Displacement Reaction Research Articles

A Dual-Mode Colorimetric and Fluorescence Biosensor Based on a Nucleic Acid Multiplexing Platform for the Detection of Listeria monocytogenes.

Listeria monocytogenes (L. monocytogenes) is one of the most prevalent threats, capable of inducing diverse illnesses and presenting a serious threat to public health. Herein, we demonstrate a novel dual-mode colorimetric/fluorescence biosensor based on the exponential amplification reaction and strand displacement reactions (EASDR), which has multiplexing capability that significantly promotes the anchoring and trapping of Pt nanoparticles (Pt NPs) and fluorescent dyes for sensitive detection of Listeria monocytogenes (L. monocytogenes). The method works by targeting specific bacteria with aptamers and promoting repeated EASDR to affect the immobilization of Pt NPs and fluorescent dyes in the orifice plate, which could produce changes in fluorescence and colorimetric signals. The assay achieves a detection limit of 38 CFU/mL in colorimetric and 10 CFU/mL in fluorescence. Furthermore, the developed biosensor can be applied to the analysis of raw food samples (milk), and good recoveries were obtained in spiked food samples. In summary, the dual-mode biosensor improves the accuracy of detection by simultaneously outputting two signals and shows great potential in the specific identification and detection of foodborne pathogens.

The Evolution of Nucleic Acid Nanotechnology: From DNA Assembly to DNA-Encoded Library.

Deoxyribonucleic acid (DNA), a fundamental biomacromolecule in living organisms, serves as the carrier of genetic information. Beyond its role in encoding biological functions, DNA's inherent ability to hybridize through base pairing has opened new avenues for its application in biological sciences. This review introduces DNA nanotechnology and DNA-encoded library (DEL), and highlights their shared design principles related to DNA assembly. First, a foundational overview of structural DNA nanotechnology, including its design strategies and historical development is provided. Subsequently, various approaches are examined to dynamic DNA nanotechnology, from strand displacement reactions to DNA-templated polymer synthesis. Second, how the principle of DNA assembly has facilitated the development of diverse formats of self-assembly-based DEL synthesis, DNA-template reactions (DTS), and DNA template-mediated proximity induction effects are examined. These advancements are all underpinned by the unique property of DNA assembly. Finally, this review summarizes the common principles shared by DNA nanotechnology and DEL in terms of methodology and design. Additionally, the potential synergies are explored between these two technologies, envisioning future applications where they can be combined to create more versatile and exquisite functionalities.

Thrombin Nanochannel Logic Gate Inspired by BioMemory.

The process of "reading" and "writing" in biomemory involves the transmission of electrical signals between neurons, with ligand-gated ion channels assuming a key role. The solid-state nanochannels exhibit certain similarities with neurons. Information transmission can be achieved by controlling the flow of ions within nanochannels, rendering them potentially suitable for simulating neuron behavior. Herein, thrombin (Thr) was chosen as the target protein, and a functionalized nanochannel sensing system was successfully constructed using DNA aptamers, enabling a highly sensitive Thr response with a detection limit of 0.221 fM. Simultaneously, based on Watson-Crick base pairing and programmable chain displacement reactions, controlled release and cyclic response of the target molecule were further achieved. This mechanism elucidates the rules governing specific input-output relationships, innovatively linking them with memory storage and recognition through the Thr-nanochannel logic gate, thereby realizing the reading of biomemory at the hardware level. In summary, the biological hybrid nanofluidic control device of this invention converts molecular events into electrical signals, providing potential avenues for establishing connections between the mechanisms of biomemory and solid-state nanochannel biosensing and recognition in the future.

