High-Performance Recognition, Cell-Imaging, and Efficient Removal of Carbon Monoxide toward a Palladium-Mediated Fluorescent Sensing Platform

Novel high-performance fluorescent approaches have always significant demand for room-temperature detection of carbon monoxide (CO), which is highly toxic even at low concentration levels and is not easy to recognize due to its colorless and odorless nature. In this paper, we constructed a palladium-mediated fluorescence turn-on sensing platform (TPANN-Pd) for the recognition of CO at room temperature, revealing simultaneously quick response speed (<30 s), excellent selectivity, superior sensitivity, and low detection limit (∼160 nM for CORM-3, ∼1.7 ppb for CO vapor). Moreover, rapid detection and efficient removal (24%) from the air by naked-eye vision has been successfully realized based on TPANN-Pd supramolecular gels. Furthermore, the developed sensing platform was elucidated with low cytotoxicity and high cellular uptake, and it was successfully applied to CO imaging in living cells, providing real-time monitoring of potential CO-involved reactions in biological systems

Sudoku-like Lab-on-Paper Cyto-Device with Dual Enhancement of Electrochemiluminescence Intermediates Strategy

This paper describes the design and construction of a sudoku-like lab-on-paper platform, in which dual enhancement of reaction intermediates strategy was incorporated for multiplexed competitive electrochemiluminescence (ECL) cyto-assay. Benefiting from the sudoku-like structure, integrated multifunctions were obtained on such an elaborately devised platform, including specific reagents storage, multiple samples immobilization, residual automatic washing, and signal collection. By utilizing semicarbazide (SE) and silver nanoparticles (AgNPs) as dual enhancers, more ECL intermediates could be obtained in the graphene quantum dots (GQDs) and peroxydisulfate system, resulting in the production of more excited-state GQDs to emit light. Moreover, the double-stranded DNA nanowire with multiple branched arms (MBdsDNA) was chosen as an efficient nanocarrier to load more GQDs and AgNPs. Via immobilizing AgNPs on the end of the plentiful branched arms, Ag–MBdsDNA were obtained and trapped on the sensing interface through the valid competitive interactions between target cells and Ag–MBdsDNA. Afterward, abundant GQDs were attached to the three-dimensional (3D) DNA skeleton of the captured Ag–MBdsDNA via π–π stacking. Due to their good self-catalytic activity of labeled AgNPs, more silver was deposited on the Ag–MBdsDNA@GQDs, giving rise to further amplification of expected signal. With four types of cancer cells as models, MCF-7, CCRF-CEM, HeLa, and K562 cells were assayed in the ranges of 1.0 × 10²–1.0 × 10⁷, 1.5 × 10²–2.0 × 10⁷, 2.0 × 10²–5.0 × 10⁶, and 1.2 × 10²–2.0 × 10⁶ cells mL^–1 with the detection limits of 38, 53, 67, and 42 cells mL^–1, respectively. Notably, this strategy supplies a simple and versatile platform for sensitive determination of multiple targeted cells, which would play a crucial role in point-of-care diagnostic fields

Turning Nonspecific Interference into Signal Amplification: Covalent Biosensing Nanoassembly Enabled by Metal-Catalyzed Cross-Coupling

In this work, a new method of protein detection in complicated samples is proposed. This method employs probe-target recognition to induce cross-linking among the probe, the target, and the nonspecific proteins in the complicated sample as a means to convert interference into effective signal amplification. This also eliminates the necessity of multistep signal amplification in a separate solution system. On the basis of this strategy, a simple and robust assay for the activity of serum cathepsin B is established. Peptide probes immobilized on a sensing slide can recognize cathepsin B, and this can induce thiol-alkyne covalent coupling between the probe and cathepsin B. Meanwhile, applying electrochemical potential scanning to this sensing surface, Cu binding fragments of the probe peptide can be released into the solution phase to act as an electrochemical catalyst for oxidative dityrosine cross-linking among all proteins including the captured cathepsin B and the nonspecific proteins. A continuous nanoassembly covalently anchored on the sensing surface can gradually form, allowing violent detergent rinsing to remove residual interference. Using this method, not only sensitivity in the picomolar range can be achieved for serum analysis, the results of the analysis can also reliably discriminate benign and cancerous ovarian conditions. These results may suggest prospective application of this method in early screening of cancer in the future

Metal-Enhanced Ratiometric Fluorescence/Naked Eye Bimodal Biosensor for Lead Ions Analysis with Bifunctional Nanocomposite Probes

