Lower Limit Research Articles

Observational constraints on asymptotic safety inflation in gravity’s rainbow

Using suitable Renormalization Group (RG) based re-summation of quantum corrections to R2 term, a re-summed version of the effective Lagrangian can be obtained (Demmel et al.,2015). In the context of gravity as an Asymptotically Safe (AS) theory, authors of Refs. Liu et al. (2018), Koshelev et al. (2023) proposed a refined Starobinsky model, LAS=Mp2R/2+(α/2)R2/[1+βln(R/μ2)], where R is the Ricci scalar, α and β are constants and μ is an energy scale. In the present work, we embed this underlying effective Lagrangian within the framework of gravity’s rainbow. By implementing the COBE normalization and the Planck constraint on the scalar spectrum, we demonstrate that the power spectrum of curvature perturbation relies on α and β, as well as on a rainbow parameter. Similarly, the scalar spectral index ns is influenced by β and the rainbow parameter, yet remains unaffected by α. Additionally, the tensor-to-scalar ratio r solely depends on the rainbow parameter. Remarkably, when requiring ns to be consistent with the Planck collaboration at 1σ confidence level, the upper limit on the tensor-to-scalar ratio r<0.036 can be naturally satisfied. This value potentially holds promise for potential measurement by Stage IV CMB ground experiments and is certainly within reach of future dedicated space missions.

Construction of high strength PVA/cellulose conductive hydrogels based on sodium citrate/aluminium chloride dual ions regulation

Hydrogels used for flexible sensing usually require a good balance between mechanical strength and conductivity. In this study, polyvinyl alcohol/carboxymethyl cellulose/cellulose nanofibers (PVA/CMC/CNF) hydrogels with multi-hierarchical structures were firstly prepared by adjusting the CNF content. Then, PVA/CMC/CNF-xM with excellent mechanical properties and conductivity were prepared by cyclic freezing-thawing and sodium citrate/aluminium chloride (Na3Cit/AlCl3) dual ions salt equilibrium methods. Results showed that at an ion concentration of 3 mol/L, PVA/CMC/CNF-3 M hydrogel exhibited a tensile strength, elongation at break and conductivity of 3.41 MPa, 1271 % and 0.35 S/m, respectively. The structural evolution of PVA/CMC/CNF-xM conductive hydrogels were studied, and the results indicated that Cit3− formed numerous intermolecular hydrogen bonds, while Al3+ could strongly coordinate with carboxyl and hydroxyl groups between the polysaccharide chains. Meanwhile, PVA/CMC/CNF-3 M possessed a low strain detection limit of 1 %, making it not only can be used for human motion monitoring, but also information encoding and transmission. This work may provide a facile approach for preparing high-strength and conductive hydrogels, which can be applied in flexible wearable electronic devices and information transmission.

“All-on-a-Tube” POCT of Salmonella in large-volume sample

Point-of-care testing (POCT) of pathogenic bacteria at low concentrations is vital to early warning of bacterial contaminations. A disposable centrifuge tube was reconstructed in this study for sensitive Salmonella detection in large-volume samples, where the entire bacterial detection progress from separation to detection, was performed within the tube. The bottom of this centrifuge tube was assembled with a flexible stirrer containing a pair of circular magnets, which was rapidly rotated using a DC motor to produce the vortex for simultaneous mixing and capture of target bacteria. Besides, immune manganese dioxide nanoflowers were synthesized and used to label target bacteria, followed by mimicking catalyze colorless TMB substrate into blue TMBox product. The product image was captured and analyzed by a smartphone App to quantitatively determine the target bacteria. This POCT centrifuge tube effectively achieved a separation efficiency of approximately 80 % for target bacteria from a 10 mL sample, enabling the detection of target bacteria within the range of 1.3 × 101 to 1.3 × 104 CFU/mL in 1 h, with a low detection limit of 13 CFU/mL. More importantly, this reconstructed centrifuge tube demonstrated its potential as a laboratory consumable for bacterial detection in routine screening owing to the features of low cost, easy operation and high integration.