Enhanced Drilling Waste-Water Treatment through Magnetic Nano-Composite Coagulant Application: A Central Composite Design Study

A magnetic nano-composite coagulant has been designed, originally applied in a specific industrial waste-water treatment, and statistically investigated using Central Composite Design (CCD). The generated polynomial models were utilized to achieve a comprehensive understanding of the impact of each ingredient of PolyAluminum Chloride (PAC), PolyAcrylAmide (PAM), and Iron (III) oxide magnetic nano particles (MNP) regarding optimum limits and conditions. The concentration of each of those components has been considered as the main effective factors, which are found to be significantly correlated, affecting the Total Dissolved Solid (TDS) removal (%), the Total Suspended Solid (TSS) removal (%), and the Turbidity Reduction Rate (TRR) NTU/min. The reliable statistical model for each response underscored the pivotal role of MNP in shaping each response variable. The influence of MNP and PAC, emerged as crucial in enhancing TDS removal, by increasing the kinetic energy of charged ions and the chance of the successful displacement reaction, helping to dissolve with a high surface activity, and the adsorption of magnetic heavy ions. The correlated concentration of MNP also exhibited a significant impact on TSS elimination, and TRR, concurrently, which revealed the importance of controlling the bulk density of generated flocs, to prevent premature and immature settling to optimize pollution removal. The highest recorded results are 72.00%, 77.01%, and 23.82 NTU per minute for TDS and TSS removal and TRR, respectively. The experimental records, along with the statistical investigation remarked a promising potential of the achieved Magnetic Nano-composite Coagulant (MNC), and generated practical knowledge of its novel application for drilling waste-water management.

Quantitative Analysis of the Effect of Fluorescent Labels on DNA Strand Displacement Reaction.

DNA chemical reaction networks can perform complex information processing through careful design of reaction kinetics, which involves the reaction network structure, rate constants, and initial concentrations. The toehold-mediated strand displacement reaction (TMSDR) is a key mechanism in creating DNA circuits, offering a rational design approach by integrating individually designed TMSDRs. Tools such as VisualDSD and NUPACK facilitate the efficient design of these systems by allowing precise tuning of reaction parameters. However, discrepancies between simulated and experimental results can occur, often due to the modification of reporter molecules. Recently, fluorophore dyes and quenchers were found to significantly impact the dynamics of irreversible TMSDRs, altering them by nearly two orders of magnitude. The impact on reaction dynamics varies with the modification site of these reporters. This study examines the mechanisms of reporter modifications affecting reversible TMSDRs, influencing transient and steady-state characteristics. This is crucial for DNA circuit design, which integrates reversible and irreversible TMSDRs. Our findings indicate that modifying fluorescent dye and quencher an appropriate distance apart (e.g., toehold length) can minimize adverse effects on the DNA reaction dynamics while ensuring effective FRET, therefore improving the accuracy of experimental verification for DNA reaction systems.

Enhanced Durability of Zn-Metal Anodes through in-Situ Bi-Layer Coating with Metal Fluoride and Polymer

Aqueous Zn metal batteries (AZBs) have garnered considerable attention in the quest for safer, more sustainable energy storage solutions, primarily due to their inherent non-flammability and cost-effectiveness. However, the commercial deployment of AZBs has been hindered by two major challenges: the growth of Zn dendrites and the parasitic hydrogen evolution reaction (HER) at the Zn metal anodes (ZMAs). These phenomena compromise battery safety and efficiency, thereby limiting their practical applications. To address these issues, this study introduces a novel bi-layered Zn protective layer (BSPL@Zn), fabricated through a one-step in-situ coating process. This protection strategy employs a polyvinyl(alcohol), hydrophilic polymeric outer layer coupled with a zincophilic, Ag-decorated inner layer (Ag0/ZnF2), created by an in-situ displacement reaction facilitated by a silver fluoride (AgF) additive.The innovative aspect of BSPL@Zn lies in its dual functionality. The Ag-decorated inner layer is specifically engineered to be zincophilic, promoting homogeneous Zn deposition, while the hydrophilic polymer outer layer effectively suppresses the HER. This configuration not only mitigates the formation of dendritic structures but also significantly reduces the rate of hydrogen gas evolution—a common issue that exacerbates anode degradation and battery failure. Experimental results demonstrate that the BSPL@Zn successfully extends the short-circuiting time of the batteries, achieving a three-fold reduction in H2 gas evolution compared to conventional ZMA systems.Further evaluations in Zn||Zn symmetric cells reveal that BSPL@Zn enables robust cycling performance, sustaining over 1800 hours at a Zn plating capacity of 5 mAh cm−2. When implemented in Zn||NH4V4O10 cells, BSPL@Zn maintains stable battery operation across 1000 cycles with an impressive 80% capacity retention. These findings underscore the effectiveness of the bi-layer approach in enhancing the durability and operational stability of AZBs.This study not only elucidates the mechanisms by which BSPL@Zn enhances the performance and safety of AZBs but also highlights the importance of material selection and strategic design in anode protection. By integrating zincophilic and hydrophilic properties within a single protective structure, this work paves the way for future advancements in battery technology. The development of such tailored protective coatings could significantly propel the commercial viability of AZBs, promoting their wider adoption in various applications demanding high safety and efficiency standards.

