Unraveling the Enzymatic Activity of Oxygenated Carbon Nanotubes and Their Application in the Treatment of Bacterial Infections

Abstract

Carbon nanotubes (CNTs) and their derivatives have emerged as a series of efficient biocatalysts to mimic the function of natural enzymes in recent years. However, the unsatisfiable enzymatic efficiency usually limits their practical usage ranging from materials science to biotechnology. Here, for the first time, we present the synthesis of several oxygenated-group-enriched carbon nanotubes (o-CNTs) via a facile but green approach, as well as their usage as high-performance peroxidase mimics for biocatalytic reaction. Exhaustive characterizations of the enzymatic activity of o-CNTs have been provided by exploring the accurate effect of various oxygenated groups on their surface including carbonyl, carboxyl, and hydroxyl groups. Because of the "competitive inhibition" effect among all of these oxygenated groups, the catalytic efficiency of o-CNTs is significantly enhanced by weakening the presence of noncatalytic sites. Furthermore, the admirable enzymatic activity of these o-CNTs has been successfully applied in the treatment of bacterial infections, and the results of both in vitro and in vivo nanozyme-mediated bacterial clearance clearly demonstrate the feasibility of o-CNTs as robust peroxidase mimics to effectively decrease the bacterial viability under physiological conditions. We believe that the present study will not only facilitate the construction of novel efficient nanozymes by rationally adjusting the degree of the "competitive inhibition" effect, but also broaden the biological usage of o-CNT-based nanomaterials via their satisfactory enzymatic activity.

Revealing the Intrinsic Peroxidase-Like Catalytic Mechanism of Heterogeneous Single-Atom Co–MoS2

“…The atomistic-level exploration of the original active sites of nanozymes is mainly performed by simplifying the singlecomponent catalysts of noble metal nanoparticles [8][9][10], transition metal oxides [11], and carbon-based materials [12,13]. The cascade reactions catalyzed by multiple enzymes in an organism provide great impetus for preparing composite catalysts by integrating different kinds of nanozymes to mimic the complexity of biocatalysis [14,15].…”

Defect‐Rich Adhesive Nanozymes as Efficient Antibiotics for Enhanced Bacterial Inhibition

“…Next, the defect-rich active edges of our efficient nanozymes motivated us to evaluate their catalytic performance.A s shown in Figure 3a,a ll the adhesive nanozymes with defectrich active edges exhibited higher peroxidase-like activity than pristine MoS 2 .T heir catalytic mechanism was explored by fluorescent experiments and density functional theory (DFT) calculations.E mploying terephthalic acid (TA) as atracking probe,wefound that the peroxidase-like activity of MoS 2 -based nanozymes was derived from their ability to convert H 2 O 2 into COH radicals (Supporting Information, Figure S13), which was in accordance with previous studies. [4,8,10,11] Further, we built three typical models of MoS 2 (pristine MoS 2 ,S-defect MoS 2 ,and MoS 2 with Mo and Sedge) to explore the H 2 O 2 activation process (adsorption-homolysis-desorption), shown in Figure S14 in the Supporting Information. Figure 3c and Figures S15-20 in the Supporting Information showed the optimized structures of important intermediates during the H 2 O 2 -decomposition process as well as the adsorption energies.I tw as clearly seen that the H 2 O 2 molecule was stably adsorbed on MoS 2 ,onS-defect MoS 2 ,and on the edge of MoS 2 with adsorption energies of À0.14, À0.32, and À0.47 eV,r espectively.F urthermore,a ll intermediates have negative adsorption energies,s uggesting as table adsorption.…”

“…[2,3] Recently,the burgeoning nanozymes have emerged as anew generation of antibiotics due to their broad-spectrum antimicrobial activity,n egligible toxicity,a nd the lack of resistance towards nanozymes. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Typically,ananozyme that acts as ap eroxidase mimic specifically catalyzes the con-version of H 2 O 2 into highly toxic reactive oxygen species (ROS), such as hydroxyl radical (COH), to attack the bacterial membrane at mildly acidic infectious sites.H owever,t he insufficient bacteria-capturing capacity of nanostructures as well as the relatively low ability to generate ROS,i nherent short lifespan, and limited diffusion distance of ROSseverely restrict the therapeutic activity of almost all nanozymes. [19,20] To overcome this issue,integration of multiple components or surface-modification strategies have been applied to improve the antibacterial effects, [4,9,10,13,14] but this comes out at the cost of either wasting antimicrobial material or blocking active sites,a nd could even cause toxicity.T herefore,i ti s urgently needed to find an ew way to engineer nanozymes with both inherent bacteria-binding ability and enhanced catalytic activity to improve their therapeutic outcomes without potential safety hazards.…”

Antibiotic‐Free Antibacterial Strategies Enabled by Nanomaterials: Progress and Perspectives

“…Qu and co‐workers proposed the “competitive effect” of carboxyl and hydroxyl groups for carbon nanotube (CNT)‐based nanozymes. Oxygenated groups enriched CNTs with carbonyl groups as active centers were fabricated, reaching the highest peroxidase‐like catalytic activity for bacterial infection treatment …”