Dual Recycling Research Articles

Chain-End Controlled Depolymerization Selectivity in α,α-Disubstituted Propionate PHAs with Dual Closed-Loop Recycling and Record-High Melting Temperature.

Within the large poly(3-hydroxyalkanoate) (PHA) family, C3 propionates are much less studied than C4 butyrates, with the exception of α,α-disubstituted propionate PHAs, particularly poly(3-hydroxy-2,2-dimethylpropionate), P3H(Me)2P, due to its high melting temperature (Tm ∼ 230 °C) and crystallinity (∼76%). However, inefficient synthetic routes to its monomer 2,2-dimethylpropiolactone [(Me)2PL] and extreme brittleness of P3H(Me)2P largely hinder its broad applications. Here, we introduce simple, efficient step-growth polycondensation (SGP) of a hydroxyacid or methyl ester to afford P3H(Me)2P with low to medium molar mass, which is then utilized to produce lactones through base-catalyzed depolymerization. The ring-opening polymerization (ROP) of the 4-membered lactone leads to high-molar-mass P3H(Me)2P, which can be depolymerized by hydrolysis to the hydroxyacid in 99% yield or methanolysis to the hydroxyester in 91% yield, achieving closed-loop recycling via both SGP and ROP routes. Intriguingly, the chain end of the SGP-P3H(Me)2P determines the depolymerization selectivity toward 4- or 12-membered lactone formation, while both can be repolymerized back to P3H(Me)2P. Through the formation of copolymers P3H(Me/R)2P (R = Et, nPr), PHAs with high tensile strength and ductility, coupled with high barriers to water vapor and oxygen, have been created. Notably, the PHA structure-property study led to P3H(nPr)2P with a record-high Tm of 266 °C within the PHA family.

Approaches of frequency-dependent squeezing for the low frequency detector of the Einstein Telescope

The quantum noise in gravitational-wave detectors can be suppressed in a broadband by frequency-dependent squeezing. It usually requires one large scale filter cavity and even two, for example in the low frequency detector of Einstein Telescope, which is a detuned dual recycling Fabry-Perot Michelson interferometer. In this paper, we study the feasibility of replacing two filter cavities with a coupled-cavity, aiming to reduce the optical losses with less number of optics. It turns out this approach is only theoretically valid, however, the required parameters of the optics do not support practical implementation, which is consistent with the results in Jones [Implications of the quantum noise target for the Einstein Telescope infrastructure design, ]. Furthermore, we investigate the viability of utilizing Einstein-Podolsky-Rosen (EPR) squeezing to eliminate either one or two filter cavities in the Einstein Telescope. It turns out EPR squeezing would allow us to eliminate one filter cavity, and can potentially improve the detector sensitivity with the allowance of higher input squeezing level, benefiting from the longer length of the arm cavity which serves as one of the filter cavities for frequency-dependent squeezing. Published by the American Physical Society 2024

Reverse supply chain decisions with online and offline dual recycling channels considering consumer fairness concerns and channel preference

Online recycling is becoming more prevalent as a result of the quick development of innovative technologies to enhance the recycling system. Based on consumer fairness concerns and channel preferences, we establish an online and offline dual-recycling channel reverse supply chain model in which a processor dominates and a recycler follows according to Stackelberg game theory and investigates the impact of two consumer’s behavioral preferences upon supply chain decisions. The results show that: (1) for the game leader, the impact of consumer fairness concerns is greater than that of channel preference; (2) for the game follower, the impact of channel preference is greater than that of consumer fairness concerns; (3) entrusting the recycler to collect can help the leader reduce profit losses caused by consumer fairness concerns.