Structure-engineered tellurium for enhancing H2S gas sensing properties at room temperature

Tellurium nanostructures were utilized as a gas sensing material to detect hydrogen sulfide gases at room temperature. Te nanostructures were synthesized by a galvanic displacement reaction of nickel particles as a sacrificial material. The morphologies of Te hollow spheres and branched Te hollow spheres were controlled by the concentration of the employed HTeO2+. The branched Te hollow spheres were formed by additional nucleation and growth of Te branches on the surface of Te hollow sphere in high concentration of HTeO2+. Compared to the room temperature sensing properties of Te hollow spheres, the branched Te hollow spheres showed the significantly enhanced sensitivity. The improved performance in the branched Te hollow spheres is attributed to the increased specific surface area, larger variation of hole accumulation layer for carrier transport, and especially drastic variation of electrical resistance in the increased junction potentials between the branches. Additionally, the branched Te hollow spheres showed strong selectivity for H2S over other gases such as NO2, SO2, and H2, making them highly effective for detecting H2S at room temperature.

Spatial Control over Reactions via Localized Transcription within Membraneless DNA Nanostar Droplets.

Biomolecular condensates control where and how fast many chemical reactions occur in cells by partitioning reactants and catalysts, enabling simultaneous reactions in different spatial locations of a cell. Even without a membrane or physical barrier, the partitioning of the reactants can affect the rates of downstream reaction cascades in ways that depend on reaction location. Such effects can enable systems of biomolecular condensates to spatiotemporally orchestrate chemical reaction networks in cells to facilitate complex behaviors such as ribosome assembly. Here, we develop a system for developing such control in synthetic systems. We localize different transcription templates within different phase-separated, membraneless DNA nanostar (NS) droplets─programmable, in vitro liquid-liquid phase separation systems for partitioning of substrates and localization of reactions to membraneless droplets. When RNA produced within such droplets is also degraded in the bulk, droplet-localized transcription creates RNA concentration gradients. Consistent with the formation of these gradients, toehold-mediated strand displacement reactions involving transcripts are 2-fold slower far from the site of transcription than when nearby. We then demonstrate how multiple such gradients can form and be maintained independently by simultaneous transcription reactions occurring in tandem, each localized to different NS droplet types. Our results provide a means for constructing reaction systems in which different reactions are spatially localized and controlled without the need for physical membranes. This system also provides a means for generally studying how localized reactions and the exchange of reaction products might occur between protocells.

Stereoview Images of Hydrogen-Bonded Quinoxalines with a Helical Axis; Pyrimidines and a Pyridazine That Form Extended Tapes.

