Pattern-based colorimetric sensor array chip for discrimination of Baijiu aromas

Gas mixtures are comprised of numerous complex components, making the accurate identification a continuing challenge due to the significant limitations of existing detection methods. Herein, we developed a low-cost and sensitive pattern-based colorimetric sensor array chip for the identification of typical gas mixtures - Baijiu aroma. Specifically, three nanomaterials (AuNPs, MoS2 and ZIF-8) were prepared to adsorb gas molecules and enhance the reaction of trace gases with sensor arrays. The colorimetric sensor array chip took only 5 min to complete the recognition of Baijiu aromas and effectively avoided recognition errors caused by sommelier olfactory fatigue. Notably, the hierarchical cluster analysis (HCA) revealed no confusion or errors in the results of 80 tests across the five trials involving 16 commercial Baijius. Even fake Baijius with similar ingredients could be easily identified, demonstrating the excellent analytical capabilities of the system in Baijiu identification and its significant potential for quality control of Baijius.

Sulfhydryl-functionalized 3D MXene-AuNPs enabled electrochemical sensors for the selective determination of Pb2+, Cu2+ and Hg2+ in grain

Herein, we made 3D MXene-AuNPs by in situ growth of gold nanoparticles (AuNPs) on the surface of MXene by chemical reduction method, and then introduced three sulfhydryl (-SH) compounds as functionalized modifiers attached to the AuNPs to form a highly selective composite material for the detection of Pb2+, Cu2+, and Hg2+, respectively. The doping of AuNPs changes the microstructure of 2D MXene and generates more active sites. On a sensing platform based on ITO array electrodes, the detection system was optimised with sensitivities up to 1.157, 0.846 and 0.799 μA·μg-1Lcm-2 (Pb2+, Cu2+, and Hg2+). The selectivity of MXene@AuNPs was effectively improved by sulfhydryl group modification. In the range of 1-1300 μg L-1, the detection limits of three ions were 0.07, 0.13 and 0.21 μg L-1. In addition, this method can efficiently and accurately detect heavy metal ions in four cereal samples with consistent results with inductively coupled plasma mass spectrometry.

A three-modal fluorescent sensor harnessing diverse luminescent mechanisms for the purpose of segmented Baijiu identification

The classification and verification of segmented Baijiu hold significant importance as they profoundly influence the blending and overall quality of the Baijiu. Our scholarly investigation yielded a fluorescent sensor with three luminescent modes by integrating Tb3+ and RHB into UiO-66. The interplay between carboxyl-containing compounds and RHB/Tb@TLU-2 orchestrates a harmonious molecular association, where the convergence of carboxyl groups with Tb3+ yields a resonating impact on the antenna effect of BDC-SO3-. Furthermore, the acidity and alkalinity of reactants induced a charge transfer interaction between BDC-NH2 and Zr4+ and led to structural changes in RHB/Tb@TLU-2, resulting in observable fluorescence signal variations across the three emission centers. The sensor array successfully identified eight organic acids, achieving an impressive 97.5 % accuracy in discerning segmented Baijiu samples from four Baijiu pits. This meticulous methodology prioritizes simplicity, swiftness, and effectiveness, paving the path for comprehensive segmented Baijiu analysis in the esteemed realm of Brewing production.

Label-free fluorescent sensor for sensitive detection of ctDNA based on water stabilized CsPbBr3 nanosheet

The detection of circulating tumor DNA (ctDNA), as a practical liquid biopsy technique, was of great significance for the study of cancer diagnosis and prognosis. However, reported methods for detection ctDNA still have some limitations, such as tedious process and high cost. In this study, CsPbBr3 nanosheet (CsPbBr3 NS) with high water stability was prepared by etching, and its fluorescence intensity could be stably stored for 1 year. The Ti3C2Tx possessed high quenching efficiency for CsPbBr3 NS and the HOMO-LUMO orbital study revealed that the PET mechanism was responsible for fluorescence quenching. And the Ti3C2Tx showed stronger affinity towards single-stranded DNA (ssDNA), as compared with double-stranded DNA (dsDNA). The probe ssDNA could be adsorbed on the surface of Ti3C2Tx through π-π stacking. After the targets were recognized by probe ssDNA to form dsDNA, its affinity with Ti3C2Tx decreased and the active site of Ti3C2Tx recovered, causing a high quenching efficiency on CsPbBr3 NS. Based on this, a label-free fluorescent biosensor was designed for the sensitive detection of ctDNA (EGFR 19 Dels for non-small cell lung cancer, NSCLC). Under the optimal experimental conditions, this biosensor exhibited a detection limit of 180 fM and a linear range of 50 pM-350 pM with amplification of magnetic beads through strand displacement reaction. In addition, this sensor was applied to the detection of ctDNA in serum samples and cells lysates. This method for ctDNA detection was expected to have great potential for biomarker detection in the field of liquid biopsy.

A novel colorimetric and fluorometric dual-signal identification of organics and Baijiu based on nanozymes with peroxidase-like activity

Nanozymes were nanomaterials with enzymatic properties. They had diverse functions, adjustable catalytic activity, high stability, and easy large-scale production, attracting interest in biosensing. However, nanozymes were scarcely applied in Baijiu identification. Herein, a colorimetric and fluorometric dual-signal determination mediated by a nanozyme-H2O2-TMB system was developed for the first time to identify organics and Baijiu. Since the diverse peroxidase-like activity of nanozymes, resulted in different degrees of oxidized TMB. Based on this, 21 organics were identified qualitatively and quantitatively by colorimetric method with a rapid response (<12 min), broad linearity (0.0005-35 mM), and low detection limits (a minimum of 30 nM for glutaric acids). Furthermore, the fluorometric method exhibited excellent potential for accurate determination of organics, with detection ranges of 2-200 µmol/L (LOD: 0.22 µmol/L) for l-ascorbic acid and 2-300 µmol/L (LOD: 0.59 µmol/L) for guaiacol. Finally, the sensor was successfully applied to identify fake Baijiu and Baijiu from 16 different brands.

A Novel CRISPR/Cas12a-Mediated Ratiometric Dual-Signal Electrochemical Biosensor for Ultrasensitive and Reliable Detection of Circulating Tumor Deoxyribonucleic Acid

Circulating tumor DNA (ctDNA) holds great promise as a noninvasive biomarker for cancer diagnosis, treatment, and prognosis. However, the accurate and specific quantification of low-abundance ctDNA in serum remains a significant challenge. This study introduced, for the first time, a novel exponential amplification reaction (EXPAR)-assisted CRISPR/Cas12a-mediated ratiometric dual-signal electrochemical biosensor for ultrasensitive and reliable detection of ctDNA. To implement the dual-signal strategy, a signal unit (ssDNA-MB@Fc/UiO-66-NH2) was prepared, consisting of methylene blue-modified ssDNA as the biogate to encapsulate ferrocene signal molecules within UiO-66-NH2 nanocarriers. The presence of target ctDNA KRAS triggered EXPAR amplification, generating numerous activators for Cas12a activation, resulting in the cleavage of ssDNA-P fully complementary to the ssDNA-MB biogate. Due to the inability to form a rigid structure dsDNA (ssDNA-MB/ssDNA-P), the separation of ssDNA-MB biogate from the UiO-66-NH2 surface was hindered by electrostatic interactions. Consequently, the supernatant collected after centrifugation exhibited either no or only a weak presence of Fc and MB signal molecules. Conversely, in the absence of the target ctDNA, the ssDNA-MB biogate was open, leading to the leakage of Fc signal molecules. This clever ratiometric strategy with Cas12a as the "connector", reflecting the concentration of ctDNA KRAS based on the ratio of the current intensities of the two electroactive signal molecules, enhanced detection sensitivity by at least 60-300 times compared to single-signal strategies. Moreover, this strategy demonstrated satisfactory performance in ctDNA detection in complex human serum, highlighting its potential for cancer diagnosis.