A Dual-Channel Cooperative Strategy between Recyclers and E-Tailers for the Offline and Online Recycling of Waste Electronics

A Stackelberg game model was formulated for dual recycling channels for a supply chain with a recycler and an e-tailer, who recycle and resell waste electronics. A reverse solution was adopted to find the optimal recycling prices, the optimal selling prices, and the supply chain’s overall profits for cooperative and non-cooperative models. The profits gained in the cooperative model were greater. We proposed a revenue-sharing contract to investigate the profit distribution. Finally, we validated the effectiveness of the cooperative recycling model through numerical simulations, calculated the revenue-sharing factors, and analyzed the effects of these factors on the decisions of the recycler and the e-tailer. By comparing the dual-channel non-cooperative recycling model based on online and offline recycling by the recycler to the dual-channel cooperative recycling model based on offline recycling by the recycler and online recycling by the e-tailer, as well as examining the results in relation to the contracts, we found that the recycler and the e-tailer should cooperate in recycling electronics to maximize the supply chain’s overall profits. However, the e-tailer will see reduced profits and may be less willing to cooperate, so it is necessary to formulate a revenue-sharing contract. The revenue-sharing factors in the contract must be set within a reasonable range; otherwise, either party could see reduced profits and renounce cooperation, even if the supply chain’s overall profit is maximized. The recycler is the more critical party for achieving cooperation. In this paper, we research the cooperative strategy between recyclers and e-tailers that is conducive for expanding the market scale of waste electronics recycling and improving the profits of both parties, while promoting the sustainable development of the supply chain.

Promoting consumer returns in closed-loop supply chains under cap-and-trade regulation: A cooperative recycling advertising perspective

Under carbon cap-and-trade regulation, to control carbon emissions and improve the recycling efficiency of waste electrical and electronic equipment (WEEE) from the traditional offline recycling channel, more enterprises attempt to simultaneously combine the online recycling platform with the digital transformation of the supply chain. Based on a closed-loop supply chain (CLSC) with dual recycling channels and considering recycling advertising invested both in offline and online recycling channels, this paper attempts to explore the optimal recycling advertising mode which can both achieve economic and environmental performance under cap-and-trade regulation. Therefore, game models including a manufacturer and above either recycler are established, which are respectively correspond to four recycling advertising modes: manufacturer cooperates with neither recycler (MO mode), manufacturer only cooperates with the offline retailer (MR mode), manufacturer only cooperates with the online recycling platform (MT mode), and manufacturer cooperates with either recycler (MRT mode). Consequently, this paper solves the optimal decisions of the tripartite and focuses on the analysis of the impact of cooperative (competitive) recycling advertising under cap-and-trade regulation. By comparing the profits and total carbon emissions of the whole CLSC under four recycling advertising modes, the results indicate that: cooperative advertising between the manufacturer and two recyclers can achieve economic and environmental performance for the whole CLSC if the free-riding phenomenon occurs in recycling advertising. Otherwise, influenced by competitive recycling advertising, the above mode turns to the suboptimal one for the profits of two recyclers and the total carbon emissions of the CLSC. Moreover, driven by economic benefits, cooperative advertising will eventually become a consensus, but the total carbon emissions may not always be the least.

A Recent Digitalization in Recycling Industry Attaining Ecological Sustainability: A Comprehensive Outlook and Future Trend.

The management of waste through dual way of recycling (i-e offline and online) is assumed to have a key role in attaining ecological sustainability and enabling circular practices. The research on online recycling is gaining evolution in recent age. Prior literature on the current research theme has failed to provide a comprehensive outlook and future trend. Therefore, the current research intends to elaborate the current research scenario linked with online recycling by critically scrutinizing the prior research over the last 41 years. A comprehensive analysis was conducted using the Scopus database, retrieving a total of 866 articles. These articles were selected to provide a conceptual overview and understanding of the fundamental research conducted in the field. By employing bibliometric analysis this research provides comprehensive detail about evolution, mapping of publications and prominent trends from the year 1981 to 2022 to understand the practices and future trends of online recycling research. The outcomes elucidated that there is exponential increase in research publications relating to online recycling over the last five years. The most influential producer of online recycling research are China, United Kingdom and United States. Chinese Universities has the highest number of publications among all the countries across globe. Moreover, the current research trend is focused on technology based circular economy, industrial ecology, bio-based waste management, dual channel recycling, municipal waste, waste from electrical and electronic equipment (WEEE), environmental impact and lifecycle assessment. Hence, the prominent research perspective and highlighted features could offer recommendation for upcoming studies to contribute in literature and help practitioners, policymakers and professionals move towards circular practices.