Novel sensing signal mode constructed by dual responsive silence layer combined with catalytic hydrogen evolution

For electrochemical assays, to obtain sensing signals, the redox of the modified electrochemical signal substance to provide a detectable signal is commonly required. However, during the process of assembly and sensing, the loss of signal substance caused by multiple steps of modification, incubation, and washing would lead to non-negligible fluctuation of signal and lack of reproducibility. To overcome this issue, a novel sensing signal mode without electrochemical signal substance was developed. By introducing electrochemical catalytic hydrogen evolution into the sensing scheme, and taking the overpotential as the detectable signal, the sensing system was constructed in the absence of electrochemical signal substance. As a proof of concept, the sensor was used to quantify squamous cell carcinoma antigen, a model analyte, and exhibited an excellent analytical performance with a wide linear range from 0.100 ng mL−1 to 100 ng mL−1 and a low detection limit of 52.4 fg mL−1. As envisioned, the sensor exhibited excellent long-term stability and reproducibility due to the avoidance of signal substance. This method provided a new way for the design of electrochemical sensors.

Synthesis and characterization of a copper-based metal–organic framework and its application in microextraction and determination of chlorpyrifos by ion mobility spectrometry

This study describes an innovative method for the microextraction and determination of chlorpyrifos, utilizing a newly synthesized copper-based metal–organic framework (MOF) with 3,3ʹ-thiodipropionic acid as the ligand. This approach offers a sensitive and reliable solution for the ultra-trace determination of chlorpyrifos in various matrices, highlighting its potential for broader environmental and food safety applications. To minimize environmental impact, a hydrothermal method was chosen for MOF synthesis. The MOF was fully characterized using FT-IR, X-ray diffraction, FESEM-EDX, BET, zeta potential analysis, and XPS; and integrated into a dispersive solid-phase microextraction (DSPME) technique, paired with ion mobility spectrometry (IMS) for chlorpyrifos detection. The DSPME procedure has been optimized for extraction efficiency, minimal solvent use, and low absorbent consumption. A low detection limit of 0.65 ng mL−1 was observed and validated along with a linear detection range of 1.0–400.0 ng mL−1 as the result of this optimization. Experiments with water, pear fruit, and soil samples demonstrated the method’s practicality and superior performance compared to existing techniques, showcasing its potential for real-world applications.

Micro-biosensor fabrication by microfluidic channel for simultaneous detection of choline and creatine

Choline, and creatine are two common metabolites in the nervous system, and dysregulation in choline and creatine levels is associated with the development and recurrence of glioma. In this paper, we developed an enzymatic micro-biosensor for real-time combined sensing of choline and creatine. We simulated the influence of enzyme layer thickness and electrode spacing on the electrode work with COMSOL software, then employed microfluidic channels to immobilize an enzyme layer with a precise extent. And the sensor worked with this technique to transfer and pattern choline oxidase (ChOx) and the mixture of creatinase (Cr) and sarcosine oxidase (SO) onto targeted sites on microelectrode arrays (MEA). The combined sensing micro-biosensor was confirmed that it has high sensitivity for choline and creatine with 208 and 35 μA mM−1 cm−2, respectively, and also low detection limits to around 1 and 10 μM, respectively, with relative rapid response times within 10 s (≤10 s). This work demonstrates that microfluidic channels can be an efficient method for fabricating multi-analyte enzymatic micro-biosensor.

Customized flexible iontronic pressure sensors: Multilevel microstructures by 3D-Printing for enhanced sensitivity and broad pressure range

Flexible capacitive pressure sensors stand out for their energy efficiency, rapid responsiveness, and exceptional durability, with their performance hinging on the intricate design of microstructures and the strategic selection of dielectric materials. However, creating cost-effective and practical fabrication methods for these components continues to pose a significant challenge. This study unveils an innovative iontronic flexible pressure sensor that integrates an ionic layer with sophisticated multilayer microstructures, setting new benchmarks in pressure sensing technology. The sensor operates within an expansive pressure range, achieving sensitivities as high as 92.14 kPa−1 at pressures from 0 to 50 kPa, and 22.96 kPa−1 at pressures ranging from 50 to 800 kPa, demonstrating extraordinary sensitivity. It also achieves an exceptionally low detection limit of 6.67 Pa and features swift response times of 56 ms to activate and 18 ms to deactivate. Enhanced by the addition of CuSO4, the sensor not only withstands freezing conditions but also significantly boosts sensitivity. Moreover, this sensor is capable of detecting human joint movements and subtle pressure fluctuations under high-pressure conditions, suggesting a breakthrough in the field. This research presents a simple, reliable, and cost-efficient method for developing flexible iontronic pressure sensors, poised to revolutionize applications in wide-ranging pressures and adverse temperature environments.