Different supramolecular motifs are formed by the crystallisation of amino-substituted derivatives of quinoxaline, pyrimidine and pyridazine. These were made from the corresponding mono- or dichlorinated heterocycles by a nucleophilic displacement reaction. The pyridine-type nitrogen atoms activate the chlorine atoms because they can stabilise a negative charge, which forms when the amine attacks the ring. One amino group can be attached under mild conditions in hot ethanol or acetonitrile, but the first then deactivates the ring so the second requires more forceful conditions using a pressure vessel at 150 °C. Butylamine is frequently used because it reduces the polarity of the product, making it easier to purify and isolate. The extended structure of the quinoxaline derivatives 16-18 show a common 'pincer' hydrogen-bond motif, with a quinoxaline nitrogen atom accepting two N-H···N hydrogen bonds, giving a spiral or helical axis. The chain symmetries are 41, 21 and 31, respectively, depending on the substituents. A stereoview of each is shown. The pyrimidine derivatives 19, 12, 20, 14 and 21 form hydrogen-bonded tapes and compound 20 forms inversion dimers.

A rapid dual-mode SERS/FL cytosensor assisted via DNA Walker-based plasmonic nanostructures

Various surface-enhanced Raman scattering (SERS) biosensors offer powerful tools for the ultrasensitive detection of circulating tumor cells (CTCs) and tumor diagnosis. Despite their efficacy, the swift and precise preparation of SERS plasmonic nanostructures poses an ongoing challenge. In this study, we introduce DNA-assisted plasmonic nanostructures capable of producing dual signals and facilitating DNA Walker signal amplification, resulting in the development of a SERS/Fluorescent (FL) dual-mode cytosensor for CTCs detection. Firstly, Au@Ag nanoparticle multimers (Au@AgNMs) featuring interparticle nano-gaps were synthesized through DNA self-assembly and in-situ deposition, which provided plasmonic nanostructures. Hence, the nano-gap distance among Au@AgNMs was meticulously regulated after optimization to achieve both SERS enhancement and fluorescence quenching. Subsequently, the aptamer (Apt) of MUC1 recognized CTCs specifically for strand displacement reaction (SDR) and further triggered the DNA Walker reaction for signal amplification. The limit of detection (LOD) of proposed cytosensor can be obtained as low as 5 cells/mL in SERS mode and 21 cells/mL in FL mode. Hence, SERS mode confers highly precise information, while FL mode allow for rapid quantitative analysis. This dual-mode cytosensor based on plasmonic nanostructures facilitates the early detection and precise treatment of cancer or infectious diseases.

Flexible Fluorine-Thiol Displacement Stapled Peptides with Enhanced Membrane Penetration for the Estrogen Receptor/Coactivator Interaction

Understanding how natural and engineered peptides enter cells would facilitate the elucidation of biochemical mechanisms underlying cell biology and is pivotal for developing effective intracellular targeting strategies. In this study, we demonstrate that our peptide stapling technique, fluorine-thiol displacement reaction (FTDR), can produce flexibly constrained peptides with significantly improved cellular uptake, particularly into the nucleus. This platform confers enhanced flexibility, which is further amplified by the inclusion of a D amino acid, while maintaining environment-dependent α helicity, resulting in highly permeable peptides without the need for additional cell-penetrating motifs. Targeting the ERα-coactivator interaction prevalent in estrogen receptor-positive (ER+) breast cancers, we showcased that FTDR-stapled peptides, notably SRC2-LD, achieved superior internalization, including cytoplasmic and enriched nuclear uptake, compared to peptides stapled by ring-closing metathesis (RCM). These FTDR-stapled peptides utilize different mechanisms of cellular uptake, including energy-dependent transport such as actin-mediated endocytosis and macropinocytosis. As a result, FTDR peptides exhibit enhanced anti-proliferative effects despite their slightly decreased target affinity. Our findings challenge existing perceptions of cell permeability, emphasizing the possibly incomplete understanding of the structural determinants vital for cellular uptake of peptide-like macromolecules. Notably, while α helicity and lipophilicity are positive indicators, they alone are insufficient to determine high cell permeability, as evidenced by our less helical, more flexible, and less lipophilic FTDR-stapled peptides.

Highly Active NiRu/C Cathode Catalyst Synthesized by Displacement Reaction for Anion Exchange Membrane Water Electrolysis.