Target Recognition Initiated Self-Assembly-Based Signal Amplification Strategy for Sensitive and Colorimetric Staphylococcus aureus Detection and Diagnosis of Skin Infection.

Staphylococcus aureus (S. aureus), as a Gram-positive bacterium, is commonly encountered in various infectious diseases, such as acute skin and soft tissue infections. Despite that many efforts have been made, sensitive and reliable quantitative determination of S. aureus remains a huge challenge. Here, we depict a novel colorimetric approach for sensitive and accurate detection by combining allosteric probe-based target recognition and chain extension-based dual signal recycling. The single-strand DNA (ssDNA) products generated by the chain extension process lead to the liberation of G-quadruplex sequences, which can fold into active DNAzyme under the assistance of hemin. The active DNAzyme can work as peroxidase mimics to catalyze the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS2-)-H2O2 system, causing the color change of the system. Eventually, the method exhibits a wide detection range from 103cfu/mL to 106cfu/mL. The limit of detection of the approach was determined 232cfu/mL. Considering the robust capability of the approach in S. aureus detection, we believe that it will be a potential alternative tool for biomedical research and clinical molecular diagnostics.

Dual DNA recycling amplifications coupled with Au NPs@ZIF-MOF accelerator for enhanced electrochemical ratiometric sensing of pathogenic bacteria

Sensitive and accurate quantification of pathogenic bacteria is vastly significant to the related food safety. Herein, a sensitive ratiometric electrochemical biosensor was developed for the detection of Staphylococcus aureus (S. aureus) based on dual DNA recycling amplifications and Au NPs@ZIF-MOF accelerator. Gold nanoparticles-loaded Zeolitic imidazolate metal-organic framework (Au NPs@ZIF-MOF) as electrode substrate possessed a large specific surface area for nucleic acid adsorption, and as an accelerator promoted the transfer of electrons. The strong recognition of aptamer to target S. aureus could initiate the padlock probe-based exponential rolling circle amplification (P-ERCA, as the first DNA recycling amplification), generating large numbers of trigger DNA strands. The released trigger DNA further activated the catalytic hairpin assembly (CHA, as the second DNA recycling amplification) on electrode surface. Consequently, P-ERCA and CHA continuously brought about one target to many signal transduction, leading to an exponential amplification. To achieve the accuracy of detection, the signal ratio of methylene blue (MB) and ferrocene (Fc) (IMB/IFc) was applied for intrinsic self-calibrating. Taking advantages of dual DNA recycling amplifications and Au NPs@ZIF-MOF, the proposed sensing system displayed high sensitivity for S. aureus quantification with a linear range of 5–108 CFU/mL, and the limit of detection was 1 CFU/mL. Moreover, this system represented excellent reproducibility, selectivity, and practicability for S. aureus analysis in foods.

Dual Recycling of Depolymerization Catalyst and Biodegradable Polyester that Markedly Outperforms Polyolefins.

Chemically recyclable, circular polymers continue to attract increasing attention, but rendering both catalysts for depolymerization and high-performance polymers recyclable is a more sustainable yet challenging goal. Here we introduce a dual catalyst/polymer recycling system in that recyclable inorganic phosphomolybdic acid catalyzes selective depolymerization of high-ceiling-temperature biodegradable poly(δ-valerolactone) in bulk phase, which, upon reaching suitable molecular weight, exhibits outstanding mechanical performance with a high tensile strength of ≈66.6 MPa, fracture strain of ≈904 %, and toughness of ≈308 MJ m-3 , and thus markedly outperforms commodity polyolefins, recovering its monomer in pure state and quantitative yield at only 100 °C. In sharp contrast, the uncatalyzed depolymerization not only requires a high temperature of >310 °C but is also low yielding and non-selective. Importantly, the recovered monomer can be repolymerized as is to reproduce the same polymer, thereby closing the circular loop, and the recycled catalyst can be reused repeatedly for depolymerization runs without loss of its catalytic activity and efficiency.

