Catalytic Hairpin Assembly-Driven Ratiometric Dual-Signal Electrochemical Biosensor for Ultrasensitive Detection of MicroRNA Based on the Ratios of Fe-MOFs and MB-GA-UiO-66-NH2.

In this work, a novel ratio electrochemical biosensing platform based on catalytic hairpin assembly target recovery to trigger dual-signal output was developed for ultrasensitive detection of microRNA (miRNA). To achieve the ratiometric dual-signal strategy, methylene blue (MB), an electrochemical indicator, was ingeniously loaded into the pores of graphene aerogel (GA) and metal-organic framework (MOF) composites with high porosity and large specific surface area, and another electrochemical indicator Fe-MOFs with distinct separation of redox potential was selected as a signal probe. Concretely, with the presence of the target miRNA, the CHA process was initiated and the signal probe was introduced to the electrode surface, producing abundant double-stranded H1-H2@Fe-MOFs-NH2. Then, the measurement and analysis of the prepared ratiometric electrochemical biosensor by differential pulse voltammetry (DPV) showed that the introduction of the target miRNA led to an increase in the oxidation peak signal of Fe-MOFs (+0.8 V) and a decrease in the oxidation peak signal of MB (-0.23 V). Therefore, the peak current ratio of IFe-MOFs/IMB could be employed to accurately reflect the actual concentration of miRNA. Under optimal conditions, the detection limit of the proposed biosensor was down to 50 aM. It was worth noting that the proposed biosensor exhibited excellent detection performance in a complex serum environment and tumor cell lysates, showing great potential in biosensing and clinical diagnosis.

A disposable and sensitive non-enzymatic glucose sensor based on a 3D-Mn-doped NiO nanoflower-modified flexible electrode.

Herein, nanoflower-shaped Mn-doped NiO nano-enzyme composites with high catalytic performance and excellent conductivity were grown on 3D flexible carbon fiber cloth (CFC) via hydrothermal and calcination methods to construct an efficient flexible glucose-sensitive detection electrode. For electrochemical-based sensors, high conductivity is a prerequisite for reliable data acquisition. To avoid the problems associated with using insulating Nafion or paraffin binders, we adopted a strategy of directly growing Mn-doped NiO onto the electrode surface, thereby avoiding interference due to the oxidization of species present in real samples at higher redox potentials, since Ni2+/Ni3+ has low redox potential. Therefore, the electrode has a linear range of 3-5166 µM for glucose detection, with a detection limit as low as 0.28 µM, showing excellent selectivity and reproducibility. The composite-modified electrode provides accurate detection results with real human serum samples, which are in full agreement with those of commercial blood glucose meters. In addition, we tested the glucose content in tea and sorghum fermentation broth at different stages, further expanding the application range of the Mn-NiO sensors. The nano-enzyme sensor fabricated herein offers a new idea for further integration into wearable flexible electronic devices for accurate glucose detection.

Sandwich-type microRNA biosensor based on graphene oxide incorporated 3D-flower-like MoS2 and AuNPs coupling with HRP enzyme signal amplification.

A sandwich electrochemical biosensing strategy for ultrasensitive detection of miRNA-21 was developed by using graphene oxide incorporated 3D-flower-like MoS2 (3D MoS2-rGO) nanocomposites as the substrate and horseradish peroxidase (HRP)-functionalized DNA strand 1 (S1)-gold nanoparticles (S1-AuNPs-HRP) as signal amplification probes. Herein, 3D MoS2-rGO nanocomposites not only had a large specific surface area and excellent conductivity, but also provided more attachment sites for electrodepositing AuNPs. In the presence of target miRNA, a sandwich structure was formed, and the determination of the miRNA-21 was carried out by measuring the DPV response of H2O2 mediated by hydroquinone (HQ) at a potential of + 0.052 V (vs AgCl reference electrode). Under the optimal experimental conditions, the as-prepared biosensor enabled the ultrasensitive detection of miRNA-21 from 5 fM to 0.5 µM with the low detection limit of 0.54 fM (S/N = 3), comparable or lower than previous reported methods for miRNA-21 detection, which benefited from the synergistic amplification of 3D MoS2-rGO and AuNPs-HRP. The prepared biosensor showed satisfactory selectivity, reproducibility, and stability towards miRNA-21 detection. The biosensor was feasible for accurate and quantitative detection of miRNA-21 in normal human serum samples with RSD below 5.86%, which showed a great potential in clinical analysis and disease diagnosis.