Anion exchange membrane water electrolysis (AEMWE) is highly promising for cost-effective green hydrogen production due to its basic operating conditions facilitating the use of non-noble catalysts. While non-noble Ni/Fe-based catalysts are utilized at the anode, its cathode catalyst still requires precious Pt. Due to the high cost of Pt and the sluggish hydrogen evolution reaction (HER) at the cathode in basic conditions, developing alternative catalysts to replace Pt is highly important. Here, a synthesis procedure for a Ru-based catalyst is reported and its high activity toward the HER in alkaline media is demonstrated in both half-cell and single-cell tests. The catalyst is synthesized in a two-step approach. A highly dispersed Ni catalyst is prepared on carbon support in the first step. In the second step, Ru is deposited on its surface using a galvanic displacement reaction. The uniqueness of this method is that Ru is deposited over the entire electrically conductive surface, resulting in an isotropic and homogeneous Ru distribution within the catalyst powder. It is demonstrated that this material remarkably outperforms state-of-the-art Pt/C catalysts in half-cell and single-cell tests. The single cell only requires 1.73V at 1A cm-2 with an overall PGM content of 0.05mg cm-2.

Crystallographic Dimensionality Determines the Electrochemical Reaction Mechanism in Alkali Transition-Metal Chlorides.

Intense research efforts on transition metal chalcogenides (oxides and sulfides), pnictides (nitrides and phosphides), and fluorides have demonstrated the complex, intertwined effects of structural and chemical changes on their electrochemical response leading to intercalation, conversion, or displacement reactions when reacting with lithium. Prior efforts largely left halides unexplored due to their heightened solubility in classical liquid electrolytes. In this work, we employ superconcentrated electrolytes to demonstrate the composition- and structure-dependent electrochemical reactivity of A2MCl4 compounds (A = Li or Na and M = Cr, Mn, Fe, and Co). Comparing four lithiated compounds, we demonstrate that they all undergo conversion reactions when reacting with 2 Li+ per formula unit, associated with large polarization and limited cycling ability. Nevertheless, combining in situ XRD with post-mortem XPS and STEM/EDS analysis, we demonstrate that Li2CoCl4 first reacts with one Li+ following a displacement reaction providing a reversible capacity of 125 mAh g-1. This reaction is enabled by the formation of a Li6CoCl8 intermediate, which shares a similar anionic framework with pristine Li2CoCl4, ensuring the topotactic insertion of Li+ balanced by the Co2+/Co0 redox couple and the formation of metallic Co nanoparticles. Comparing these compounds, we propose that two criteria are necessary to trigger the displacement reaction in A2MCl4 compounds: the presence of 1D chains of edge-sharing octahedra to favor electronic delocalization and the availability of a metal-deficient intermediate. Screening numerous A2MCl4 compounds, we demonstrate the universality of these design principles, which extend to Na-ion materials by demonstrating a low-polarization, reversible displacement reaction for Na2MnCl4.

Study on the Factors Influencing the Adsorption Mechanism of CSH Gel for Chloride Ions.

Calcium silicate hydrate (CSH) gel is an important hydration product of cement, significantly influencing the coagulation and hardening processes, as well as the mechanical properties, volume stability, and durability of cement. Moreover, it plays a crucial role in the adsorption of harmful ions. In this study, CSH gel was synthesized through the precipitation of calcium acetate and sodium silicate and was subsequently used to adsorb chloride ions. The results indicated that when the calcium-to-silicon ratio was 1.2, the CSH gel exhibited excellent adsorption performance for chloride ions introduced via CaCl2 and NaCl, with adsorption capacities of 17.45 mg·g-1 and 8.06 mg·g-1, respectively. The adsorption of chloride ions in CSH gel primarily occurs due to the physical adsorption of chloride ions on the surface and within the internal pores of the CSH gel, accompanied by a displacement reaction between hydroxide ion and chloride ions.

Dissociation Constant (Kd) Measurement for Small-Molecule Binding Aptamers: Homogeneous Assay Methods and Critical Evaluations.