Copper@MXene quantum dots-aerogel: High-performance peroxidase mimic for direct pirimiphos-methyl pesticide detection

Due to their cost-efficiency and heightened sensitivity, the rational design of artificial nanozymes has become a paramount research direction. In this investigation, we elaborate on a simplified freeze-drying methodology for fabricating Cu@MXene quantum dots-aerogel (Cu@MQDs-aerogel), which possesses augmented peroxidase-mimicking activity. Through steady-state fluorometric analysis, we delve into the catalytic mechanism of Cu@MQDs-aerogel, uncovering its proficiency in decomposing H2O2 into reactive hydroxyl radicals (OH). Density functional theory (DFT) calculations further validate that the outstanding catalytic prowess of Cu@MQDs-aerogel stems from the interfacial Cu-Ti dimer active sites, significantly activating adsorbed H2O2 and facilitating its decomposition into OH. As a result, we introduce a sensitive colorimetric sensor for pirimiphos-methyl detection, achieving a low detection limit of 0.65 nM. Additionally, it exhibits a narrow relative standard deviation (RSD) interval spanning from 1.03 % to 2.66 %. This study introduces a novel strategy for the design and synthesis of MQDs-based peroxidase-like enzymes, highlighting their significant potential in environmental pollutant detection.

Preparation and evaluation of Puerarin-loaded PLGA nanoparticles for improving oral bioavailability in SD rats

BackgroundPuerarin (Pue) is an isoflavone compound with significant therapeutic effect on cardiovascular diseases, but its poor water solubility and low oral bioavailability limit clinical application. MethodsIn this study, Pue was prepared into PLGA nanoparticles (Pue-PLGA NPs) by emulsion solvent volatilization method. The morphology, particle size, Zeta potential, X-ray diffraction (XRD), and fourier transform infrared (FTIR) of the NPs were characterized. Additionally, their stability and in vitro release were evaluated. SD rats were orally administered wtih Pue and Pue-PLGA NPs, and a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established to determine the concentration of blood samples and to investigate the pharmacokinetic behaviour of Pue and Pue-PLGA NPs in rats. ResultsThe NPs were observed by transmission electron microscopy (TEM) as regular spheroids and uniformly dispersed. The average particle size of the NPs was (167.1±5.26）nm, the Zeta potential was (-29.88±2.46)mV, the encapsulation rate was (83.12 %±4.73 %) and the drug loading capacity was (7.75 %±1.81 %). The results of in vitro release showed that the drug was released slowly and continuously from the NPs, reaching the release platform in 24 h, and the cumulative release amount was (88.55±2.86) %. The pharmacokinetic results showed that the AUC0–24, AUC0-∞, Cmax, Tmax, t1/2, MRT0–24 and MRT0-∞ of Pue-PLGA NPs were 2.196, 1.978, 1.327, 1.5, 1.385, 3.915 and 3.140 times of Pue, respectively. The relative bioavailability was (197.82±25.28) %. ConclusionThese results indicated that the prepared nanoparticles had small particle size, high encapsulation rate, drug loading capacity and good slow-release effect, and could significantly improve the oral bioavailability of Pue in rats.

Preparation, characterization, and ex vivo evaluation of isoxanthohumol nanosuspension

This study assessed the equilibrium solubility, oil–water distribution coefficient, and dissociation constant of Isoxanthohumol (IXN), and formulated IXN nanoparticles (IXN-Nps) using a micro media grinding method. The research characterized the particle size, polydispersity index, zeta potential, morphology, and structure of the nanoparticles, and evaluated the optimal cryoprotectant. Additionally, the study examined the toxicity and in vitro and in vivo release of IXN on HT-29 cells. IXN is classified as a Biopharmaceutical Classification System (BCS) II class drug with weak acidity. The average particle size of IXN-Nps is 249.500 nm, with a polydispersity index (PDI) of 0.149 and a zeta potential of −25.210 mV. The research identified 5 % mannitol as the optimal cryoprotectant. Compared to IXN, the half-maximal inhibitory concentration of IXN-Nps decreased to one-third, demonstrating a significant inhibitory effect on HT-29 colon cancer cells. The in vitro cumulative release rate of IXN-Nps within 24 h was 3.5 times higher than that of the IXN solution. In vivo pharmacokinetic results revealed that the oral bioavailability of IXN-Nps increased significantly by 2.8 times compared to the IXN solution. The correlation coefficient (r = 0.9227) exceeded the critical value for significance at the 0.01 (r = 0.834) level, indicating a strong correlation between in vivo and in vitro results. Consequently, the nanosuspension overcame the low solubility limitation of IXN and proved to be an effective method for enhancing the oral bioavailability of IXN