Compact TiO2@SnO2@C heterostructured particles as anode materials for sodium-ion batteries with improved volumetric capacity.

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage. Increasing the energy density of SIBs demands anode materials with high gravimetric and volumetric capacity. To overcome the drawback of low density of conventional nanosized or porous electrode materials, compact heterostructured particles are developed in this work with improved Na storage capacity by volume, which are composed of SnO2 nanoparticles loaded into nanoporous TiO2 followed by carbon coating. The resulted TiO2@SnO2@C (denoted as TSC) particles inherit the structural integrity of TiO2 and extra capacity contribution from SnO2, delivering a volumetric capacity of 393 mAh cm-3 notably higher than that of porous TiO2 and commercial hard carbon. The heterogeneous interface between TiO2 and SnO2 is believed to promote the charge transfer and facilitate the redox reactions in the compact heterogeneous particles. This work demonstrates a useful strategy for electrode materials with high volumetric capacity.

Amino-functionalized multilayer Ti3C2Tx enabled electrochemical sensor for simultaneous determination of Cd2+ and Pb2+ in food samples.

Herein, amino-functionalized multilayer titanium carbide (NH2-Ti3C2Tx) was developed and applied to electrochemical sensor for simultaneous determination of Cd2+ and Pb2+. The NH2-Ti3C2Tx was prepared by grafting (3-amino-propyl) triethylsilane (APTES) onto the surface of Ti3C2Tx. Its morphology, crystal structure and chemical composition were characterized by field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS). Benefiting from the unique multilayer structure, large active surface area, strong adsorption capacity and excellent electrical conductivity, the functionalized NH2-Ti3C2Tx presented satisfactory electrochemical performances for Cd2+ and Pb2+ determination, and the detection limits were 0.41 µg L-1 and 0.31 µg L-1, respectively. Based on chemical coordination and electrochemical accumulation, the suggested mechanism for Cd2+ and Pb2+ determination was also deeply clarified. Besides, it was successfully applied to simultaneous determination of Cd2+ and Pb2+ in food samples including rice, wheat, sorghum and corn, demonstrating a good practicability.

An ultrasensitive electrochemical biosensor for microRNA-21 detection via AuNPs/GAs and Y-shaped DNA dual-signal amplification strategy.

Herein, a gold nanoparticles/graphene aerogels (AuNPs/GAs) modified electrochemical biosensor with catalytic hairpin assembly (CHA) and Y-shaped DNA nanostructure dual-signal amplification approaches for ultrasensitive microRNA-21 (miR-21) detection was successfully constructed, which displayed an ultra-wide detection linear range from 5 fM to 50 nM, as well as a relatively low detection limit (LOD) of 14.70 aM (S/N = 3). Furthermore, the sensing strategy had excellent specificity among highly homologous miRNA family members and exhibited satisfactory analytical performance for miRNA detection.

Duplex-specific nuclease powered 3D DNA walker and quantum dots barcodes for homogeneous electrochemical detection of microRNAs.

Multiplex microRNAs (miRNAs) detection is beneficial for early diagnosis and prognosis of cancer. Herein, duplex-specific nuclease (DSN) powered 3D DNA walker and quantum dots (QDs) barcodes were designed for the simultaneous detection of miRNAs in a homogeneous electrochemical sensor. In the proof-of-concept experiment, the effective active area of the as-prepared graphene aerogel-modified carbon paper (CP-GAs) electrode was ∼14.30 times larger than that of the traditional glassy carbon electrode (GCE), endowing the enhanced capability of loading more metal ions for ultrasensitive detection of miRNAs. In addition, DSN-powered target recycling and DNA walking strategy assured the sensitive detection of miRNAs. After the introduction of magnetic beads (MNs) and electrochemical double enrichment strategies, the integration of triple signal amplification methods yielded good detection results. Under optimal conditions, towards simultaneous detection of microRNA-21 (miR-21) and miRNA-155 (miR-155), a linear range of 10-16-10-7 M and a sensitivity of 10 aM (miR-21) and 2.18 aM (miR-155) were achieved, respectively. It was worth mentioning that the prepared sensor can detect miR-155 down to 0.17 aM, which was also extremely advantageous among the sensors reported so far. What's more, through verification, the prepared sensor had good selectivity and reproducibility, and exhibited good detection ability in complex serum environments, showing great potential in early clinical diagnosis and screening.

