Stepwise Protonation of Three-Dimensional Covalent Organic Frameworks for Enhancing Hydrogen Peroxide Photosynthesis.

Three-dimensional covalent organic frameworks (3D COFs), recognized for their tailorable structures and accessible active sites, offer a promising platform for developing advanced photocatalysts. However, the difficulty in the synthesis and functionalization of 3D COFs hinders their further development. In this study, we present a series of 3D-bcu-COFs with 8 connected porphyrin units linked by linear linkers through imine bonds as a versatile platform for photocatalyst design. The photoresponse of 3D-bcu-COFs was initially modulated by functionalizing linear linkers with benzo-thiadiazole or benzo-selenadiazole groups. Furthermore, taking advantage of the well-exposed porphyrin and imine sites in 3D-bcu-COFs, their photocatalytic activity was optimized by stepwise protonation of imine bonds and porphyrin centers. The dual protonated COF with benzo-selenadiazole groups exhibited enhanced charge separation, leading to an increased photocatalytic H2O2 production under visible light. This enhancement demonstrates the combined benefits of linker functionalization and stepwise protonation on photocatalytic efficiency.

Bimodal Oxidation Electrochemiluminescence Mechanism of Coreactant-Embedded Covalent Organic Frameworks via Postsynthetic Modification.

Electrochemiluminescence (ECL) efficiency is determined by charge transfer between coreactants and emitters in coreactant systems, which are usually limited by their slow intermolecular charge transfer. In this study, a covalent organic framework (COF) with aldehyde residue was synthesized, and then coreactants were covalently integrated into the skeleton through the postsynthetic modification strategy, resulting in a crystalline coreactant-embedded COF nanoemitter (C-COF). Compared to the pristine COF with an equivalent external coreactant, C-COF exhibited an extraordinary 1008-fold enhancement of ECL intensity due to the rapid intrareticular charge transfer. Significantly, with the pH increase, C-COF shows protonation-induced ECL enhancement for the first ECL peaked at +1.1 V and an opposite trend for the second ECL at +1.4 V, which were attributed to the antedating oxidation of coreactant in framework and COF self-oxidation, respectively. The resulting bimodal oxidation ECL mechanism was rationalized by spectral characterization and density functional theory calculations. The postsynthetic coreactant-embedded nanoemitters present innovative and universal avenues for advancing ECL systems.

Metagenomics and untargeted metabolomics analyses to unravel the formation mechanism of characteristic metabolites in Cantonese soy sauce during different fermentation stages.

Cantonese soy sauce (CSS) is an important Chinese condiment due to its distinctive flavor. Microorganisms play a significant role in the flavor formation of CSS during fermentation. However, the correlation between microbes and flavor compounds as well as the potential fermentation mechanism remained poorly uncovered. Here we revealed the dynamic changes of microbial structure and characteristics metabolites as well as their correlation of CSS during the fermentation process. Metagenomics sequencing analysis showed that Tetragenococcus halophilus, Weissella confusa, Weissella paramesenteroides, Aspergillus oryzae, Lactiplantibacillus plantarum, Weissella cibaria were top six dominant species from day 0 to day 120. Sixty compounds were either positively or tentatively identified through untargeted metabolomics profile and they were 27 peptides, amino acids and derivatives, 8 carbohydrates and conjugates, 14 organic acids and derivatives, 5 amide compounds, 3 flavonoids and 3 nucleosides. Spearman correlation coefficient indicated that Tetragenococcus halophilus, Zygosaccharomyces rouxii, Pediococcus pentosaceus and Aspergillus oryzae were significantly related with the formation of taste amino acids and derivatives, peptides and functional substances. Additionally, the metabolisms of flavor amino acids including 13 main free amino acids were also profiled. These results provided valuable information for the production practice in the soy sauce industry.

Ultrastable Anion Radicals in Ligand-Dimerized Frameworks for Self-Accumulated Electrochemiluminescence.