Dual Recycling of Depolymerization Catalyst and Biodegradable Polyester that Markedly Outperforms Polyolefins

AbstractChemically recyclable, circular polymers continue to attract increasing attention, but rendering both catalysts for depolymerization and high‐performance polymers recyclable is a more sustainable yet challenging goal. Here we introduce a dual catalyst/polymer recycling system in that recyclable inorganic phosphomolybdic acid catalyzes selective depolymerization of high‐ceiling‐temperature biodegradable poly(δ‐valerolactone) in bulk phase, which, upon reaching suitable molecular weight, exhibits outstanding mechanical performance with a high tensile strength of ≈66.6 MPa, fracture strain of ≈904 %, and toughness of ≈308 MJ m−3, and thus markedly outperforms commodity polyolefins, recovering its monomer in pure state and quantitative yield at only 100 °C. In sharp contrast, the uncatalyzed depolymerization not only requires a high temperature of >310 °C but is also low yielding and non‐selective. Importantly, the recovered monomer can be repolymerized as is to reproduce the same polymer, thereby closing the circular loop, and the recycled catalyst can be reused repeatedly for depolymerization runs without loss of its catalytic activity and efficiency.

A graphene-oxide-based fluorometric assay for norA gene transcription in MRSA using Nb.BbvCI-assisted target recycling and T7 exonuclease-triggered cascade dual recycling signal amplification

We describe a graphene oxide (GO)-based bioassay for the fluorometric determination of norA gene transcription (mRNA) in methicillin-resistant Staphylococcus aureus (MRSA). This approach is based on Nb.BbvCI-assisted target recycling (NATR) and T7 exonuclease (T7 Exo)-triggered cascade dual-recycling signal amplification (TTCDRSA). The system included GO, a capture probe (CP), an assistant probe (AP), two carboxyfluorescein (FAM)-labeled hairpins (HP1 and HP2), endonuclease Nb.BbvcI, and exonuclease T7. In the presence of a target, AP, together with the target RNA, can hybridise with CP via partial complementarity to one another and open its hairpin structure to form a triple complex that is recognised by Nb.BbvCI. Once the CP is cleaved, the released AP and target RNA can walk on the carboxylated graphene oxide (CGO) surface to bind with another CP which induces the next round of cleavage, accumulating many trigger probes (TPs). The TPs then activate TTCDRSA with the assistance of T7 Exo, HP1, and HP2 to produce large amounts of free FAMs. These free FAMs are repelled by GO and exhibit enhanced fluorescence signals at excitation/emission wavelengths of 480/514 nm. The limit of detection (LOD) of the bioassay was calculated to be 0.37 fM, and the linear range of the method ranged from 1 fM to 1 nM. More importantly, the bioassay also exhibited high sensitivity and selectivity for target RNA detection in real samples, which may open a new promising avenue for monitoring drug efflux and studying the mechanisms of drug actions.

Dual cascade nucleic acid recycling-amplified assembly of hyperbranched DNA nanostructures to construct a novel plasmonic colorimetric biosensing method.