Flexible carbon fiber cloth supports decorated with cerium metal- organic frameworks and multi-walled carbon nanotubes for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples.

The widespread heavy metal pollution endangers human health; hence, accurate on-site detection and quantification of heavy metal content in the surroundings is a vital step in reversing the harmful effect. Herein, an electrochemical sensor based on flexible cerium metal-organic framework@multi-walled carbon nanotubes/carbon cloth (CeMOF@MWCNTs/CC) was constructed for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples. The rich carboxyl groups of MWCNTs provided abundant sites for the adsorption of Cd2+ and Pb2+, and the mutual conversion of Ce3+ and Ce4+ in CeMOF facilitated the reduction and reoxidation of metal ions. The prepared electrode showed excellent performance in the simultaneous measurement of Cd2+ and Pb2+, with detection limits of 2.2 ppb and 0.64 ppb, respectively. More importantly, the sensing platform has been successfully used to detect simultaneously Cd2+ and Pb2+ in grain and water samples, and the detection results were consistent with the standard methods, showing great potential in environmental monitoring and food safety.

Metal-organic framework-derived porous ternary ZnCo2O4 nanoplate arrays grown on carbon cloth for simultaneous electrochemical determination of ascorbic acid, dopamine, and uric acid.

Metal-organic frameworks derived from ternary metal oxide directly grown on the conductive substrate have attracted great interest in electrochemical sensing. In this work, metal-organic framework-derived ternary ZnCo2O4 nanoplate arrays that were grown on carbon cloth (ZnCo2O4 NA/CC) are fabricated and applied for the electrochemical determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Field emission scanning electron microscope (FESEM) reveals that a network-like CC substrate is covered with considerable nanoplate arrays, presenting a large specific area. X-ray photoelectron spectroscopy (XPS) demonstrates the nanoplate arrays to be composed of ZnCo2O4. Benefiting from the unique array morphology and ternary element composition, the ZnCo2O4 NA/CC shows desirable performances for simultaneous detection of AA, DA, and UA. The individual detection limits are 7.14 µM for AA, 0.25 µM for DA, and 0.33 µM for UA. Additionally, the ZnCo2O4 NA/CC is successfully applied for the quantitative determination of AA, DA, and UA in spiked serum samples, showing its great application potential.

Mesoporous silicas tethered with anions as quasi-solid electrolytes for lithium-metal batteries.

Mesoporous silicas tethered with anions were developed as quasi-solid electrolytes for Li-metal batteries. The high grafted density of trifluoromethylsulfonyl (-NTf-) groups and their uniformly distributed negative charge endow MCM41-NLiTf with a room temperature single Li-ion conductivity of up to 2.4 × 10-4 S cm-1, which enables stable cycling of LFP‖Li batteries.

MXene-MoS2 heterostructure collaborated with catalyzed hairpin assembly for label-free electrochemical detection of microRNA-21.