A novel metal-enhanced ratiometric fluorescence/naked eye bimodal biosensor based on ZnFe₂O₄@Au–Ag bifunctional nanocomposite and DNA/CeO₂ complex for lead ions (Pb²⁺) has been successfully developed. The nanocomposite probe was composed of a magnetic ZnFe₂O₄ core and a Au–Ag hollow nanocube shell. Upon bioconjugation, bifunctional magnetic nanocomposites could not only make the probe possess excellent recyclability but also provide an enrichment of “hot spots” for surface enhanced fluorescence detection of Pb²⁺ by a metal-enhanced fluorescence effect. Typically, the bifunctional nanocomposites conjugated with double-stranded DNA (included Pb²⁺-specific DNAzyme strand and corresponding substrate strand) to form a Pb²⁺ biosensor. Nanoceria as a fluorescence quencher strongly adsorbed DNA. Therefore, the formation of double-stranded DNA brought the labeled nitrogen sulfur doped carbon dots (N,S-CDs) and CeO₂ into close proximity, which significantly quenched the fluorescence of N,S-CDs. The presence of Pb²⁺ led to the breakage of the DNAzyme strand, resulting in the fluorescence signal of Cy3 decreasing, while the fluorescence intensity of N,S-CDs aggrandized. First, a preliminary test of Pb²⁺ was performed by the naked eye. The disengaged DNA/CeO₂ complex could result in color change after adding H₂O₂ because of autocatalysis of CeO₂, resulting in real-time visual detection of Pb²⁺. If further accurate determination was required, the fluorescence intensity ratio of these two fluorescence indicators was measured at 562 and 424 nm (<i>I</i>₅₆₂/<i>I</i>₄₂₄). A good linear correlation exists between the log­(<i>I</i>₅₆₂/<i>I</i>₄₂₄) and the logarithm of Pb²⁺ concentrations ranging from 10^–12 to 3 × 10^–6 M. Remarkably, the detection limit of this ratiometric biosensor was 3 × 10^–13 M, which ascribed to its superior fluorescence enhancement. Interestingly, the developed bifunctional nanocomposite probe manifests good recyclability and selectivity. More importantly, the biosensor provided potential application of on-site and real-time unknown Pb²⁺ ions in real systems

Three-Decker Strategy Based on Multifunctional Layered Double Hydroxide to Realize High-Performance Hydroxide Exchange Membranes for Fuel Cell Applications

Herein, we present a three-decker layered double hydroxide (LDH)/poly­(phenylene oxide) (PPO) for hydroxide exchange membrane (HEM) applications. Hexagonal LDH is functionalized with highly stable 3-hydroxy-6-azaspiro [5.5] undecane (OH-ASU) cations to promote it’s ion-exchange capacity. The ASU-LDH is combined with triple-cations functionalized PPO (TC-PPO) to fabricate a three-decker ASU-LDH/TC-PPO hybrid membrane by an electrostatic-spraying method. Notably, the ASU-LDH layer with a porous structure shows many valuable properties for the ASU-LDH/TC-PPO hybrid membranes, such as improving hydroxide conductivity, dimensional stability, and alkaline stability. The maximum OH^– conductivity of ASU-LDH/TC-PPO hybrid membranes achieves 0.113 S/cm at 80 °C. Only 11.5% drops in OH^– conductivity was detected after an alkaline stability test in 1 M NaOH at 80 °C for 588 h, prolonging the lifetime of the TC-PPO membrane. Furthermore, the ASU-LDH/TC-PPO hybrid membrane realizes a maximum power density of 0.209 W/cm² under a current density of 0.391 A/cm². In summary, the ASU-LDH/TC-PPO hybrid membranes provide a reliable method for preparing high-performance HEMs

Photoelectrochemical Lab-on-Paper Device Based on an Integrated Paper Supercapacitor and Internal Light Source

In this work, a photoelectrochemical (PEC) method was introduced into a microfluidic paper-based analytical device (μ-PAD), and thus, a truly low-cost, simple, portable, and disposable microfluidic PEC origami device (μ-PECOD) with an internal chemiluminescence light source and external digital multimeter (DMM) was demonstrated. The PEC responses of this μ-PECOD were investigated, and the enhancements of photocurrents in μ-PECOD were observed under both external and internal light sources compared with that on a traditional flat electrode counterpart. As a further amplification of the generated photocurrents, an all-solid-state paper supercapacitor was constructed and integrated into the μ-PECOD to collect and store the generated photocurrents. The stored electrical energy could be released instantaneously through the DMM to obtain an amplified (∼13-fold) and DMM-detectable current as well as a higher sensitivity than the direct photocurrent measurement, allowing the expensive and sophisticated electrochemical workstation or lock-in amplifier to be abandoned. As a model, sandwich adenosine triphosphate (ATP)-binding aptamers were taken as molecular reorganization elements on this μ-PECOD for the sensitive determination of ATP in human serum samples in the linear range from 1.0 pM to 1.0 nM with a detection limit of 0.2 pM. The specificity, reproducibility, and stability of this μ-PECOD were also investigated