Simple and low-cost thrombin activity assay using screen-printed electrodes with portable electrochemiluminescence device

Real-time monitoring of thrombin activity is essential for preventing, diagnosing, and treating coagulation-related diseases. Herein, we present a simple, disposable electrochemiluminescence (ECL) biosensor for thrombin activity assay based on screen-printed electrodes (SPE). The thrombin-specific peptide substrate Mpr (4-Methoxybenzyl group)-GGRK-Fc (ferrocene) was identified from four candidates using molecular docking and specificity constant experiments. Mpr-GGRK-Fc exhibited the highest apparent specificity constant (kcat/KM) of 2.09 × 1012 M−1 s−1, indicating superior affinity and specificity for thrombin. Thrombin catalyzes the cleavage of Mpr-GGRK-Fc, resulting in the detachment of Fc from the electrode surface, which leads to an increase in ECL intensity. Under optimal conditions, the biosensor exhibits a wide linear range from 1.0 × 10−4 U/mL to 1.0 U/mL, with a low detection limit of 4.02 × 10−5 U/mL. The biosensor shows high specificity for thrombin among a range of proteins. Compared to commercial fluorescence kits, our biosensor offers superior sensitivity, selectivity, and stability in detecting thrombin activity in whole blood, making it a promising tool for bedside clinical applications.

Self-assembly Pt hollow nanospheres for highly selective and ultrasensitive detection of dopamine

Abnormal concentration of dopamine, one critical neurotransmitter in central nervous system, causes several neurological diseases associated with behavioral responses and brain functions in human beings. Highly sensitive detection of dopamine is of great significance yet challengeable. In this work, Pt hollow nanospheres (Pt HNSs) with a uniform diameter of 30 nm were successfully synthesized in water by self-assembly method under room temperature. The fabricated Pt hollow/Nafion nanospheres modified glassy carbon electrode (Pt HNSS/Nafion/GCE) exhibited superior electrocatalytic performance, with peak currents 2.24 and 4.54 times higher than those of Nafion-modified glassy carbon electrode (Nafion/GCE) and bare glassy carbon electrode (GCE), respectively. Theoretical calculations indicate that dopamine has an adsorption energy of −3.18 eV on the Pt(111) surface, with an electron transfer of + 1.84 |e|, aligning with the 2-electron transfer mechanism. Furthermore, the low energy barrier observed during dopamine oxidation process suggests that the Pt(111) surface is highly favorable for dopamine oxidation. Meanwhile, Pt HNSS/Nafion/GCE electrochemical sensor exhibits highly sensitive and selective response in determination of dopamine ranging from 0.01 to 250 μM with low detection limits of 0.804 nM (S/N = 3). Moreover, the electrochemical sensor shows reliable signals in real test with great anti-interference and stability during the experiments, making it a promising candidate for applications in dopamine sensing.

Evaluation of shear strength models for ETS-FRP-retrofitted beams subjected to shear-critical failure

This study presents a new shear strength model for reinforced concrete beams strengthened with embedded through-section fiber-reinforced polymer (ETS-FRP) bars, accounting for three potential failure modes: shear compression, shear tension, and shear-balanced failures. The bonding-based analysis for ETS-FRP retrofitting elements is integrated into the developed shear approach. Validation against available test data reveals that the developed model outperforms existing methods in predicting the shear capacity of ETS-FRP-intervened beams. The developed computation technique also demonstrates consistent accuracy across a broad range of design variables and adheres to all upper shear limits in the design codes. To serve practical use, this study provides specific design strategies and perspectives for optimizing ETS-FRP strengthening systems and determining appropriate shear reinforcement amounts for ETS-retrofitted beams.

Pseudo-dynamic stability analysis of 3D rock slopes considering tensile strength-modified Hoek–Brown failure criterion: Seismic UBLA implementations

The Hoek-Brown (HB) criterion has found extensive application in the stability analysis of intact or jointed rock slopes, in both two-dimensional (2D) and three-dimensional (3D) contexts. In the early days, the assessment of Hoek-Brown slopes rarely incorporated tensile strength until, recently, limited studies examined the tension-controlled toppling failure at the sliding head. Nevertheless, the adapted tensile strength, which is extrapolated from the HB envelope the tensile regime, has been found overestimate experimental results. Thus, for more realistically representing the influence of rock tensile strength, the present study introduces a novel procedure for assessing the seismic stability of 3D HB slopes. In this study, the tensile strength-modified HB envelopes considering cut-off effects are derived in the principal stress space and Mohr space. To assess the slope stability, the obtained HB envelope is employed in a multi-cone mechanism based on upper bound limit analysis (UBLA). Specifically, the counter of this mechanism is determined by 10 optimized dependent rupture angles, highly considering the nonlinearity of the Hoek-Brown envelope compared to the traditional linearization strategies. As an improved seismic stability analysis, the seismic load is characterized by a modified pseudo-dynamic method. Analytical expressions for two stability indicators, i.e., the stability number and safety factor, are derived. Comparisons with numerical simulations demonstrate the rationality of the proposed procedure. Parametric analysis indicates the significant effect of the tension cut-off on the HB rock slope stability and the contour of the sliding surface.