Abnormal expression of microRNAs is greatly associated with the occurrence of various cancer types, revealing great potential of microRNA as biomarkers for cancer diagnosis and prognosis. Herein, a MXene-MoS2 heterostructure enhancing electrochemical biosensor coupled with catalytic hairpin assembly (CHA) amplification approach for label-free determination of microRNA-21 (miR-21) was successfully assembled. In particular, the unique micro-nano heterostructure with large specific area and favorable electroconductivity exhibited the ability of excellent confinement effect. Thus, rendered the MXene-MoS2 heterostructure the ability to trigger more target recycling reaction, giving new vitality to the traditional CHA amplification method. Meanwhile, thionine (Thi) and gold nanoparticles (AuNPs) were anchoring at the surface of MXene-MoS2 heterostructure, respectively, empowered the sensor the capability of capture probes fixation and miR-21 label-free determination. When numerous electronegative double-stranded DNA generated, the electron transfer was greatly hindered, resulting in signal decrease. Accordingly, the design denoted a broad dynamic range from 100 fM to 100 nM and a detection limit of about 26 fM, comparable or lower than previous reported methods for miR-21 detection. Furthermore, the sensing platform supplied satisfactory selectivity, reproducibility and stability towards the miR-21 detection. The real sample determination also showed a promising performance under clinical circumstance. Finally, from the clinical standpoint, the proposed biosensor is a considerable platform toward early disease detection and monitoring.

A novel electrochemical sensor for simultaneous detection of Cd2+ and Pb2+ by MXene aerogel-CuO/carbon cloth flexible electrode based on oxygen vacancy and bismuth film.

Herein, a novel MXene aerogel-CuO/carbon cloth (MXA-CuO/CC) electrochemical sensor was constructed, and the synergistic adsorption of heavy metal ions by oxygen vacancies and Bi (III) was investigated with Cd2+ and Pb2+ as detection targets. The oxygen vacancies of CuO have a strong affinity for heavy metal ions, which promoted the adsorption of Cd2+ and Pb2+ on the electrode surface. In addition, the introduced Bi (III) can form alloys with heavy metal ions, which effectively enhanced the adsorption capacity of sensing electrodes for Cd2+ and Pb2+. Differential pulse anodic stripping voltammetry (DPASV) was used to study the performance of MXA-CuO/CC sensitive electrode for the detection of Cd2+ and Pb2+ separately and simultaneously. The constructed sensing electrode has excellent detection performance, and can detect Cd2+ (4 µg L-1- 800 µg L-1) and Pb2+ (4 µg L-1- 1200 µg L-1) simultaneously with detection limits of 0.3 µg L-1 (Cd2+) and 0.2 µg L-1 (Pb2+), respectively. The proposed sensor electrode also has good anti-interference performance, excellent stability and reproducibility. It is worth mentioning that the proposed method can accurately detect Cd2+ and Pb2+ in food and water samples, which is consistent with the detection results of inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS).

Adaptive PCA based fault diagnosis scheme in imperial smelting process.

In this paper, an adaptive fault detection scheme based on a recursive principal component analysis (PCA) is proposed to deal with the problem of false alarm due to normal process changes in real process. Our further study is also dedicated to develop a fault isolation approach based on Generalized Likelihood Ratio (GLR) test and Singular Value Decomposition (SVD) which is one of general techniques of PCA, on which the off-set and scaling fault can be easily isolated with explicit off-set fault direction and scaling fault classification. The identification of off-set and scaling fault is also applied. The complete scheme of PCA-based fault diagnosis procedure is proposed. The proposed scheme is first applied to Imperial Smelting Process, and the results show that the proposed strategies can be able to mitigate false alarms and isolate faults efficiently.

Dietary exposure to aluminium of urban residents from cities in South China.

A dietary survey was conducted over three consecutive days by using 24-hour dietary recall in the Pearl River Delta of South China to investigate the dietary consumption status. A total of 1702 food samples, 22 food groups, were collected, and aluminium concentrations of foods were determined by using ICP-MS. Weekly dietary exposure to aluminium of the average urban residents of South China was estimated to be 1.5 mg kg⁻¹ body weight, which amounted to 76% of the provisional tolerable weekly intake. Wheat-made products (53.5%) contributed most to the dietary exposure, followed by vegetables (12.2%). The high-level consumers' weekly exposure to aluminium was 11.1 mg kg⁻¹ body weight, which amounted to 407% of the provisional tolerable weekly intake. The results indicated that the general urban residents in South China might be safe from aluminium exposure, but the high-level consumers might be at some risk of aluminium exposure. The foods contributing to aluminium exposure were processed food with aluminium-containing food additives. It is necessary to take effective measures to control the overuse of aluminium-containing food additives.