Cerium Dioxide-Mediated Signal “On–Off” by Resonance Energy Transfer on a Lab-On-Paper Device for Ultrasensitive Detection of Lead Ions

In this report, a 3D microfluidic lab-on-paper device for ultrasensitive detection of lead cation was designed using phoenix tree fruit-shaped CeO₂ nanoparticles (PFCeO₂ NPs) as the catalyst and 50 nm silver NPs (Ag NPs) as the quencher. First, snowflake-like Ag NPs were grown on the paper working electrode through an in situ growth method and used as a matrix for DNAzymes that were specific for lead ions (Pb²⁺). After the addition of Ag NP-labeled substrate strands, the Ag NPs restrained the electrochemiluminescence (ECL) intensity of luminol greatly through the resonance energy transfer from luminol to Ag NPs. However, under the existence of Pb²⁺, the substrate strands were separated, and then PFCeO₂ NP-labeled signal strands were hybridized with the DNAzymes. The ECL signal was improved greatly under the fast catalytic reaction between PFCeO₂ NPs and H₂O₂, which converted the response from signal off to signal on state, resulting in sensitive detection of Pb²⁺. Under the optimal conditions, the ECL signal response exhibited a good linear relationship with the logarithm of lead cation in a wide linear range of 0.05–2000 nM and an ultralow detection limit of 0.016 nM. Meanwhile, a sensor featured with good specificity, acceptable stability, reproducibility, and low cost provides a promising portable, simple, and effective strategy for Pb²⁺ detection

Paper-Based Analytical Devices Relying on Visible-Light-Enhanced Glucose/Air Biofuel Cells

A strategy that combines visible-light-enhanced biofuel cells (BFCs) and electrochemical immunosensor into paper-based analytical devices was proposed for sensitive detection of the carbohydrate antigen 15-3 (CA15-3). The gold nanoparticle modified paper electrode with large surface area and good conductibility was applied as an effective matrix for primary antibodies. The glucose dehydrogenase (GDH) modified gold–silver bimetallic nanoparticles were used as bioanodic biocatalyst and signal magnification label. Poly­(terthiophene) (pTTh), a photoresponsive conducting polymer, served as catalyst in cathode for the reduction of oxygen upon illumination by visible light. In the bioanode, electrons were generated through the oxidation of glucose catalyzed by GDH. The amount of electrons is determined by the amount of GDH, which finally depended on the amount of CA15-3. In the cathode, electrons from the bioanode could combine with the generated holes in the HOMO energy level of cathode catalysts pTTh. Meanwhile, the high energy level photoexcited electrons were generated in the LUMO energy level and involved in the oxygen reduction reaction, finally resulting in an increasing current and a decreasing overpotential. According to the current signal, simple and efficient detection of CA15-3 was achieved

Stackable Lab-on-Paper Device with All-in-One Au Electrode for High-Efficiency Photoelectrochemical Cyto-Sensing

Highly conductive, robust, and multifunctional integrated paper-supported electrodes are requisite to fulfill the promise of paper-based analytical application. Herein, an all-in-one Au electrode comprising of detection zone, waterproof electronic bridge, and signal output contactor was engineered via combining the double-sided growth method with the secondary wax-printing. Benefiting from the strongly omnidirectional conductivity and desirably mechanical robustness of the as-prepared electrode, a stackable lab-on-paper cyto-device integrated with high-efficiency photoelectrochemical strategy was developed for the MCF-7 cells assay. Specifically, the detection zone of the electrode, serving as the signal generator, was functionalized with a low-toxic cosensitized structure composed of corn-like ZnO nanorods, graphene quantum dots (GQDs), and Ag₂Se QDs. With the proximity control of DNA hairpin-based aptamer probe (DHAP), a strong photocurrent could be promoted by the activated cosensitization effect and collected on the signal output contactor via the electron transport of waterproof electronic bridge. Upon the MCF-7 cells recognition, the DHAP switched from closed to open state with the formation of DNA-cell bioconjugates and the spatial separation of Ag₂Se QDs linked on the terminal of DHAP from the electrode surface. The photocurrent was noticeably decreased due to the double inhibition of steric hindrance effect and vanished cosensitization effect. Based on the target-triggered photocurrent attenuation, the sensitive detection of target cells was achieved. This work not only provided a unique method for paper-based electrode preparation but also offered a powerful platform for the highly sensitive photoelectrochemical bioanalysis

Characteristics of female subjects grouped by ACE and A3B genotypes.

a<p>belong to categorical variables.</p>b<p>Analysis of covariance can not be employed because the data can't be transformed to normality.</p><p>Abbreviations: BMI, body mass index; HDL, high density lipoprotein; LDL, low density lipoprotein; BUN, blood urea nitrogen; ALT, alanine aminotransferase; γ–GT, gamma-glutamyl transpeptidase; AST, aspartate aminotransferase.</p