Since 1990, numerous aptamers have been isolated and discovered for use in various analytical, biomedical, and environmental applications. This trend continues to date. A critical step in the characterization of aptamer binding is to measure its binding affinity toward both target and non-target molecules. Dissociation constant (Kd) is the most commonly used value in characterizing aptamer binding. In this article, homogenous assays are reviewed for aptamers that can bind small-molecule targets. The reviewed methods include label-free methods, such as isothermal titration calorimetry, intrinsic fluorescence of target molecules, DNA staining dyes, and nuclease digestion assays, and labeled methods, such as the strand displacement reaction. Some methods are not recommended, such as those based on the aggregation of gold nanoparticles and the desorption of fluorophore-labeled DNA from nanomaterials. The difference between the measured apparent Kd and the true Kd of aptamer binding is stressed. In addition, avoiding the titration regime and paying attention to the time required to reach equilibrium are discussed. Finally, it is important to include mutated non-binding sequences as controls.

Chalcogen Bond-Driven Alkylations: Selenoxide-Pillar[5]arene as a Recyclable Catalyst for Displacement Reactions in Water.

A novel strategy to catalyze alkylation reactions through chalcogen bond interaction using a supramolecular structure is presented herein. Utilizing just 1.0 mol % of selenoxide-pillar[5]arene (P[5]SeO) as the catalyst we achieved efficient catalysis in the cyanation of benzyl bromide in water. Our approach demonstrated high efficiency and effectiveness, with the results supported by designed control experiments and theoretical models, highlighting the catalytic effect of the pillar[5]arene through noncovalent interactions. Quantum-chemical calculations (ωB97X-D/def2-TZVP@SMD) pointed out that the catalyzed cyanation reaction followed an SN2-like mechanism, with energy barriers (ΔH≠) ranging from 16.7 to 18.2 kcal mol-1, exhibiting dissociative character depending on the para-substituent. 1H NMR analysis revealed that P[5]SeO acted as a catalyst through inclusion complex formation, facilitating the transfer of the electrophilic substrate to the aqueous solution for nucleophilic displacement. Our reaction protocol proved applicable to various substrates, including aromatic and alpha-carbonyl derivatives. The use of sodium azide as the nucleophile was also feasible. Importantly, our method allowed scalability, and the catalyst P[5]SeO could be recovered and reused effectively for multiple reaction cycles, showcasing sustainability.

Close Proximity of Cholesterol Anchors in Membrane Induces the Dissociation of Amphiphilic DNA Strand from Membrane Surface.

Dynamic DNA nanotechnology is appealing for membrane surface engineering due to their versatility and programmability. To modulate the dynamic interactions between the DNA functional units immobilized on membrane surface, membrane-anchored DNA functional units often come into close proximity each other due to DNA base pairing, which also leads to the close contact of the hydrophobic anchors in membrane. However, whether the close contact of hydrophobic anchors induces the dissociation of amphiphilic DNA structures from membrane surface is not concerned. Herein, we utilized cholesterol-labelled single-stranded DNA (ssDNA) as a simplified amphiphilic DNA structure to investigate the stability of membrane anchored DNA strands upon the closely contact of cholesterol anchors. The close contact of cholesterol-labelled ssDNA molecules driven by toehold mediated strand displacement reaction leads to approximately 41 % membrane anchored ssDNA dissociation from membrane surface, indicating the proximal cholesterol anchors in membrane could reduce the anchoring stability of cholesterol-modified DNA strands. This work enhances our understanding of the interactions between amphiphilic DNA and membranes, and provides valuable insights for the design of future DNA constructs intended for applications involving dynamic DNA reactions on membrane surface.