The plasmonic colorimetric biosensors are very favorable for the on-site testing and naked-eye screening of analytes from real samples, but how to realize their highly sensitive assays with simple manipulations is still a great challenge. Herein we designed a target-triggered dual cascade nucleic acid recycling strategy to amplify the assembly of a hyperbranched DNA nanostructure and thus developed a novel kanamycin colorimetric biosensing method. The first cycle arising from the aptamer recognition-triggered strand displacement reaction and its cascade cycle constructed on the catalytic reaction of two nucleases could release an output DNA to trigger the assembly of the DNA nanostructure. Based on the high capture of alkaline phosphatase at this DNA nanostructure to induce the localized surface plasmon resonance change of gold nanobipyramids (Au NBPs), an ultrasensitive colorimetric signal transduction strategy was constructed. Through the measurement of the shift of the characteristic absorption wavelength of Au NBPs, a very wide linear range from 10 fg mL-1 to 1 ng mL-1 and a very low detection limit of 1.4 fg mL-1 were obtained. Meanwhile, the obvious multicolor change of Au NBPs could be used for the visual semi-quantitative analysis of Kana residues. The whole homogeneous assay process well simplified the manipulation and also ensured the excellent repeatability. These excellent performances determine the great potential of the method for future applications.

High efficient electrochemical biosensor based on exonuclease-Ⅲ-assisted dual-recycling amplification for ultrasensitive detection of kanamycin

A target-triggered and exonuclease-Ⅲ-assisted strand displacement, dual-recycling amplification reaction-based biosensor was developed for the rapid, ultrasensitive and accurate detection of kanamycin. The robust profiling platform was constructed using high conductive MXene/VS2 for the electrode surface modification and high active CeCu2O4 bimetallic nanoparticles as nanozyme to improve the sensitivity as well as the catalytic signal amplification of the biosensor. Using the dual supplementary recycling of primer DNA and hairpin DNA, the electrochemical platform could accurately detect kanamycin to as low as 0.6 pM from the range of 5 pM to 5 μM. By profiling five other antibiotics, this platform exhibited high specificity, enhanced repeatability and reproducibility. Based on these intrinsic characteristics and by utilizing milk and water samples, the as-designed biosensor offers a remarkable strategy for antibiotic detection due to its favorable analytical accuracy and reliability, thereby demonstrating potential application prospect for various antibiotic biosensing in food quality control, water contamination detection and biological safety analysis.

Mechano-chemical rubber reclamation using aminolysis products of waste flexible polyurethane foams as the devulcanizing agent

Rubber and polyurethane are polymers that are widely used but difficult to decompose in the natural environment. In this work, polyurethane aminolysis products (PAPs) are used to assist in the devulcanization of waste rubbers for the first time. The amine groups contained in PAPs can couple with the radicals generated by the scissions of crosslink bonds under the action of mechanical shear force, enhance the degree of devulcanization, and thus improve the mechanical properties of the reclaimed rubbers (RRs). The addition of PAPs can also shorten the optimum cure time of the RRs and improve the crosslink density and hardness of the RR re-vulcanizates. Using 1.8 phr of lower-layer PAPs prepared at 120 °C, the RR re-vulcanizate exhibit a tensile strength of 16.48 MPa, an elongation at break of 330.2%, and a tear strength of 48.5 MPa. This method realizes the dual high-value recycling of waste polyurethanes and rubbers, exhibiting bright application prospects.

Effects of alkali-treated plant wastewater on the properties and microstructures of alkali-activated composites

Naturally available plants such as fiber, straw, sawdust, and wood used as reinforcing additives in building materials require an alkali treatment to reduce the moisture sensitivity of additives and to interlock matrix and additive. However, the discharge of alkali-treated plant wastewater (ATPW) is extremely detrimental to the environment. The purpose of this study is to evaluate the effects of recycled ATPW from NaOH-treated sisal leaves, poplar leaves, poplar stems, and corn stems on the characteristics and microstructures of alkali-activated composite materials (AACMs) made from solid wastes. The ATPWs were produced by soaking green and dead plants for 24 h in a 15% NaOH solution. The AACMs were manufactured using ATPW as an alkaline activator and a mixture of slag powder, red mud, fly ash, and steel slag as a binder. The fresh and hardened properties, such as electrical conductivity (EC), fluidity, flexural strength, compressive strength, and density, were examined along with drying shrinkage resistance. Furthermore, SEM, EDS, CT, and FTIR techniques were used to observe and evaluate the pore distributions, morphologies, and products. The results demonstrate that the effects of ATPWs produced from dead sisal leaves were remarkable on the properties and microstructures of AACMs. The sample (DSL) with ATPW exhibits an increase of 43.08% in fluidity and a drop of 50.00% in EC, 44.30% in density, 34.25% in dry shrinkage, 84.44% in flexural strength, and 88.50% in compressive strength, relative to the control without ATPW. Moreover, AACMs physically sequester the organic components of ATPW during the early stage of hardening. The ATPW serves as a unique physical foaming agent in AACMs. The results provide original data on the dual recycling of industrial wastewater and solid waste to promote clean operations.

