitro and in vivo experiments demonstrated that our biocompatible system exhibited excellent intracellular reactive oxygen species (ROS) removal ability to protect cell components against oxidative stress, showing its potential application in inflammation therapy.

An Efficient and Benign Antimicrobial Depot Based on Silver-Infused MoS2

Silver nanoparticles (AgNPs) have been used as a broad-spectrum antimicrobial agent, whose toxicity originates from the localized release of Ag+ ions. However, the residual AgNPs core could generate potential risk to humans and waste of noble metals. Herein, we infused the cysteine-modified molybdenum disulfide with minimum Ag+ ions and coated with a layer of cationic polyelectrolyte to construct an efficient and benign antimicrobial depot. The system exhibited much enhanced broad-spectrum antibacterial activity compared with an equivalent amount of silver nitrate, owing to its increasing accessibility of released Ag+ to the cell walls of microorganisms. More importantly, the antibacterial system could be successfully applied to treat wound infection, while retaining high antibacterial activities, exhibiting negligible biotoxicity and avoiding the waste of Ag.

Nanozyme Decorated Metal–Organic Frameworks for Enhanced Photodynamic Therapy

Metal-organic frameworks (MOFs) have been used for photodynamic therapy (PDT) of cancers by integrating photosensitizers, which cause cytotoxic effects on cancer cells by converting tumor oxygen into reactive singlet oxygen (1O2). However, the PDT efficiency of MOFs is severely limited by tumor hypoxia. Herein, by decorating platinum nanozymes on photosensitizer integrated MOFs, we report a simple yet versatile strategy for enhanced PDT. The platinum nanoparticles homogeneously immobilized on MOFs possess high stability and catalase-like activity. Thus, our nanoplatform can facilitate the formation of 1O2 in hypoxic tumor site via H2O2-activated evolvement of O2, which can cause more serious damage to cancer cells. Our finding highlights that the composites of nanozymes and MOFs have the potential to serve as efficient agents for cancer therapy, which will open an avenue of nanozymes and MOFs toward biological applications.

A Multinuclear Metal Complex Based DNase-Mimetic Artificial Enzyme: Matrix Cleavage for Combating Bacterial Biofilms.

Extracellular DNA (eDNA) is an essential structural component during biofilm formation, including initial bacterial adhesion, subsequent development, and final maturation. Herein, the construction of a DNase-mimetic artificial enzyme (DMAE) for anti-biofilm applications is described. By confining passivated gold nanoparticles with multiple cerium(IV) complexes on the surface of colloidal magnetic Fe3 O4  /SiO2 core/shell particles, a robust and recoverable artificial enzyme with DNase-like activity was obtained, which exhibited high cleavage ability towards both model substrates and eDNA. Compared to the high environmental sensitivity of natural DNase in anti-biofilm applications, DMAE exhibited a much better operational stability and easier recoverability. When DMAE was coated on substratum surfaces, biofilm formation was inhibited for prolonged periods of time, and the DMAE excelled in the dispersion of established biofilms of various ages. Finally, the presence of DMAE remarkably potentiated the efficiency of traditional antibiotics to kill biofilm-encased bacteria and eradiate biofilms.

Specific Oxygenated Groups Enriched Graphene Quantum Dots as Highly Efficient Enzyme Mimics

Significant progress is achieved for the utilization of graphene quantum dots as enzyme mimics in various biomedical fields recently. Although promising, the biocatalytic performance is far from satisfactory. Here, the rational design and synthesis of specific oxygenated groups enriched graphene quantum dots (o-GQDs) via a facile oxidation reflux route is reported. These well-prepared o-GQDs with uniform size exhibit an ultrahigh peroxidase-like activity in a wide range of pH values, and their superior performance is verified by using glucose detection as a typical model. Compared with classical nanozymes, these o-GQDs show multiple times higher enzymatic activity. It is believed that the super facile synthesis strategy can greatly facilitate the practical use of o-GQDs as enzyme mimics in the future.

Selenium-Based Nanozyme as Biomimetic Antioxidant Machinery

A self-assembly nanocomposite was designed to mimic intracellular enzymatic and non-enzymatic antioxidants-constituted antioxidant defense machinery. In this work, selenium nanocomponent served as one model to mimic antioxidant enzyme, whereas polydopamine was able to mimic non-enzymatic antioxidant biomolecule in living systems. With the excellent glutathione peroxidase-mimic capacity of selenium and the reducibility of polydopamine, this Se@pDA nanozyme could achieve synergetic antioxidative efficiency to protect cellular components against oxidative damage. The pneumonia model of mice further proved the potential of our nanocomposites for anti-inflammation therapy.

Nanozyme as Artificial Receptor with Multiple Readouts for Pattern Recognition

Nanozymes have been widely used for the construction of colorimetric sensors. However, the simultaneous discrimination of multiple targets using nanozymes is still a challenge. In this work, we construct a multiple-readout system for pattern recognition of proteins using nanozyme. Graphitic carbon nitride (g-C3N4) nanosheets, which possess peroxidase-like activity, are chosen as the single sensing receptor. The catalytic activity of g-C3N4 can be changed to different degrees owing to the different interactions between g-C3N4 and proteins. By choosing different combinations of absorbance intensities at various time points, multichannel information can be extracted from a single material for pattern recognition. The platform avoids the synthesis of multiplex sensing receptors and the requirement of sophisticated instruments, leading to lower cost and time consumption. The study provides a new method for the construction of feasible, convenient, and flexibly nanozyme-based sensing arrays.