Construction of an efficient microRNA sensing platform based on terminal deoxynucleotidyl transferase-mediated synthesis of copper nanoclusters

A conceptual innovative electrochemical sensing platform was constructed for microRNA (miRNA) detection based on terminal deoxynucleotidyl transferase (TdT)-mediated synthesis of copper nanoclusters. In principle, the substrate strand immobilized on working electrode acted as the template for the TdT-mediated DNA extension reaction, while the DNAzyme probe would be activated in the absence of miRNA 21, which led to the cleavage of the substrate strand to produce the 5’ phosphate terminus and inhibited the TdT-mediated DNA extension reaction. On the other hand, the presence of miRNA 21 initiated the toehold-mediated strand displacement reaction, causing the disassembly of the DNAzyme structure and preventing the substrate strand from being cleaved. This enabled the recycle amplification of target miRNA 21, and TdT catalyzed the DNA extension reaction on the 3’ hydroxyl terminus of the substrate strand, producing a large number of poly thymine (polyT) sequences. These sequences bound with copper ions for in-situ synthesis of copper nanoclusters on the sensing electrode, and the increased electrochemical signal of copper was recorded by differential pulse stripping voltammetry (DPSV), which paved the way for sensitive determination of miRNA 21 extracted from cancer cells with a detection limit of 36 aM. Due to its high sensitivity, user-friendly operation, and cost-effectiveness, this method is helpful for the fundamental research of sensing mechanism as well as the diagnosis of related diseases.

Toehold and hairpin assembly-mediated tripedal DNA walker for circulating tumor DNA detection in human blood

Circulating tumor DNA (ctDNA) levels in the peripheral blood are correlated with tumor burden and malignant progression. Sensitive and accurate detection of ctDNA in human blood remains to be explored. This study introduces a novel approach that employs toehold-assisted ctDNA capture and hairpin assembly-mediated tripedal DNA walker, facilitating the sensitive detection of a broad range of ctDNAs. Specifically, the design includes a capture probe featuring an overhanging toehold domain for the identification of ctDNA, alongside three hairpin structures that incorporate blocked DNAzymes for the DNA walking mechanism. The capture probe identifies ctDNA through a toehold-mediated strand displacement reaction, which subsequently initiates the assembly of the three hairpin structures, resulting in the formation of a tripedal DNA walker. This tripedal walker is capable of initiating a walking process that generates detectable fluorescent signals for the quantification of ctDNA. The toehold-assisted ctDNA capture method demonstrates excellent accuracy and specificity for identical strands with a single-base mismatch, while the tripedal walker exhibits enhanced efficiency compared to bipedal and unipedal walkers. Furthermore, two stages of signal amplification were achieved, allowing for the sensitive detection of ctDNA with a detection limit of 0.3 fM in buffer solutions and 0.8 fM in serum samples. The quantitative analysis of ctDNA in human blood was effectively performed, demonstrating the method’s ability to distinguish between blood samples from healthy individuals and those from patients with tumor. Therefore, this method represents a significant advancement in ctDNA detection for clinical noninvasive liquid biopsies and holds considerable promise for tumor diagnosis.

Recycling copper wire waste into active Cu-based catalysts for value-added chemicals production via CO2 electrochemical reduction

The CO2 electroreduction reaction (CO2RR) is a method for producing value-added compounds from CO2. This study aimed to use copper from wiring waste to create Cu-based catalysts on Vulcan XC-72R carbon for converting CO2 into valuable chemicals. Copper nanopowder with an average crystallite size of 27 nm derived from the wiring waste solution was utilized as the starting material for mono and bimetallic catalysts preparation. During the bimetallic PdCu/C catalyst synthesis, a galvanic displacement reaction between Pd and Cu occurred, resulting in the formation of PdCu alloy and a reduction in the copper crystallite size. The inclusion of Pd on Cu/C in CO2RR decreased the onset potentials for C1 and C2 chemical production. The yields of methanol, formic acid, and formaldehyde products were generally increased as the Pd:Cu ratio increased. The 1:2-PdCu/C exhibited the smallest crystallite size and an onset potential of less than −1.0 V, resulting in the highest Faradaic efficiency of the products. This catalyst converted CO2 into formic acid (FE = 71.5 %) at a potential of −0.8 V and methanol (FE = 65.4 %) at −0.5 V. The catalyst’s stability was demonstrated for more than 6000 s at current densities of approximately 2 mA /mgcatalyst.