A wearable flexible electrochemical biosensor with CuNi-MOF@rGO modification for simultaneous detection of uric acid and dopamine in sweat

BACKGROUND

In health assessment and personalized medical services, accurate detection of biological markers such as dopamine (DA) and uric acid (UA) in sweat is crucial for providing valuable physiological information. However, there are challenges in detecting sweat biomarkers due to their low concentrations, variations in sweat yield among individuals, and the need for efficient sweat collection.

RESULTS

We synthesized CuNi-MOF@rGO as a high-activity electrocatalyst and investigated its feasibility and electrochemical mechanism for simultaneously detecting low-concentration biomarkers UA and DA. Interaction between the non-coordinating carboxylate group and the sample produces effective separation signals for DA and UA. The wearable biomimetic biosensor has a wide linear range of 1-500 μM, with a detection limit of 9.41 μM and sensitivity of 0.019 μA μM-1 cm-2 for DA, and 10-1000 μM, with a detection limit of 9.09 μM and sensitivity of 0.026 μA μM-1 cm-2 for UA. Thus, our sensor performs excellently in detecting low-concentration biomarkers. To improve sweat collection, we designed a microfluidic-controlled device with hydrophilic modification in the microchannel. Experimental results show optimal ink flow at 2% concentration. Overall, we developed an innovative and highly active electrocatalyst, successfully enabling simultaneous detection of low-concentration biomarkers UA and DA.

SIGNIFICANCE

This study provides a strategy for sweat analysis and health monitoring. Moreover, the sensor also showed good performance in detecting real sweat samples. This study has shown great potential in future advances in sweat analysis and health monitoring.

Wearable electrochemical patch based on iron nano-catalysts incorporated laser-induced graphene for sweat metabolites detection

The development of wearable devices shows great application potential in health management. In this work, we propose the fabrication of a novel wearable electrochemical patch and prove its application in sweat metabolites detection. The patch is developed based on iron nano-catalysts incorporated laser-induced graphene (FeNCs/LIG), which is a newly integrated sensing electrode with unique three-dimensional nanostructure and good electrocatalytic activity. It shows desirable sensing performances for sweat metabolites including tyrosine (Tyr) and uric acid (UA) molecules. The detection limit of Tyr and UA can reach 5.11 μM and 1.37 μM, respectively. Besides, density functional theory calculation deeply reveals that the Fe active sites of FeNCs play an important role in molecule adsorption and electron transference, thus promoting sensing performance. To realize wearable application, a dual-channel hydrogel chip is designed and assembled with FeNCs/LIG. The developed patch is successfully utilized to accurately determination of Tyr and UA in sweat. This work is expected to provide a new non-invasive strategy for evaluating amino acid intake and metabolic level.

A novel electrochemical strategy based on MXene@rGO composite aerogel-doped UiO-66-NH2 for simultaneous detection of cadmium and lead in grain and water samples

Herein, a novel electrochemical sensing platform is designed for the simultaneous detection of Cd2+ and Pb2+, using MXene@rGO composite aerogel-doped UiO-66-NH2. The MXene@rGO composite aerogel not only serves as the support structure for UiO-66-NH2, but also improves the conductivity of the composite by accelerating the electron transport in the matrix. The amino group of UiO-66-NH2 offers binding sites for heavy-metal ions, and the existence of PhNH2/PhNH3+ in the composite promotes the redox processes of the metal ions to be detected on the electrode surface. The proposed sensing strategy can detect Cd2+ and Pb2+ independently and concurrently, with detection limits of 0.46 ppb and 0.40 ppb, respectively. Remarkably, when this strategy is used for simultaneous detection of Cd2+ and Pb2+ in grain and water samples, it exhibits excellent accuracy and reliability, aligning with the standard method (e.g., AAS and ICP-MS) demonstrating considerable promise in practical applications.

Fe Single-Atom Carbon Dots Nanozyme Collaborated with Nucleic Acid Exonuclease III-Driven DNA Walker Cascade Amplification Strategy for Circulating Tumor DNA Detection

Circulating tumor DNA (ctDNA), as a next-generation tumor marker, enables early screening and monitoring of cancer through noninvasive testing. Exploring the development of new methods for ctDNA detection is an intriguing study. In this work, a unique electrochemical biosensor for the ctDNA detector was constructed in the first utilizing Fe single-atom nanozymes-carbon dots (SA Fe-CDs) as a signaling carrier in collaboration with a DNA walker cascade amplification strategy triggered by nucleic acid exonuclease III (Exo III). The electrochemical active surface area of AuNPs/rGO modified onto a glassy carbon electrode (AuNPs/rGO/GCE) was about 1.43 times that of a bare electrode (bare GCE), with good electrical conductivity alongside a high heterogeneous electron transfer rate (5.81 × 10-3 cm s-1), that is, as well as the ability to load more molecules. Sequentially, the DNA walker cascade amplification strategy driven by Exo III effectively converted the target ctDNA into an amplified biosignal, ensuring the sensitivity and specificity of ctDNA. Ultimately, the electrochemical signal was further amplified by introducing SA Fe-CDs nanozymes, which could serve as catalysts for 3,3',5,5'-tetramethylbenzidine (TMB) oxidation with facile responding (Vmax = 0.854 × 10-6 M s-1) and robust annexation (Km = 0.0069 mM). The integration of the triple signal amplification approach achieved detection limits as low as 1.26 aM (S/N = 3) for a linearity spanning from 5 aM to 50 nM. In this regard, our proposal for a biosensor with exceptional assay properties in complicated serum environments had great potential for early and timely diagnosis of cancer.

A dual-functional single-atom Fe nanozyme-based sensitive colorimetric sensor for tannins quantification in brandy

Traditional methods of tannins detection suffer from complex pretreatment, long detection time, and limited sensitivity. Modern techniques like liquid chromatography require expertise, involve tedious result processing, and lack effective data visualization. Therefore, there is a need for an alternative detection method that simplifies pretreatment and detection steps, reduces analysis time, and provides visualized results. In this study, a novel colorimetric sensor based on single-atom Fe nanozyme (Fe@CN-20) was developed for tannins detection. Fe@CN-20 exhibited laccase-like and oxidase-like activities, enabling simultaneous oxidation of tannins and a substrate called TMB. Tannins competed with TMB, allowing quantification of tannins content. The Fe@CN-20/TMB system provided a detection range of 5-100 mg/L tannic acid, with a detection limit of 0.13 mg/L (S/N = 3). Analysis time was approximately 30 min. The platform successfully quantified tannins in brandy, showing less than 5% deviation compared to the standard method. The sensor was simple, sensitive, rapid, and provided strong visualization.