Electrochemiluminescence (ECL) is a light-emitting process that occurs via an annihilation reaction among energetic radical intermediates, whose stabilities determine the ECL efficiency. In this study, a ligand-dimerized metal-organic framework (MOF) with ultrastable anion radical is designed as an efficient nanoemitter for self-accumulated ECL. Due to the nonplanar structure of perylene diimide (PDI) derivate, two PDI ligands in the framework form a J-dimer unit with a vertical distance of ∼5.74 Å. In cathodic scanning, the ligand-dimerized MOF demonstrates three-step ECL emissions with a gradual increase in ECL intensity. Unlike the decrease in the PDI ligand, the self-accumulated ECL of the MOF was observed with 16.8-fold enhancement due to the excellent stability of radical intermediates in frameworks. Electron paramagnetic resonance demonstrated the ultrastability of free radicals in the designed frameworks, with 82.2% remaining even after one month of storage. Density functional theory calculations supported that PDI dimerization was energetically favorable upon successive electron injection. Moreover, the ECL wavelength is 610 nm, corresponding to the emission of excited dimers. The radical-stabilized reticular nanoemitters open up a new platform for decoding the fundamentals of self-accumulated ECL systems.

Sub-Second Electrochemiluminescence Imaging Assay of SARS-CoV-2 Nucleocapsid Protein Based on Reticulation of Endo-Coreactants.

The nonphotodriven electrochemiluminescence (ECL) imageology necessitates concentrated coreacting additives plus longtime exposures. Seeking biosafe and streamlined ensembles can help lower the bar for quality ECL bioimaging to which call the crystallized endo-coreaction in nanoreticula might provide a potent solution. Herein, an exo-coreactant-free ECL visualizer was fabricated out in one-pot, which densified the dyad triethylamine analogue: 1,4-diazabicyclo-[2.2.2]octane (DABCO) in the lamellar hive of 9,10-di(p-carboxyphenyl)anthracene (DPA)-Zn2+. This biligated non-noble metal-organic framework (m-MOF) facilitated a self-contained anodic ECL with a yield as much as 70% of Ru(bPy)32+ in blank phosphate buffered saline. Its featured two-stage emissions rendered an efficient and endurant CCD imaging at 1.0 V under mere 0.5 s swift snapshots and 0.1 s step-pulsed stimulation. Upon structural and spectral cause analyses as well as parametric set optimization, simplistic ECL-graphic immunoassay was mounted in the in situ imager to enact an ultrasensitive measurement of coronaviral N-protein in both signal-on and off modes by the privilege of straight surface amidation on m-MOFs, resulting in a wide dynamic range (10-4-10 ng/mL), a competent detection limit down to 56 fg/mL, along with nice precision and parallelism in human saliva tests. The overall work manifests a rudimentary endeavor in self-sufficient ECL visuality for brisk, biocompatible, and brilliant production of point-of-care diagnostic "Big Data".

Nanoconfined Cathodic Electrochemiluminescence for Self-Sensitized Bioimaging of Membrane Protein.

Self-enhanced electrochemiluminescence (ECL) can be achieved via the confinement of coreactants and ECL emitters in a single nanostructure. This strategy has been used for the design of anodic ECL systems with amine compounds as coreactants. In this work, a novel confinement system was proposed by codoping positively charged ECL emitter tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) and negatively charged coreactant peroxydisulfate (S2O82-) in silica nanoparticles. The codoping process could be performed by introducing S2O82- in cationic poly(diallyldimethylammonium chloride) (PDDA) to form PDDA@S2O82- and then encapsulating it and Ru(bpy)32+ in the Triton X-100 vesicle followed by the hydrolysis of tetraethyl ortosilicate, surface modification, and demulsification. The obtained RuSSNs exhibited good homogeneity, excellent monodispersity, acceptable biocompatibility, and 2.9-fold stronger ECL emission than Ru(bpy)32+-doped silica nanoparticles at an equal amount of nanoparticles in the presence of 0.1 M K2S2O8. Thus, an in situ self-sensitized cathodic ECL imaging method was designed for the monitoring of glycoprotein on living cell membranes. This work provides a new way for the modification, enhancement, and application of nano-ECL emitters in biological analysis.

Photocurrent Polarity Reversal Induced by Electron-Donor Release for the Highly Sensitive Photoelectrochemical Detection of Vascular Endothelial Growth Factor 165.