To Share or Not to Share? The Role of Retailer's Information Sharing in a Closed-Loop Supply Chain.

Retailers are faced with a dilemma of whether to share demand information with other supply chain members, and if so, how to share it. Our research interest is motivated by the grounds that the value of downstream retailers’ sales information to upstream manufacturers is to improve the accuracy of manufacturers’ order forecasting. This problem is particularly important in the remanufacturing of closed-loop supply chains (CLSCs). In this study, we consider a retailer (she) as the demand information holder, who sells new and remanufactured products in wholesale to a manufacturer (he) and, simultaneously, she and the manufacturer competitively collect used products from the customers. We explicitly characterize the role of information sharing in a CLSC. We contributed to the information-sharing literature by integrating the existing information-sharing model with dual recycling channels and channel power structure. Previous literature suggests that retailers prefer to share demand information with other firms when the market demand is high. However, surprisingly, we find that when the manufacturer does not play a leading role, the retailer shares her forecast demand information with the manufacturer if the market demand is low. We also show that information sharing reduces the overall profit of the supply chain when the manufacturer dominates the market. In addition, our results also illustrate that information sharing affects the performance of the supply chain mainly by affecting the wholesale price.

CAD Design for Recycling and Utilization of Waste Packaging from the Perspective of Ecological Criticism

In order to realize the value of packaging waste through recycling, detection, classification, maintenance, and reprocessing, the model construction and simulation study of logistics packaging recycling and utilization were put forward. This paper takes logistics companies as the research object, aiming at the business model of logistics companies, uses the Internet of things recycling machine for packaging recycling, and establishes a dual channel packaging recycling model. This model is intended to compare and analyze the difference between traditional packaging waste recycling channel and intelligent recycling machine of the internet of things in terms of recycling cost, profit, recovery rate, waste incineration rate, and other aspects. It is assumed that the recycling proportion of the two channels accounts for half of the packaging waste. The results of simulation analysis on recycling and utilization of dual-channel packaging waste show that in the simulated time period, the recycling rate of the intelligent recycling machine using the internet of things is higher than that of the traditional dispersed recycling vendors. Assume that when the recycling frequency = 2, when the recycling frequency is increased to 2 times a day, the recycling time of the internet of things recycling machine is further shortened, and the recycling efficiency is improved. At the same time, due to the improvement of the recycling rate of the internet of things recycling machine, the amount of waste packaging decreases, so the recycling rate of the dispersed recycling vendors decreases accordingly. The recycling revenue and net profit generated by channel 2 (internet of things recycling machine) are higher than those generated by channel 1 (decentralized recycling vendor responsible for recycling). The average profit of channel 2 is about 28,163.69 yuan, while the average profit of channel 1 is only 9,395.89 yuan. The waste recovered through channel 2 is lower than that in channel 1; the average for channel 1 is 15.58 tons. However, the average value of channel 2 is 14.58 tons. Comprehensive analysis shows that channel 2 has obvious advantages in reducing waste discharge. However, it is necessary to strengthen the research and development of recycling technology, improve the reuse efficiency, and reduce the incineration of nonreusable waste as much as possible to the minimum, which proves the robustness of this paper to the logistics packaging recycling model construction. It is proved that the robustness of this paper for logistics packaging recycling model construction provides strong support for the analysis of waste pallets and packaging recycling-related issues.