Ultra-sensitive electrochemical sensors through self-assembled MOF composites for the simultaneous detection of multiple heavy metal ions in food samples

Using an assemble-able MOF material, we successfully constructed an ultra-sensitive electrochemical sensor based on Bi2CuO4@Al-MOF@UiO-67 nanocomposite material, in order to investigate the adsorption properties of the Bi2CuO4@Al-MOF@UiO-67 functional material on the heavy metal ion. The Cd2+, Cu2+, Pb2+ and Hg2+ can be detected at the same time. Selective recognition and enrichment of various metal ions on different substrates can be achieved through the assembly of a large number of Al-MOF and UiO-67-MOF nanomaterial composites with small particle sizes on the Bi2CuO4 surface. Based on this, a new type of sensor is researched and prepared, which has been shown to have good stability and reproducibility. Due to its unique assembly structure, large active surface area, excellent adsorption capacity, and high electrical conductivity, Bi2CuO4@Al-MOF@UiO-67 presents outstanding performance. In addition, the sensor also exhibits excellent electrocatalytic redox capacity and high selectivity. The adsorption capacity of Cd2+, Cu2+, Pb2+ and Hg2+ is also significantly improved under the action of the sensor electrode, however, this is not the case. The limits of detection for Cd2+, Cu2+, Pb2+ and Hg2+ were found to be 0.02 pM, 0.032 pM, 0.018 pM and 0.041 pM, respectively. In order to investigate the detection mechanism of Cd2+, Cu2+, Pb2+ and Hg2+ was adsorption properties as well as electrochemical accumulation of Bi2CuO4@Al-MOF@UiO-67 on the metal atoms were investigated. This method has been successfully applied to samples of rice, sorghum, maize, milk, honey, and tea, and has enabled the simultaneous detection of Cd2+, Cu2+, Pb2+ and Hg2+, which is of significant practical value.

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Eu-MOF based fluorescence probe for ratiometric and visualization detection of Cu2

Water contamination caused by heavy metals represents an urgent global issue. Cu2+, a potential trace heavy metal pollutant, can accumulate in the human body through the food chain, leading to excessive levels that give rise to diverse health complications. Hence, in this investigation, a novel and efficacious fluorescent probe named Eu-BTB was developed for the detection of Cu2+, employing 1,3,5-triphenyl(4-carboxyphenyl) (H3BTB) as the ligand and Eu3+ as the metallic framework. The probe demonstrates exceptional fluorescence characteristics. The interaction between the probe ligand BTB and Eu3+ triggers an antenna effect, heightening the emission efficiency of Eu3+ while preserving its intrinsic emission. The introduction of Cu2+ competes with BTB for binding, thus quelling the antenna effect and inducing a fluorescence alteration. Within the concentration range of 0.05-10 μM, the fluorescence intensity-to-Cu2+ concentration ratio exhibits a robust linear correlation, with a remarkably low detection limit of 10 nM and a rapid response time of 3 min. The fluorescent probe has been effectively deployed for the detection of copper ions in water across diverse environmental conditions, with the obtained outcomes being validated via the conventional approach of inductively coupled plasma mass spectrometry (ICP-MS). The Eu-BTB probe showcases the advantages of simplicity, swiftness, and broad applicability, thus affirming its potential for the prompt and accurate detection of Cu2+ in diverse environmental water samples.

Hybridization chain reaction circuit controller: CRISPR/Cas12a conversion amplifier for miRNA-21 sensitive detection

MicroRNA (miRNA) is crucial to the diagnose of various diseases. However, the accurate detection of miRNA has been challenging due to its short length and low abundance. Here, we designed a hybridization chain reaction (HCR) circuit controller to initiate the CRISPR/Cas12a conversion amplifier (HCR-Cas12a controller) for sensitive detection of miRNA-21 (miR-21). In the HCR, pre-crRNA was encapsulated in a hairpin structure until the miR-21 was present. Afterward, Cas12a fully exerted its RNase activity to self-mature pre-crRNA. Then, the trans-cleavage activity of Cas12a was initiated by activator. This results in the conversion of biological signals to fluorescent signal. During HCR-Cas12a controller, the circuit formed quickly, while the Cas12a system worked in a short time. The miR-21 was ultra-sensitively detected with the wide detection range of 1 fM - 100 nM, and the calculated limit of detection was 75.4 aM. The sensitivity was an order of magnitude lower than the standard method. The formation of HCR at room temperature does not require a thermal cycler. Additionally, Cas12a can work without the need for precise or expensive instruments. Therefore, our proposed method was suitable for low-resource settings, and provided a technical basis for sensitive detection of miRNA in low concentration range.

Completely Free from PAM Limitations: Asymmetric RPA with CRISPR/Cas12a for Nucleic Acid Assays

Experimentally, Cas12a can recognize multiple protospacer adjacent motif (PAM) sequences and is not restricted to the "TTTN". However, the application of the CRISPR/Cas12a system is still limited by the PAM for double-stranded DNA (dsDNA). Here, we developed asymmetric RPA (Asy-RPA) to completely break the limitations of PAM. Asy-RPA not only achieved efficient amplification but also converted dsDNA to single-stranded DNA (ssDNA) without complicated steps. The ssDNA products activated the trans-cleavage activity of Cas12a, outputting signals. The application of Asy-RPA completely freed Cas12a from the PAM, which can be more widely used in nucleic acid detection, such as lumpy skin disease virus, with an actual detection limit as low as 1.21 × 101 copies·μL-1. More importantly, Cas12a was intolerant to mutations on ssDNA. This provided technical support for the detection and identification of wild-type Mycobacterium tuberculosis (WT-TB) and rifampin-resistant mutant-type M. tuberculosis (MT-TB). The detection limit was as low as 1 fM for 1% mixed samples. The detection and availability of different treatment options for treatment-resistant and WT-TB were significant for the elimination of TB. In summary, the platform consisting of Asy-RPA and CRISPR/Cas12a was suitable for the detection of various viruses and bacteria and was a boon for the detection of dsDNA without recognizable PAM.

A portable sensor for glucose detection in Huangshui based on blossom-shaped bimetallic organic framework loaded with silver nanoparticles combined with machine learning

In this work, we propose a blossom-like Ni, Co bimetallic metal-organic framework (NiCo-MOF) synthesized hydrothermally and decorated with silver nanoparticles (AgNPs) via chemical reduction for electrochemical enzyme-free glucose sensing. The NiCo-MOF nanostructures had large specific surface area and good sensing performance. The AgNPs enhanced the electrochemical performance of the MOF, resulting in excellent electrochemical activity. The sensor exhibited sensitivities of 1191.84 and 271.19 μA mM-1 cm-2 in the linear ranges of 0.005-1.125 and 1.525-5.325 mM, respectively, with a detection limit of 2.3 μM. The sensor was successfully applied for glucose determination in Huangshui (HS) using an artificial neural network as machine learning (ML) model. The R2 value near 1, low RMSE, and high RPD values of the proposed ML model demonstrate its excellent fitting and prediction performance. This will provide a fast and portable intelligent sensing analysis technology for the detection of glucose in HS.

An ultrasensitive ratiometric electrochemical aptasensor based on metal-organic frameworks and nanoflower-like Bi2CuO4 for human epidermal growth factor receptor 2 detection

An ultra-sensitive ratiometric electrochemical aptasensor was constructed based on metal-organic frameworks (MOFs) and bimetallic oxides for the detection of the human epidermal growth factor receptor 2 (HER2), a breast cancer marker. The aluminum metal-organic framework (Al-MOF) and cerium-metal-organic framework (Ce-MOF) have higher specific surface area, which is conducive to load more aptamers or complementary DNA (cDNA), and realize the amplification of internal reference signal Fc. Furthermore, nanoflower-like bismuth copper oxide (Bi2CuO4) with abundant active sites was introduced to modify more aptamers on its surface, which were then fixed to the glassy carbon electrode (GCE) to amplify the detection signal. The quantitative detection of HER2 was achieved by differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The materials were characterized by scanning electron microscope, transmission electron microscope, Zeta potential analyzer, X-ray diffraction and X-ray photoelectron spectroscopy. The ratiometric electrochemical aptasensor based on nanomaterial and chain displacement signal amplification technology could discern HER2 in a very wide range (0.001-20.0 ng/mL) with an extremely low detection limit (0.049 pg/mL) and has demonstrated good performance in clinical serum analysis. This strategy also provides a feasible idea for sensitive analysis of other clinical tumor markers.