Photocurrent polarity reversal is a switching process between the anodic and cathodic pathways and is critical for eliminating false positivity and improving detection sensitivity in photoelectrochemical (PEC) sensing. In this study, we construct a PEC sensor with excellent photocurrent polarity reversal induced by ascorbic acid (AA) as an electron donor with the energy level matching the photoactive material zirconium metal-organic framework (ZrMOF). The ZrMOF-modified electrode demonstrates cathodic photocurrent in the presence of O2 as an electron acceptor, while the anodic photocurrent is generated in the presence of AA, achieving photocurrent polarity reversal. By the in situ release of AA from AA-encapsulated apoferritin modified with DNA 2 (AA@APO-S2) as a detection tag in the presence of trypsin after the recognition of hairpin DNA-modified indium tin oxide to the reaction product of aptamer/DNA 1 with the target protein and the following rolling cycle amplification for introducing the detection tag to the sensing interface, the reversed photocurrent shows an enhanced photocurrent response to the target protein, leading to a highly sensitive PEC sensing strategy. This strategy realizes the detection of vascular endothelial growth factor 165 with good specificity, a wide linear range, and a low detection limit down to 5.3 fM. The actual sample analysis offers the detection results of the proposed PEC sensor comparable to those of commercial enzyme-linked immunosorbent assay tests, indicating the promising application of the photocurrent polarity reversal-based PEC sensing strategy in biomolecule detection and clinical diagnosis.

Reticular Electrochemiluminescence Nanoemitters: Structural Design and Enhancement Mechanism.

ConspectusElectrochemiluminescence (ECL) is a powerful transduction technique, which depends critically on the formation of the excited emitter through the charge transfer between the electrochemical reaction intermediates of the emitter and the co-reactant/emitter. The exploration of ECL mechanisms for conventional nanoemitters is limited due to the uncontrollable charge transfer process. With the development of molecular nanocrystals, reticular structures such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been utilized as atomically precise semiconducting materials. The long-range order in crystalline frameworks and the tunable coupling among building blocks promote the quick development of electrically conductive frameworks. Especially, the reticular charge transfer can be regulated by both interlayer electron coupling and intralayer topology-templated conjugation. By modulating intramolecular or intermolecular charge mobility, reticular structures could serve as promising candidates for enhancing ECL. Thus, reticular crystalline nanoemitters with different topologies provide a confined platform to understand ECL fundamentals for designing next-generation ECL devices.Aiming at exploring the mechanism of ECL emission, our group has developed a series of ECL nanoemitters as well as enhancement strategies of ECL emission in the past 20 years. A series of water-soluble ligand-capped quantum dots were introduced as ECL nanoemitters to create sensitive analytical methods for detecting and tracing biomarkers. The functionalized polymer dots were also designed as ECL nanoemitters for imaging of membrane proteins with signal transduction strategies of dual resonance energy transfer and dual intramolecular electron transfer. To decode the ECL fundamental and enhancement mechanisms, an electroactive MOF with accurate molecular structure was first constructed with two redox ligands as a highly crystallized ECL nanoemitter in aqueous medium. Through the mixed-ligand approach, luminophores and co-reactants were integrated into one MOF structure for self-enhanced ECL. Furthermore, several donor-acceptor COFs were developed as efficient ECL nanoemitters with tunable intrareticular charge transfer. The atomically precise structure of conductive frameworks established clear correlations between the structure and charge transport in these materials. Therefore, reticular materials as crystalline ECL nanoemitters have demonstrated both proof of concept and mechanistic innovation.In this Account, taking advantage of reticular materials with accurate molecular structure, we survey the design of the electroactive reticular materials including MOFs and COFs as crystalline ECL nanoemitters at the molecular level. The enhancement mechanisms of ECL emission of various topology frameworks are discussed via the regulation of reticular energy transfer and charge transfer and the accumulation of anion/cation radicals. Our perspective on the reticular ECL nanoemitters is also discussed. This Account provides a new avenue for designing molecular crystalline ECL nanoemitters and decoding the fundamentals of ECL detection methods.

A Versatile G-Quadruplex (G4)-Coated Upconverted Metal-Organic Framework for Hypoxic Tumor Therapy.

Given the complexity of the tumor microenvironment, multiple strategies are being explored to tackle hypoxic tumors. The most efficient strategies combine several therapeutic modalities and typically requires the development of multifunctional nanocomposites through sophisticated synthetic procedures. Herein, the G-quadruplex (G4)-forming sequence AS1411-A (d[(G2 T)4 TG(TG2 )4 A]) is used for both its anti-tumor and biocatalytic properties when combined with hemin, increasing the production of O2 ca. two-fold as compared to the parent AS1411 sequence. The AS1411-A/hemin complex (GH) is grafted on the surface and pores of a core-shell upconverted metal-organic framework (UMOF) to generate a UMGH nanoplatform. Compared with UMOF, UMGH exhibits enhanced colloidal stability, increased tumor cell targeting and improved O2 production (8.5-fold) in situ. When irradiated by near-infrared (NIR) light, the UMGH antitumor properties are bolstered by photodynamic therapy (PDT), thanks to its ability to convert O2 into singlet oxygen (1 O2 ). Combined with the antiproliferative activity of AS1411-A, this novel approach lays the foundation for a new type of G4-based nanomedicine.