Eu(III) encapsulation strategy to construct intelligent ratiometric luminescent sensor for efficient detection of phenylglyoxylic acid biomarker in bodily fluids

Herein, a desirable MOF-based luminescent sensor of Eu3+@ZnMOF is fabricated through post-synthesis strategy. Based on response differences of the inherent monitoring signal at 442 nm and the secondary monitoring signal at 699 nm introduced by encapsulating Eu3+ ions, the prepared Eu3+@ZnMOF displays great superior as a ratiomertic luminescent sensor with high sensitive and selective, rapid response time (less than 1 min), superior detection limit (3.89 ng·mL−1), and favorable recyclable performance (at least 6 cycles) in detecting phenylglyoxylic acid (PGA) biomarker over other urine and serum species. Furthermore, Eu3+@ZnMOF also demonstrates exceptional detectability and remarkable reliability in tracing PGA levels within actual serum and urine samples. On the basis of PGA levels controlled luminescence changes of Eu3+@ZnMOF under UV light, an intelligent detection platform is developed by integrating tandem combinational “AND” logic gates to achieve more convenient and intuitive detection of PGA levels in body fluids. Besides, photoinduced electron transfer and internal filtering effect are demonstrated to be responsible for the luminescence sensing. This work not only offers a validated strategy for the design of MOFs-based ratiometric luminescent sensors, but also presents an approach in efficient, rapid, and intelligent detection of biomarkers in body fluids.

Fast and in-situ electrodeposition of MXene/AuNPs composite for multiplexed and sensitive detection of infectious biomarkers using an electrochemical biosensor

Rapid, accurate, and cost-effective strategies for the multiplexed and quantitative detection of multiple infectious disease biomarkers are still lack in hospital. Here, we introduce a multiplexed screen-printed electrode for the simultaneous detection of three infectious disease biomarkers: HBsAg, anti-HIV, and anti-TP. The electrode modified with in-situ deposition of gold nanoparticles (AuNPs) and MXene multilayered nanosheets. Comprehensive characterization confirms the morphology and electrochemical response of the AuNPs&MXene modified screen-printed electrode (AuNPs&MXene-SPE). AuNPs&MXene composite contributes to enhance sensitivity by maximizing surface area and improving electron transfer efficiency. The AuNPs&MXene-SPE exhibits outstanding detection performance for HBsAg, anti-HIV, and anti-TP. The AuNPs&MXene-SPE sensors achieve broad detection ranges (0.05–1000 ng/mL for HBsAg, 0.35–140 ng/mL for anti-HIV, and 0.25–100 ng/mL for anti-TP) accompanied by low limits of detection (0.01, 0.11, and 0.10 ng/mL, respectively). Applied to standard serum samples, the sensors showcase precision with relative standard deviations consistently below 5.0 %, affirming their suitability for complex solution environments. These sensors offer notable advantages, including cost-effectiveness, rapid response, high sensitivity, and specificity, eliminating the necessity for expensive equipment, which open avenues for the realization of point-of-care testing (POCT).

Dual signal Amplification-Mediated Aptamer-Based electrochemical biosensor for sensitive detection of exosomes

Exosomes, a class of extracellular vesicles carrying the biological information of their parent cells, have emerged as one of the most promising biomarkers for the early screening and prognostic monitoring of cancer. However, the effective capture and sensitive detection of cancer cell-derived exosomes pose significant challenges due to the inevitable interference from internal environment and the limited exosome abundance in clinical samples. Herein, we proposed an aptamer-based electrochemical biosensor combining with Au nanoprobe-mediated dual signal amplification for sensitive detection of tumor-related exosomes. Benefiting from the specific recognition of CD63 aptamer (CD63 Apt), the target exosomes were efficiently captured on the gold electrode, followed by trapping the iDNA-modified Au nanoprobe, which could induce the generation of hybridization chain reaction (HCR). The long double-stranded DNA produced by HCR procedure provided numerous insertion sites to RuHex, achieving the high sensitivity for exosome detection. Under the optimal experimental conditions, this aptamer-based electrochemical biosensor for MCF-7 cancer cell-derived exosome detection exhibited a good linear range within 5 orders of magnitude (from 1.29 × 104 to 1.29 × 108 particle/mL) with a low limit of detection (LOD) to 1.65 × 103 particle/mL. Furthermore, this biosensor possessed good stability and anti-interference ability. Therefore, this analysis platform is considered as a promising candidate for the exosome-based diagnosis and prognosis of cancer in clinical applications.