Microswimmer-Assisted Dual-Signal Sensor for Multiple Targets in Whole Blood

Accurate detection of biomarkers in whole blood is an important aspect of diagnostic testing but remains a challenge due to various interferences. However, using a self-calibrating two-signal strategy offers a solution that can overcome interference caused by experimental and environmental factors. Here, we proposed a novel microswimmer {methylene blue (MB)@ZIF-90@aptamer-HER2/3,3',5,5'-tetramethylbenzidine (TMB)@ZIF-90@aptamer-ER}-dual-signal (electrochemical and fluorescence) homogeneous sensor based on functionalized ZIF nanomaterials for one-step simultaneous detection of human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) in whole blood. The proposed one-step ZIF-90 synthesis encapsulates TMB and MB with dual-signal properties. HER2 and ER aptamers adsorbed on MB@ZIF-90/TMB@ZIF-90 function as the gate switches. The microswimmer targets the HER2 and ER with adenosine triphosphate (ATP)-driven motion. When targets are present, aptamers dissociate and reduce the microswimmer's surface negative charge. The microswimmer undergoes attack and decomposition by swimming ATP due to the strong coordination force between ATP and Zn2+, leading to the release of MB and TMB. The negative charges on the surface of indium tin oxide enrich MB and TMB with positive charges, thereby increasing the intensities of electrochemical and fluorescence signals. The detection process was completed within 40 min, and the detection limits for ER and HER2 were 8.1 and 5.7 fg/mL respectively, with a linear range of 0.25-20 pg/mL.

Identification of Chinese baijiu from the same brand based on a graphene quantum dots fluorescence sensing array

The identification of Chinese baijiu is crucial to regulating the international market and maintaining legitimate rights, as the popularity, influence and awareness of baijiu are growing. A graphene quantum dot (GQD) based fluorescence sensor array is designed in this paper. Upon using only GQDs as a single sensing element, combining three different solvents improves the sensing array's detection sensitivity while simplifying material preparation and experimental detection. Adding organic substances creates intermolecular forces between the GQDs and the solvent, causing the fluorescence intensity to change. The sensor array was able to distinguish 21 types of organic matter, different ratios of quaternary mixed organic materials and 17 types of baijiu of the same brand. It also showed excellent performance in the detection of species in blind samples, with the machine learning algorithm successfully distinguishing baijiu from five other distilled spirits. The experiment provides guidance for the practical application of GQDs and provides a simple but effective reference for sensor arrays to detect baijiu.

Field-friendly and ultra-fast detection platform without nucleic acid extraction for virus detection

The polymeric chain reaction (PCR) has come under fire for being time-consuming, requiring expensive equipments, and requiring the extraction and purification of nucleic acids. Here, an ultra-fast and sensitive detection platform without nucleic acid extraction solved the above problems. Firstly, the RoomTemp Sample Lysis Kit released the nucleic acid in 3 min and removed the inhibition to facilitate the amplification reaction. What's more, ultra-fast PCR (UF-PCR) can complete 40 cycles in just 15 min and 50 s. To improve the sensitivity and provide more convenient reading modes, CRISPR/Cas12a was mediated to detect Lumpy skin disease virus (LSDV). The platform output fluorescence and Lateral flow dipstick (LFD) signals. The actual detection limit was 2 × 101 copies·μL-1. The portable platform realized visualization, excellent sensitivity and quick speed. In summary, the field-friendly testing platform had great potential in practical testing.

A PVDF-based colorimetric sensor array for noninvasive detection of multiple disease-related volatile organic compounds

Detection of human-generated volatile organic compounds (VOCs) is a new pathway for assessing health. Herein, a polyvinylidene fluoride (PVDF)-based colorimetric sensor array was designed for detecting disease-related VOCs (DVOCs) within 15 min, using a complex of Cu metal-organic framework, graphene aerogel, and dyes as response materials. Fingermaps derived from 28 DVOCs were obtained for further data processing. Pattern recognition was successfully employed in the correct discrimination of 28 DVOCs in low (10 μM), medium (100 μM), and high (300 μM) concentrations. Importantly, the sensor array also presented excellent discrimination ability and application potential when detecting VOCs produced by human cancer and normal cells. In general, VOC acquisition is noninvasive and harmless, and the PVDF-based sensor arrays are simple and visual. Such advantages expand their further application potential.

CRISPR/Cas12a and primer-assisted rolling circle amplification integrated ultra-sensitive dual-signal sensing platform for EGFR 19 detection

Herein, we integrated CRISPR/Cas12a with primer-assisted rolling circle amplification (PARCA) to specifically detect EGFR 19 from the genome. We fused the method into fluorescent and electrochemical detection systems forming a stable and sensitive dual-signal sensing platform. The fluorescent detection system stably detected EGFR 19 in a linear range from 500 fM to 10 nM with an ultra-low background signal. The electrochemical detection system possessed a detection limit as low as 42 aM due to the introduction of nanomaterial UIO-66-NH2. The dual-signal sensing platform showed superior performance in complex serum samples and real cell genomes and provided a flexible and dynamic approach for the ultra-sensitive detection of EGFR 19.

Synthesis of N,Si co-doped carbon dots to establish a fluorescent sensor for Hg(II) detection with triple signal output

Mercury is a heavy metal with extreme toxicity. Thus, it is of significance to develop an effective method for mercury ion detection with high performance. In this study, carbon dots doped with nitrogen and silicon (N,Si/CQDs) were successfully prepared from folic acid and N-[3-(trimethoxysily)propyl]-ethylenediamine. The N,Si/CQDs show an obvious cyan fluorescence of 460 nm with the radiation of 350 nm. The existence of mercury ions induces the fluorescence quenching of N,Si/CQDs due to photoinduced electron transfer, which was applied for the sensitive sensing of Hg(II). More importantly, the practical application of the N,Si/CQD probe was confirmed by measurements of Hg(II) in real samples of lake water, sorghum and rice. In addition, the N,Si/CQD nanoprobe was integrated on a sensing strip for specific detection of Hg(II). Quantitative measurement of Hg(II) was realized by the outstanding linearity between the diameter (or fluorescence intensity) of the fluorescence quenching ring and the concentration of mercury ions. The sensor shows potential for rapid detection with a triple signal readout on-site and represents a larger step towards practical applications.

Target-mediated rolling circle transcription coupling with CRISPR/Cas12a-Cas13a for simultaneous detection of HPV16 and HPV18

Simultaneous detection of multiple targets can provide important data support for clinical diagnosis and treatment. Here, we report a facile isothermal assay based on target-mediated rolling circle transcription coupling with CRISPR/Cas12a-Cas13a (TM-RCT/Cas12a-Cas13a). Through facile one-step amplification (TM-RCT), two target DNAs are converted to RNA amplified products. The simultaneous detection of HPV16 and HPV18 is then achieved by combining two CRISPR/Cas systems. This system shows excellent sensing performance and provides a universal method for simultaneous detection.