Postsynthetic Annulation of Three-Dimensional Covalent Organic Frameworks for Boosting CO2 Photoreduction.

Three-dimensional covalent organic frameworks (3D COFs), with interconnected pores and exposed functional groups, provide new opportunities for the design of advanced functional materials through postsynthetic modification. Herein, we demonstrate the successful postsynthetic annulation of 3D COFs to construct efficient CO2 reduction photocatalysts. Two 3D COFs, NJU-318 and NJU-319Fe, were initially constructed by connecting hexaphenyl-triphenylene units with pyrene- or Fe-porphyrin-based linkers. Subsequently, the hexaphenyl-triphenylene moieties within the COFs were postsynthetically transformed into π-conjugated hexabenzo-trinaphthylene (pNJU-318 and pNJU-319Fe) to enhance visible light absorption and CO2 photoreduction activity. The optimized photocatalyst, pNJU-319Fe, shows a CO yield of 688 µmol g-1, representing a 2.5-fold increase compared to that of unmodified NJU-319Fe. Notably, the direct synthesis of hexabenzo-trinaphthylene-based COF catalysts was unsuccessful due to the low solubility of conjugated linkers. This study not only provides an effective method to construct photocatalysts but also highlights the unlimited tunability of 3D COFs through structural design and postsynthetic modification.

Gold Microbeads Enabled Proximity Electrochemiluminescence for Highly Sensitive and Size-Encoded Multiplex Immunoassays.

Developing highly sensitive multiplex immunoassays is urgently needed to guide medical research and improve clinical diagnosis. Here, we report the proximity electrochemiluminescence (ECL) generation enabled by gold microbeads (GMBs) for improving the detection sensitivity and multiplexing capacity of ECL immunoassays (ECLIAs). As demonstrated by microscopy and finite element simulation, GMBs can function as spherical ultramicroelectrodes for triggering ECL reactions in solutions. Employing GMBs as solid carriers in the bead-based ECLIA, the electrochemical oxidation of a coreactant can occur at both the GMB surface and the substrate electrode, allowing the coreactant radicals to diffuse only a short distance of ∼100 nm to react with ECL luminophores that are labeled on the GMB surface. The ECL generation via this proximity low oxidation potential (LOP) route results in a 21.7-fold increase in the turnover frequency of ECL generation compared with the non-conductive microbeads that rely exclusively on the conventional LOP route. Moreover, the proximity ECL generation is not restricted by the diffusion distance of short-lived coreactant radicals, which enables the simultaneous determination of multiple acute myocardial infarction biomarkers using size-encoded GMB-based multiplex ECLIAs. This work brings new insight into the understanding of ECL mechanisms and may advance the practical use of multiplex ECLIAs.

A Self-Templated Design Approach toward Multivariate Metal-Organic Frameworks for Enhanced Oxygen Evolution.

Multivariate metal-organic framework (MOF) is an ideal electrocatalytic material due to the synergistic effect of multiple metal active sites. In this study, a series of ternary M-NiMOF (M = Co, Cu) through a simple self-templated strategy that the Co/Cu MOF isomorphically grows in situ on the surface of NiMOF is designed. Owing to the electron rearrange of adjacent metals, the ternary CoCu-NiMOFs demonstrate the improved intrinsic electrocatalytic activity. At optimized conditions, the ternary Co3 Cu-Ni2 MOFs nanosheets give the excellent oxygen evolution reaction (OER) performance of current density of 10 mA cm-2 at low overpotential of 288 mV with a Tafel slope of 87 mV dec-1 , which is superior to that of bimetallic nanosheet and ternary microflowers. The low free energy change of potential-determining step identifies that the OER process is favorable at Cu-Co concerted sites along with strong synergistic effect of Ni nodes. Partially oxidized metal sites also reduce the electron density, thus accelerating the OER catalytic rate. The self-templated strategy provides a universal tool to design multivariate MOF electrocatalysts for highly efficient energy transduction.

Electron Donor Coordinated Metal-Organic Framework to Enhance Photoelectrochemical Performance.