Ultrasensitive detection of patulin based on a Ag+-driven one-step dual signal amplification

Due to improper storage, the presence of patulin in fruits poses a threat to food safety. Herein, a one-step dual amplification strategy-based electrochemical aptasensor was proposed for patulin detection. Silver-palladium nanoparticles (AgPdNPs) with a hollow and branched structure were used as a supporting material for thionine to provide numerous attachment sites. AuNFs/g-C3N4 was employed as an electrode modification material, which has been demonstrated to facilitate electron transport and improve signal label loading capacity. Ag+ ions were released in the presence of patulin, activating the Ag+-DNAzyme on the electrode surface. The formed Ag+-DNAzymes further cyclically cleaved the substrate DNA, and the released sequences were used as a new trigger to mediate the secondary recirculation. This one-step dual amplification strategy enabled double target recycling without additional procedures. The signal cascade amplification through dual target recycling, was thus available for trace detection of patulin. Under the optimal conditions, the electrochemical aptasensor achieved a satisfactory linear range from 5.0 × 10-6 μg L-1 to 50 μg L-1 with a detection limit of 0.92 fg·mL-1 for the determination of patulin. In addition, the aptasensor exhibited favorable selectivity, reproducibility, repeatability and long-term stability, and thus can be employed for patulin detection in apple juice samples, providing excellent choice for the detection of trace patulin.

Trimetallic nanoparticle-decorated MXene nanosheets for catalytic electrochemical detection of carcinoembryonic antigen via Exo III-aided dual recycling amplifications

Changes in trace levels of tumor markers are important indicators for diagnosing and treating different diseases, including cancers. On account of a recycled dual amplification approach aided by exonuclease III (Exo III) and the trimetallic nanoparticle-decorated MXene nanosheet (Au-Pd-Pt/Ti3C2Tx)-modified electrode as the catalytic sensing interface, we describe the establishment of a label-free and aptamer-based sensitive carcinoembryonic antigen (CEA) detection assay platform. The target CEA molecules bind the aptamer containing hairpin probes to trigger cyclic cleavage of the secondary hairpins with the assistance of Exo III to release a large amount of ssDNAs, which further hybridize with the G-quadruplex-integrated triple-helix complex (THC) signal probes on the sensor electrode. Exo III then cyclically cleaves the resulting duplexes to liberate many G-quadruplex sequences that can confine hemin on the electrode surface. Subsequent catalytic reduction of H2O2 mediated by hemin on Au-Pd-Pt/Ti3C2Tx-modified sensing interface thus yields drastically enhanced current signals for detecting CEA with high sensitivity between 1 fg mL−1 and 1 ng mL−1 with the detection limit of 0.32 fg mL−1. Such a demonstration of our assay method for CEA indicates that the developed sensing platform can be extended as a promising means for sensitive monitoring of different molecular biomarkers.

A universal constructing method for high performance DNA biosensors based on the optimized photoelectrode material and dual recycling amplification

Many effective strategies for photoelectrochemical DNA sensors have been developed in the past decades. Most of them focused on the detection performance including sensitivity, limit of detection and linear range, but few on the pivotal roles of photoelectrode materials and the universality for strategies. Herein, the photoelectrode material was optimized by density functional theory for improving the comprehensive performances of DNA biosensor for the first time. And the universal strategies, based on dual recycling amplification, was discussed by different nucleic acid sequences. After systematical optimization of detection conditions, a large linear range of 10-16 to 10-6 M, high sensitivity of 5.66 μA·cm−2·dec-1 and low limit of detection of 10-18 M (a gene copy per microliter) were achieved for the detection of DNA sequences from the I27L gene. Finally, detection of DNA sequences from Orientia tsutsugamushi was used to prove the universality of the novel method.