3D DNAzyme walker based electrochemical biosensor for attomolar level microRNA-155 detection

Herein, an ultrasensitive electrochemical biosensor for microRNA-155 (miR-155) detection based on the powerful catalytic and continuous walking signal amplification capability of 3D DNAzyme walker and the gold nanoparticles/graphene aerogels carbon fiber paper-based (AuNPs/GAs/CFP) flexible sensing electrode with excellent electrochemical performance was successfully constructed. In a proof-of-concept experiment, in the presence of miR-155, the DNAzyme strands anchored on the streptavidin-modified magnetic beads (MBs) silenced by locked strands can be activated, thus generating the walking arm of the 3D DNAzyme walker. Meanwhile, the substrate strands modified with Fe-MOF-NH2 nanoparticles were evenly distributed on the surface of MBs and served as tracks of the 3D DNAzyme walker. Once the DNAzyme strand was activated, the catalytic site in the substrate strand can be cleaved in the presence of Mn2+, and a large number of stumps modified with Fe-MOF-NH2 nanoparticles (output@Fe-MOF-NH2) will be generated during the continuous and efficient walking cleavage of the DNAzyme walker, driving the recognition-catalysis-release cycle process for signal amplification. Immediately afterwards, the signal was read out through the base complementary pairing of capture probe (PS) immobilized on the surface of the paper-based flexible sensing electrode AuNPs/GAs/CFP and signal probes output@Fe-MOF-NH2, thus achieving the quantitative detection of miR-155. Under optimal experimental conditions, the designed 3D DNAzyme walker-based biosensor exhibited a relatively lower limit of detection (LOD) of 56.23 aM, with a linear range of 100 aM to 100 nM. Overall, the proposed 3D DNAzyme walker biosensor exhibited good interference and reproducibility, demonstrating a promising future in the field of clinical disease diagnosis.

A label-free fluorescent sensor for rapid and sensitive detection of ctDNA based on fluorescent PDA nanoparticles

Technological advances in the detection of circulating tumor DNA (ctDNA) have made new options available for diagnosis, classification, biological studies, and treatment selection. However, effective and practical methods for analyzing this emerging class of biomarkers are still lacking. In this work, a fluorescent biosensor was designed for the label-free detection of ctDNA (EGFR 19 del for non-small cell lung cancer, NSCLC). The biosensor was based on the fact that MnO2 nanosheets (MnO2 NSs) have stronger affinity towards single-stranded DNA (ssDNA), as compared with double-stranded DNA (dsDNA). As a high-performance nanoenzyme, MnO2 NSs could oxidize dopamine (DA) into fluorescent polydopamine nanoparticles (FL-PDA NPs), which could be used as a fluorescence signal. The probe ssDNA could be adsorbed on the surface of MnO2 NSs through π-π stacking, and the active site would be masked, causing a lower fluorescence. After the targets were recognized by probe ssDNA to form dsDNA, its affinity for MnO2 NSs decreased and the active site recovered, causing a restored fluorescence. It was verified that Mn ions, •OH radicals and electron transfer were the important factors in the catalytic oxidation of DA. Under the optimal experimental conditions, this biosensor exhibited a detection limit of 380 pM and a linear range of 25-125 nM, providing reliable readout in a short time (45 min). This sensor exhibited outstanding specificity, stability and reproducibility. In addition, this sensor was applied to the detection of ctDNA in serum samples and cell lysates. It is demonstrated that FL-PDA NPs can be used as a fluorescence signal for easy, rapid and label-free detection of ctDNA without any other amplification strategies, and the proposed strategy has great potential for biomarker detection in the field of liquid biopsy.

Fe Single-Atom Nanozyme-Modified Wearable Hydrogel Patch for Precise Analysis of Uric Acid at Rest

Resting sweat analysis could provide unique insight into the metabolic levels of physiological and pathological states. However, the low secretion rate of resting sweat and the low concentration of metabolic molecules pose challenges for the development of noninvasive wearable sensors. Here, we demonstrated a wearable patch for the precise analysis of uric acid at rest. Fe single-atom nanozymes (FeSAs) with excellent electrocatalytic activity were used to develop a sensor for selective catalysis of uric acid (UA, 1-425 μM), and the catalytic mechanism of UA was later explored by density functional theory. In addition, polyaniline was integrated into the wearable patch for pH detection; thus, accurate analysis of sweat UA molecules can be achieved by pH calibration. Then, we explored the possibility of collecting resting sweat with different ratios of agarose hydrogels to reduce the sweat accumulation time. Finally, the possibility of a wearable patch for accurate UA detection in volunteer sweat samples was experimentally verified. We believe that our work provides novel insights and ideas for the analysis of resting sweat using wearable devices, further driving advancements in the field of personalized medicine.

CRISPR/Cas12a-Powered EC/FL Dual-Mode Controlled-Release Homogeneous Biosensor for Ultrasensitive and Cross-Validated Detection of Messenger Ribonucleic Acid

Accurate detection of cancer-associated mRNAs is beneficial to early diagnosis and potential treatment of cancer. Herein, for the first time, we developed a novel CRISPR/Cas12a-powered electrochemical/fluorescent (EC/FL) dual-mode controlled-release homogeneous biosensor for mRNA detection. A functionalized ssDNA P2-capped Fe3O4-NH2 loaded with methylene blue (P2@MB-Fe3O4-NH2) was synthesized as the signal probe, while survivin mRNA was chosen as the target RNA. In the presence of the target mRNA, the nicking endonuclease-mediated rolling circle amplification (NEM-RCA) was triggered to produce significant amounts of ssDNA, activating the collateral activity of Cas12a toward the surrounding single-stranded DNA. Thus, the ssDNA P1 completely complementary to ssDNA P2 was cleaved, resulting in that the ssDNA P2 bio-gate on Fe3O4-NH2 could not be opened due to electrostatic interactions. As a result, there was no or only a little MB in the supernatant after magnetic separation, and the measured EC/FL signal was exceedingly weak. On the contrary, the ssDNA P2 bio-gate was opened, enabling MB to be released into the supernatant, and generating an obvious EC/FL signal. Benefiting from the accuracy of EC/FL dual-mode cross-verification, high amplification efficiency, high specificity of NEM-RCA and CRISPR/Cas12a, and high loading of mesoporous Fe3O4-NH2 on signal molecules, the strategy shows aM-level sensitivity and single-base mismatch specificity. More importantly, the practical applicability of this dual-mode strategy was confirmed by mRNA quantification in complex serum environments and tumor cell lysates, providing a new way for developing a powerful disease diagnosis tool.

An ultrasensitive label-free fluorescent aptamer sensor based on pH-gated release coumarin for detect HER2

Evaluation of human epidermal growth factor receptor 2 (HER2) molecular markers is a very suitable option for early diagnosis of breast cancer. Metal-organic frameworks (MOFs) have large porosity and surface interactions such as π-π stacking, electrostatics, hydrogen bonding, and coordination. Here, we integrated the HER2 aptamer and fluorescent probe coumarin (COU) with zeolite imidazolic acid framework-8 (ZIF-8) to construct a label-free fluorescent aptamer sensor with pH-gated release of COU. In the presence of the target-HER2, the aptamer adsorbed on the surface of ZIF-8@COU specifically recognizes and falls off the HER2 protein, exposing a portion of the pore size of ZIF-8@COU while reducing the negative charge on the sensor surface, under alkaline hydrolysis conditions, a large number of COU fluorescent molecules can be produced and released in the detection system.The aptamer fluorescence sensor has good detection performance, sensitivity and low background interference, the detection linearity range of HER2 protein is 0.05-10 ng/mL, the detection limit is 0.0005 ng/mL, and it has good recovery rate for the serum detection of clinical breast cancer patients. Therefore, this sensor has high potential in detecting and monitoring HER2 levels for the care and clinical diagnosis of breast cancer patients.