To enhance photoelectrochemical (PEC) performance, additional electron donor/acceptor is generally required to inhibit the electron-hole recombination. However, the enhancement is limited due to the long-distance diffusion. Herein a self-supplying electron strategy is designed for PEC enhancement by coordinating an electron donor 1.4-diazabicyclo[2.2.2]octane (Dabco) in metal-organic framework (MOF). The intrareticular photoelectron transfer mechanism in mixed-ligand MOF (m-MOF) is experimentally revealed and verified by density functional theory calculations. The presence of Dabco efficiently inhibits the electron-hole recombination due to the self-supplying electrons and longer electron lifetime in the framework, and thus leads to 23.2-fold enhancement of photocurrent. As proof of concept, a simple PEC method is constructed with the designed m-MOF to demonstrate its application in sensitive bioanalysis. This work provides a new avenue for improving the PEC performance of nanomaterials.

Photothermal-Responsive Intelligent Hybrid of Hierarchical Carbon Nanocages Encapsulated by Metal-Organic Hydrogels for Sensitized Photothermal Therapy.

Hierarchical carbon nanocages as emerging nanomaterials have a great potential for photothermal therapy due to their unique porous structure, high specific surface area, and excellent photothermal property. Herein, a hierarchical nitrogen-doped carbon nanocage (hNCNC) is introduced as a second near-infrared photothermal agent, and then functionalizes it with metal-organic hydrogel (MOG) to form a thermal-responsive switch for sensitized photothermal therapy. Upon 1064 nm light irradiation, the hNCNCs exhibit a remarkable photothermal conversion efficiency of 65.9% owing to a high near-infrared extinction coefficient. Meanwhile, due to the hierarchical structure, hNCNCs show 60.2% (wt./wt.) loading efficiency of quercetin, a heat shock protein (Hsp70) inhibitor. Through thermal-driven dry-gel transformation, the coating MOGs intelligently release the encapsulated quercetin for sensitizing cancer cells to heat. Based on the synergistic effect of hyperthermia elevation and thermal-driven drug release, the dual thermal utilization platform achieves effective photothermal tumor ablation in vivo under low concentration of hNCNCs and mild irradiation, which provides a new diagram of intelligent responsive photothermal agents for enhanced photothermal therapy.

In situ coordination interactions between metal-organic framework nanoemitters and coreactants for enhanced electrochemiluminescence in biosensing.

Coreactant electrochemiluminescence (ECL) is one of the most popular pathways in commercial analysis, which can provide simplicity and convenience for getting intense ECL emission. However, the low efficiency of intermolecular electron transfer could weaken ECL intensity. In this work, we developed an enhanced ECL strategy through in situ coordination interactions between metal-organic framework emitters and coreactants. First, a metal-organic framework (MOF) emitter was synthesized with 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane (TPPE) as aggregation-induced emission linkers and Zn as nodes. Interestingly, compared to TPPE ligand, the resulted MOF nanoemitters demonstrated 49.5 folds enhancement of ECL emission in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as the coreactant. More significantly, different from the constant ECL intensity using TPrA coreactant, DABCO exhibited time-dependent ECL intensity due to the intrareticular electron transfer through coordination interaction between DABCO and Zn2+, which was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectral experiments. The enhanced ECL was then applied to construct a sensitive ECL method to detect dopamine in serum samples. The coordination interaction between emitters and coreactants not only provides a universal way to enhance ECL, but also expands the applications of coreactant ECL system in convenience route.

A Double Hemin Bonded G-Quadruplex Embedded in Metal-Organic Frameworks for Biomimetic Cascade Reaction.