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.

Multiple accurate and sensitive arrays for Capripoxvirus (CaPV) differentiation

Capripoxvirus (CaPV) contains three viruses that have caused massive losses in the livestock and dairy industries. Accurate CaPV differentiation has far-reaching implications for effectively controlling outbreaks. However, it has a great challenge to distinguishing three viruses due to high homology of 97%. Here, we established a sensitive CRISPR/Cas12a array based on Multiple-recombinase polymerase amplification (M-RPA) for CaPV differentiation, which provided a more comprehensive and accurate differentiation mode targeting VARV B22R and RPO30 genes. By sensitive CRISPR/Cas12a and M-RPA, the actual detection limits of three viruses were as low as 50, 40 and 60 copies, respectively. Moreover, Lateral flow dipstick (LFD) array based on CRISPR/Cas12a achieved portable and intuitive detection, making it suitable for point-of-care testing. Therefore, CRISPR/Cas12a array and LFD array paved the way for CaPV differentiation in practice. Additionally, we constructed a real-time quantitative PCR (qPCR) array to fill the qPCR technical gap in differentiation and to facilitate the quarantine departments.

Pattern-recognizing-assisted detection of mildewed wheat by Dyes/Dyes-Cu-MOF paper-based colorimetric sensor array

In order to timely discriminate wheat with different mildew rates, a Dyes/Dyes-Cu-MOF paper-based colorimetric sensor array was designed. Using array points to capture volatile gases of wheat with different mildew rates, and output RGB values. The correlation between ΔR/ΔG/ΔB values and odor components was established. The ΔG values of array points 2' and 3' showed the best correlation with mildew rate, with R² of 0.9816 and 0.9642. The ΔR value of 3 and the ΔG value of 2 correlate well with the mildew rate, with R² of 0.9625 and 0.9502, respectively. Then, the ΔRGB values are subjected to pattern recognition processing, and LDA achieves 100% correct discrimination for all samples, or divides high and low mildew areas. This method provides an odor-based monitoring tool for fast, visual and nondestructive evaluation of food safety and quality through visualization of odors produced by different mildew rates.

Highly sensitive and facile microRNA detection based on target triggered exponential rolling-circle amplification coupling with CRISPR/Cas12a

MicroRNAs (miRNAs) play a crucial role in the regulation of gene expression and have been implicated in many diseases. Herein, we develop a target triggered exponential rolling-circle amplification coupling with CRISPR/Cas12a (T-ERCA/Cas12a) system, which can achieve the ultrasensitive detection with simple operation and no annealing procedure. In this assay, T-ERCA combines the exponential amplification with rolling-circle amplification by introducing a dumb-bell probe with two enzyme recognition sites. miRNA-155 targets are activators that trigger exponential rolling circle amplification to produce large amounts of ssDNA, which is then recognized by CRISPR/Cas12a for further amplification. Compared with single EXPAR or RCA combined with CRISPR/Cas12a, this assay shows higher amplification efficiency. Therefore, benefiting from the excellent amplification effect of T-ERCA and the high recognition specificity of CRISPR/Cas12a, the proposed strategy shows a wide detection range from 1 fM to 5 nM with a LOD (limit of detection) down to 0.31 fM. Moreover, it shows good application ability for assessing miRNA levels in different cells, indicating that the T-ERCA/Cas12a may provide a new guidance for molecular diagnosis and clinical practical application.

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.

The End of the Gray Zone: One-Tube Nested Recombinase Polymerase Amplification with Ultrahigh Signal-to-Noise Ratio for Precisely Detecting and Surveilling Viruses

The samples were difficult to accurately determine positive or negative between 35 and 40 cycles by real-time quantitative PCR (qPCR) as the standard method. Here, we developed one-tube nested recombinase polymerase amplification (ONRPA) technology with CRISPR/Cas12a to overcome this difficulty. ONRPA broke the amplification plateau to substantially enhance the signals, which considerably improved the sensitivity and eliminated the problem of gray area. Using two pairs of primers one after another, it improved precision by lowering the probability of magnifying several target zones, which was completely free of contamination by nonspecific amplification. This was important in nucleic acid testing. Finally, by the CRISPR/Cas12a system as a terminal output, the approach achieved a high signal output as few as 2.169 copies·μL^-1 in 32 min. ONRPA was 100-fold more sensitive than conventional RPA and 1000-fold compared to qPCR. ONRPA coupled with CRISPR/Cas12a will be an important and new promoter of RPA in clinical applications.

Chaetocin exhibits anticancer effects in esophageal squamous cell carcinoma via activation of Hippo pathway

Dysfunction of the Hippo pathway is common in esophageal squamous carcinoma (ESCC). Chaetocin, a small molecular compound isolated from the marine fungus, exhibits potent anticancer effects. However, the anticancer effects of chaetocin on ESCC and its potential relationship to Hippo pathway remain unclear. Here, we demonstrated that chaetocin dramatically inhibited the proliferation in ESCC cells by causing cycle arrest in the M phase and activating the caspase-dependent apoptosis signaling pathway in vitro, and we also found that chaetocin induced the accumulation cellular reactive oxygen species (ROS). The RNA-seq analysis indicated that the Hippo pathway is one of the most enriched pathways after chaetocin treatment. We further revealed that chaetocin triggered the activation of Hippo pathway in ESCC cells, which is characterized by elevated phosphorylation levels of almost all core proteins in Hippo pathway, such as MST1 (Thr183), MST2 (Thr180), MOB1 (Thr35), LAST1 (Thr1079 and Ser909) and YAP (Ser127), ultimately leading to decreased nuclear translocation of YAP. Moreover, the MST1/2 inhibitor XMU-MP-1 not only partially rescued the inhibitory effect chaetocin-induced proliferation, but also rescued the chaetocin-induced apoptosis in ESCC cells. Furthermore, in vivo results confirmed the antitumor effect of chaetocin and its relationship with Hippo pathway. Taken together, our study demonstrates that chaetocin exhibits anticancer effects in ESCC via activation of Hippo pathway. These results provide an important basis for further research of chaetocin as a potential candidate for ESCC treatment.

Synthesis of two nitrogen-doped carbon quantum dots to construct fluorescence probes for sensitive Hg2+ detection with dual signal output

The rapid and sensitive detection of heavy metal ions is of great importance in food safety and for the environment. Therefore, two novel probes, M-CQDs and P-CQDs, based on carbon quantum dots were utilized to detect Hg²⁺ based on fluorescence resonance energy transfer and photoinduced electron transfer mechanisms. The M-CQDs were prepared from folic acid and m-phenylenediamine (mPDA) using a hydrothermal method. Similarly, the novel P-CQDs were obtained according to the same synthetic procedure used to create M-CQDs except the mPDA was replaced with p-phenylenediamine (pPDA). Upon the addition of Hg²⁺ to the M-CQDs probe, the fluorescence intensity reduced significantly with a linear concentration range between 5 and 200 nM. The limit of detection (LOD) was calculated to be 2.15 nM. On the contrary, the fluorescence intensity of the P-CQDs was enhanced greatly after the addition of Hg²⁺. The Hg²⁺ detection was realized with a wide linear range from 100 to 5000 nM and the LOD was calculated to be as low as 52.5 nM. The fluorescence "quenching" and "enhancing" effect exhibited by the M-CQDs and P-CQDs, respectively, is due to the different distribution of -NH₂ in the mPDA and pPDA precursors. Notably, paper-based chips modified with M/P-CQDs were established for visual Hg²⁺ sensing, demonstrating the possibility for real-time detection of Hg²⁺. Moreover, the practicality of this system was confirmed through the successful measurement of Hg²⁺ in tap water and river water samples.

A sensitive enzyme-free electrochemical sensor based on a rod-shaped bimetallic MOF anchored on graphene oxide nanosheets for determination of glucose in huangshui

In this work, we propose a bimetallic Ni-Co based MOF attached to graphene oxide (GO) by a one-step hydrothermal approach which may be employed as an electrochemical enzyme-free glucose sensor. Due to the obvious synergistic catalysis of Ni and Co, as well as the combination of NiCo-MOF and GO, NiCo-MOF/GO not only enhances energy transfer and electrocatalytic performance but also provides a larger surface area and more active sites. Electrochemical studies show that NiCo-MOF/GO exhibits outstanding electrochemical activity, with a sensitivity of 11 177 μA mM^-1 cm^-2 and 4492 μA mM^-1 cm^-2 in the linear ranges of 1-497 μM and 597-3997 μM, a detection limit of 0.23 μM, and a response time of 2 seconds. More importantly, the newly fabricated sensor is successfully applied for glucose determination in huangshui. This method provides a novel strategy for the controlled fermentation process and product quality of Chinese baijiu.

Discrimination of Chinese green tea according to tea polyphenols using fluorescence sensor array based on Tb (III) and Eu (III) doped Zr (IV) metal-organic frameworks

A facile and rapid fluorescence sensor array based on Tb (III) and Eu (III) doped Zr (IV) metal-organic frameworks was proposed for Chinese green tea discrimination. According to large porosity of Tb@UiO-66-(COOH)₂ and Eu@UiO-66-(COOH)₂, phenolic hydroxyl groups of tea polyphenols could coordinate with free carboxylic acid groups and was captured into the pores, which led to the disturbance of electronic structure of ligand and inhibited the energy transfer efficiency from ligand to Tb (III) and Eu (III) center, causing the fluorescence quenching effect. Based on Hierarchy Cluster Analysis and Linear Discrimination Analysis, the fluorescence sensor array was employed for successful tea polyphenols classification through the analysis of different fluorescence quenching effect to tea polyphenols. Green tea samples within different categories and grades were also successfully discriminated using this assay according to tea polyphenols, providing a new method for Chinese green tea identification.

The microsphere of sodium alginate-chitosan-Pichia kudriavzevii enhanced esterase activity to increase the content of esters in Baijiu solid-state fermentation

Pichia kudriavzevii was one of the important aroma-producing fungi in the solid-state fermentation of Baijiu, and immobilization was an effective strategy for improving microbial performance. Herein, P. kudriavzevii cells were immobilized in a gel network that crosslinked by chitosan and sodium alginate to form sodium alginate/chitosan-P. kudriavzevii microspheres (SA/CS-PMs). Their structural characteristics and formation processes were characterized by SEM and FT-IR. The effect of synthesis conditions on the performance of microspheres were determined by single-factor experiments. Under the optimal conditions, the SA/CS-PMs could increase the amylase activity of the fermentation broth by 57.18%, the esterase activity by 66.13%, the content of ester by 67.04%, and could be reused at least three times. Further research results indicated that the content of ester could be increased significantly in Baijiu solid-state fermentation with the SA/CS-PMs. In conclusion, the SA/CS-PMs could improve the ester production ability of P. kudriavzevii by increasing the esterase activity, which was a valuable exploration of directional biosynthesis and a feasible strategy to improve solid-state fermentation quality.

A sensitive electrochemical sensor based on 3D porous melamine-doped rGO/MXene composite aerogel for the detection of heavy metal ions in the environment

Herein, we developed a unique screen-printed carbon electrode (SPCE) with three-dimensional melamine-doped graphene oxide/MXene composite aerogel (3D MGMA) modification, which is used for the simultaneous and sensitive detection of three metal ions (Zn²⁺, Cd²⁺, and Pb²⁺) in the environment. A self-assembly method was used to fabricate 3D MXene aerogels based on MXene, graphene oxide (GO), and melamine. Notably, the network-like 3D structure combining 2D MXene and rGO sheets can provide a high ratio of surface area and enriched functional clusters, which are beneficial for improving the electrical conductivity and promoting the uptake of heavy metal ions. In the linear range of 3-900 μg L^-1, the constructed innovative sensing platform can sensitively detect Zn²⁺, Cd²⁺, and Pb²⁺ simultaneously, with detection limits of 0.48 μg L^-1,0.45 μg L^-1 and 0.29 μg L^-1 respectively. This work reflects precision and reliability in the detection of three water samples (tap water, Minzhu lake and Yangtze River) and four cereal samples (sorghum, rice, wheat and corn), proposing a novel strategy for monitoring heavy metal ions in the natural environment.

Microswimmer-Based Ultrasensitive Dual-Signal Ratiometric Electrochemical Homogeneous Aptasensor with Functionalized Co-UiO-66 for the Single-Step Detection of HER2 in Whole Blood

The ability to efficiently detect trace disease biomarkers in whole blood remains an enormous challenge. Researchers have paid more attention to the homogeneous electrochemical ratio biosensor due to its self-calibration capability and improved detection accuracy. However, proportional homogeneous electrochemical sensing is difficult to achieve and typically requires functional modification of the electrode or the preparation of complex materials. Herein, a dual-signal ratiometric aptamer homogeneous electrochemical microswimming detection device with active capture capability and one-step detection of human epidermal growth factor receptor-2 (HER2) is proposed. The homogeneous electrochemical biosensor is fabricated based on a functionalized nanocomposite double-stranded DNA({single-stranded DNA-ferrocene (Fc)-aptamer})@Co-UiO-66 with catalase properties and adsorptive properties to electroactive toluidine blue (TB) molecules. Encapsulation of Co-UiO-66 material with dsDNA (ssDNA-Fc-Apt) containing HER2 aptamer as a gate switch inhibited its ability to adsorb TB molecules. This functionalized Co-UiO-66 material can catalyze hydrogen peroxide. Using hydrogen peroxide as a fuel, it breaks down to release oxygen bubbles, creating a propulsion force that drives dsDNA(ssDNA-Fc-Apt)@Co-UiO-66 target HER2 through whole blood. When the surface dsDNA (ssDNA-Fc-Apt)@Co-UiO-66 recognizes HER2, a strand displacement reaction occurs, and the ssDNA-Fc is released into solution. The HER2 aptamer is coiled because it targets HER2, and the ability to adsorb TB molecules is restored due to the exposed surface of Co-UiO-66. A certain negative voltage is applied to the ITO electrode, and due to the electrostatic attraction, the TB molecules and ssDNA-Fc are adsorbed and enriched on the surface of the electrode by electrostatic attraction, which produces two strong and oppositely changing electrochemical signals, and the electrochemical signals depend on the HER2 concentration. It can sensitively detect HER2 biomarkers in only 40 min with the detection range of 0.0001-10 ng/mL and detection limits as low as 10 fg/mL. The electrochemical microswimmer for the detection of trace disease biomarkers involves a one-step process of capture, signal change, and detection.