Biocatalytic transformations in living cells, such as enzymatic cascades, function effectively in spatially confined microenvironments. However, mimicking enzyme catalytic cascade processes is challenging. Herein, we report a new dual-Hemin-G-quadruplex (dHemin-G4) DNAzyme with high catalytic activity over noncovalent G4/Hemin and monocovalent counterparts (G4-Hemin and Hemin-G4) by covalently linking hemin to both ends of an intramolecular G4. We use MAF-7, a hydrophilic metal-organic framework (MOF), as the protecting scaffold to integrate a biocatalytic cascade consisting of dHemin-G4 DNAzyme and glucose oxidase (GOx), by a simple and mild method with a single-step encapsulation of both enzymes. Such a MAF-7-confined cascade system shows superior activity over not only traditional G4/Hemin but also other MOFs (ZIF-8 and ZIF-90), which was mainly attributed to high-payload enzyme packaging. Notably, the introduction of hydrophilic G4 allows to avoid the accumulation of hydrophobic hemin on the surface of MAF-7, which decreases cascade biocatalytic activity. Furthermore, MAF-7 as protective coatings endowed the enzyme with excellent recyclability and good operational stability in harsh environments, including elevated temperature, urea, protease, and organic solvents, extending its practical application in biocatalysis. In addition, the incorporated enzymes can be replaced on demand to broaden the scope of catalytic substrates. Taking advantages of these features, the feasibility of dHemin-G4/GOx@MAF-7 systems for biosensing was demonstrated. This study is conducive to devise efficient and stable enzyme catalytic cascades to facilitate applications in biosensing and industrial processes.

BODIPY-based metal-organic frameworks as efficient electrochemiluminescence emitters for telomerase detection.

A boron dipyrromethene (BODIPY)-based metal-organic framework (MOF) nanoemitter was for the first time designed with enhanced electrochemiluminescence (ECL) intensity due to the suppression of non-radiative dissipation originating from the ordered arrangement of BODIPY molecules in the framework. Thus, an ECL biosensor was developed for telomerase detection with excellent performance in real samples.

Efficient Biocatalytic System for Biosensing by Combining Metal-Organic Framework (MOF)-Based Nanozymes and G-Quadruplex (G4)-DNAzymes.

A high catalytic efficiency associated with a robust chemical structure are among the ultimate goals when developing new biocatalytic systems for biosensing applications. To get ever closer to these goals, we report here on a combination of metal-organic framework (MOF)-based nanozymes and a G-quadruplex (G4)-based catalytic system known as G4-DNAzyme. This approach aims at combining the advantages of both partners (chiefly, the robustness of the former and the modularity of the latter). To this end, we used MIL-53(Fe) MOF and linked it covalently to a G4-forming sequence (F3TC), itself covalently linked to its cofactor hemin. The resulting complex (referred to as MIL-53(Fe)/G4-hemin) exhibited exquisite peroxidase-mimicking oxidation activity and an excellent robustness (being stored in water for weeks). These properties were exploited to devise a new biosensing system based on a cascade of reactions catalyzed by the nanozyme (ABTS oxidation) and an enzyme, the alkaline phosphatase (or ALP, ascorbic acid 2-phosphate dephosphorylation). The product of the latter poisoning the former, we thus designed a biosensor for ALP (a marker of bone diseases and cancers), with a very low limit of detection (LOD, 0.02 U L-1), which is operative in human plasma samples.

Glutathione-Responsive Heterogeneous Metal-Organic Framework Hybrids for Photodynamic-Gene Synergetic Cell Apoptosis.

A core-shell heterogeneous metal-organic framework (MOF) hybrid is sequentially designed by a photosensitized porous coordination network (PCN)-typed MOF as core and Cu2+ -centered zeolitic imidazolate framework (ZIF-67) as shell encapsulating cyanine 3-labelled siRNA. The heterogeneous MOF hybrid realized stimulus-responsive photodynamic therapy (PDT) and controllable siRNA delivery through 1 O2 -assistant endosomal escape for imaging-guided photodynamic-gene synergetic theranostics.

Nonenzymatic Target-Driven DNA Nanomachine for Monitoring Malathion Contamination in Living Cells and Bioaccumulation in Foods.

Intensive applications of toxic malathion pesticides bring a vital threat to the environment and health. Hence, a credible and sensitive strategy is urgently needed for the respective detection of malathion. In this work, an aptamer-based nonenzymatic autonomous DNA walking machine was fabricated for monitoring trace malathion contamination in cells and foods. Along with the machine walking driven by malathion-triggered reaction entropy, multiple fluorescent signal outputs were thermodynamically generated for signal amplification. The proposed stable DNA nanomachine achieved satisfactory results with a detection limit of 81.9 pg L-1 for testing malathion, which could be applied to actual samples including apple juice, paddy water, and paddy soil. Furthermore, the high stability, sensitivity, and biocompatibility of the nanomachine enabled monitoring of the malathion contamination in living cells and bioaccumulation in lettuce without additional purification. Consequently, with these excellent performances, it is strongly anticipated that the DNA walking machine has tremendous potential to be extended to general platforms against pesticides to avoid malathion-contaminated agricultural production for environmental safety and human health.