An ultrasensitive electrochemical sensor based on antimonene simultaneously detect multiple heavy metal ions in food samples

Here, we constructed a novel ultra-sensitive electrochemical sensor based on ZIF-67@antimonene (AMNFs) nanocomposites which are based on the first-principles density functional theory the adsorption properties of antimonene on heavy metal ions were studied for simultaneous determination of Cu²⁺, Pb²⁺ and Hg²⁺. The ZIF-67@AMNFs was prepared by using ZIF-67 MOF surface loaded with a large amount of antimonene sheet. Its morphology and crystal structure were characterized by Transmission electron microscope (TEM), Energy Dispersive Spectroscopy (EDS), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Functional ZIF-67@AMNFs due to its unique layered structure, large active surface area, strong adsorption capacity and good electrical conductivity. In addition, the adsorption capacity of the sensor electrode for Cu²⁺, Pb²⁺ and Hg²⁺ was effectively enhanced. The detection limits of Cu²⁺, Pb²⁺ and Hg²⁺ were 0.01 pM, 0.042 pM and 0.031 pM, respectively. The determination mechanism of Cu²⁺, Pb²⁺ and Hg²⁺ was further clarified based on the adsorption properties and electrochemical accumulation of antimonene on metal atoms. It has been successfully applied to the simultaneous determination of Cu²⁺, Pb²⁺ and Hg²⁺ in rice, sorghum, corn, milk, honey and tea samples, and has good practicability.

Organic acid-induced triple fluorescent emission carbon quantum dots identification of distilled liquor

An acid-sensitive carbon dot fluorescence sensing array was investigated for the differentiated recognition of distilled spirits. Due to the electrostatic interactions between CDs and organic acids, organic acids affect the protonation and fluorescence properties of CDs, which in turn modify the CDs triple fluorescence emission. The regular linear variation of the fluorescence sensor was found under acidic conditions (3.0 < pH < 6.2). A comprehensive study of acids with selectivity, different concentrations (0.1 mM, 1 mM, 10 mM, 40 mM), different types (8 species) and mixed acids (formic acid and acetic acid), and good quantification capability for acetic acid (0.01-1 mM). Demonstrating good recognition ability of the sensor array for complex analyte. On this basis, the fluorescence sensor array was applied to the classification and recognition of liquors. LDA has realized the identification of 16 kinds of Baijiu and 21 kinds of distilled liquors with an accuracy of 100%.

A novel electrochemical biosensor based on AMNFs@ZIF-67 nano composite material for ultrasensitive detection of HER2

Antimonene (AMNFs) is a new kind of sp²-bonded honeycomb lattice two-dimensional material with strong rod-rail coupling, stability and hydrophilicity. Compared with graphene, antimonene has better sensitivity in DNA molecular sensing. We developed a suitable biosensor-Cd²⁺-aptamer@AMNFs@ZIF-67 nanocomposite for HER2 biomarker detection. Two-dimensional antimonene can be grown on the surface of ZIF-67 to enhance stability and biocompatibility. The aptamer chain can also be adsorbed on the surface of antimonene, and the complexes of the aptamer and the marker can be detached analytically after targeting the biomarker. The detection limit (LOD) was 4.853 fg/mL within 60 min, the detection range was 0-1000 pg/mL, and the LOD was lower than the existing HER2 aptamer biosensors. The results show that the biosensor has certain applicability and potential, and is expected to be a powerful tool for breast cancer diagnosis in the future.

Colorimetric detection of Cu2+ based on the inhibition strategy for etching reaction of AgNCs

In this study, an efficient and simple colorimetric method for sensing of Cu²⁺ was established using inhibition effect of Cu²⁺ to the etching reaction of silver nanocubes (AgNCs) induced by H₂O₂. The etching reaction of AgNCs changes its morphology and absorbance with the visual appearance from yellow to colorless. On the contrary, the presence of Cu²⁺ can significantly inhibit the etching progress. Thus Cu²⁺ induces the obvious absorbance enhancement compared with AgNCs/H₂O₂ system. This design realizes colorimetric detection of Cu²⁺ based on the inhibition effect of etching reaction using AgNCs nanoprobe. The colorimetric response of AgNCs nanoprobe in ΔAbs_417.5 shows the linearity with the increasing concentrations of Cu²⁺ from 0.01 to 40 μM with good selectivity. The concentration limit of Cu²⁺ efficaciously discriminated by the naked eye is as low as 0.01 μM. Furthermore, the Euclidean distance (ED) of the difference map in RGB change before and after response with Cu²⁺ is applied for further visualization recognition of Cu²⁺. All the above results indicate the outstanding practicability and accuracy of the proposed assay for Cu²⁺ sensing.

Electrochemical detection of the p53 gene using exponential amplification reaction (EXPAR) and CRISPR/Cas12a reactions

An improved electrochemical sensor has been developed for sensitive detection of the p53 gene based on exponential amplification reaction (EXPAR) and CRISPR/Cas12a. Restriction endonuclease BstNI is introduced to specifically identify and cleave the p53 gene, generating primers to trigger the EXPAR cascade amplification. A large number of amplified products are then obtained to enable the lateral cleavage activity of CRISPR/Cas12a. For electrochemical detection, the amplified product activates Cas12a to digest the designed block probe, which allows the signal probe to be captured by the reduced graphene oxide-modified electrode (GCE/RGO), resulting in an enhanced electrochemical signal. Notably, the signal probe is labeled with large amounts of methylene blue (MB). Compared with traditional endpoint decoration, the special signal probe effectively amplifies the electrochemical signals by a factor of about 15. Experimental results show that the electrochemical sensor exhibits wide ranges from 500 aM to 10 pM and 10 pM to 1 nM, as well as a relatively low limit detection of 0.39 fM, which is about an order of magnitude lower than that of fluorescence detection. Moreover, the proposed sensor shows reliable application capability in real human serum, indicating that this work has great prospects for the construction of a CRISPR-based ultra-sensitive detection platform.

Typing of cancer cells by microswimmer based on Co-Fe-MOF for one-step simultaneously detect multiple biomarkers

Capturing, identifying, and counting CTCs cancer cells that have escaped from the tumor and wandered into the bloodstream is a major challenge. We proposed a noval microswimmer dual-mode aptamer (electrochemical and fluorescent)-(Mapt-EF) homogeneous sensor with active capture/controlled release double signaling molecule/separation and release cell based on the Co-Fe-MOF nanomaterial for simultaneous one-step detection of multiple biomarkers protein tyrosine kinase-7 (PTK7), Epithelial cell adhesion molecule (EpCAM), and mucin-1 (MUC1) for diagnosis of multiple cancer cell types. The Co-Fe-MOF is a nano-enzyme capable of catalyzing the decomposition of hydrogen peroxide to release bubbles of oxygen, producing a driving force to conduct hydrogen peroxide through the liquid, and has the capacity to self-decompose during the catalytic process. Phosphoric acid is present in the aptamer chains of PTK7, EpCAM, and MUC1, and the aptamer chains are adsorbed to the surface of the Mapt-EF homogeneous sensor in the form of a gated switch to inhibit the catalytic decomposition activity of hydrogen peroxide. The Mapt-EF homogeneous sensor has the capability to actively target biomarkers that can be entrained by oxygen bubbles without being degraded. The detection time of the sensor was 20 min, the detection limits were 9.6 fg/mL, 8.4 fg/mL and 7.7 fg/mL with the linear range was 0-20 pg/mL, respectively. The Mapt-EF homogeneous sensor has high detection sensitivity, and its detection limit can reach the level of single cell at the lowest. The Mapt-EF homogeneous sensor has great application potential in clinical detection and analysis of tumor cells.