A FRET probe based on flavonol-benzothiazole for the detection of viscosity and SO2 derivatives

Sulfur dioxide (SO2) and viscosity play important roles in living organisms, and abnormal levels of them are associated with many diseases. Hence, a bifunctional fluorescence probe (E)-3-(2-(4-(4-(4-(6-fluoro-3-hydroxy-4-oxo-4H-chromen-2-yl)benzoyl)piperazin-1-yl)styryl)benzo-[d]thiazol-3-ium-3-yl)propane-1-sulfonate (HFBT) with fluorescence resonance energy transfer (FRET) properties was successfully constructed by using 3-hydroxyflavonol as the energy donor and benzothiazole sulphonate derivatives as the energy acceptor, and it can be used for the detection of SO2 derivatives (HSO3−/HSO32−) and viscosity. HFBT exhibits a large Stokes shift (245 nm), high resonance energy transfer efficiency (95.56 %), and excellent selectivity, anti-interference and low limit of detection (LOD = 0.057 μM) for HSO3−. The fluorescence intensity of HFBT at 608 nm gradually increases with the increase of viscosity. Interestingly, a visual HSO3− detection platform was successfully constructed and applied to the quantitative detection of HSO3− in food. Additionally, HFBT was successfully applied to imaging endogenous and exogenous HSO3− in cells. The successful development of HFBT provides an effective tool for the detection and imaging of HSO3− in food and cells.

Defective porous urchin-like ZnO/NiO microspheres-coated solid-phase microextraction fiber for analysis of trace polychlorinated biphenyls in milk.

Owing to the high lipophilicity of polychlorinated biphenyls (PCB), they easily accumulate in dairy products. Although usually present at very low levels, they pose a serious threat to human health. Therefore, developing a sensitive and reliable method for detecting PCB in dairy products is crucial. Herein, Herein, a metal-organic framework (MOF) material named with bimetallic nodes and double ligands was prepared as a precursor using a one-pot hydrothermal method. Defective porous urchin-like ZnO/NiO, derived from these MOF-based precursors (ZnNi-MOF-NH2) as a sacrificial template, was synthesized via pyrolysis to remove heat-sensitive ligands. To the best of our knowledge, this urchin-like nanostructured ZnO/NiO hybrid was utilized as a solid-phase microextraction (SPME) coating for the first time. Headspace SPME (HS-SPME) was developed for non-contact extraction of PCB in milk prior to gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. Under optimal conditions, the HS-SPME-GC-MS/MS method exhibited a wide linear range (0.01-1000ng·L-1), low limits of detection (0.003-0.025ng·L-1), and high enrichment factors (5714-9906). Additionally, the performance of the ZnO/NiO SPME fiber coating showed no noticeable decrease after 175 uses. The method was applied to trace PCB analysis in milk samples, yielding recoveries of 70.3-114.1%. The ZnO/NiO derived from MOF-based material provides a promising candidate for SPME coatings to extract PCB and other analogs.

Synthesis and nanoparticle formation of pyrazine, benzodithiophene (BDT) and fluorene containing conjugated polymer (P-PBF) and its biosensing performance toward catechol

The development of laccase-based biosensors, in particular, have attracted much interest due to their ability to detect highly toxic molecules in the environment. This article reports a novel biosensor for catechol detection that can be used to determine toxic molecules in the environment. For this purpose, a novel conjugated polymer (P-PBF) and conjugated polymer nanoparticles (P-PBFNPs) were synthesized and characterized, respectively. To our knowledge, research has yet to be done on conjugated polymer nanoparticle-based electrochemical biosensing platforms for catechol determination. The biosensor comprises a GE/P-PBF NPs/Lac electrode, constructed with P-PBF NPs deposited onto a bare graphite electrode followed by laccase (Lac) enzyme immobilization. While electrochemical characterization was performed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), surface characterization was performed by field emission scanning electron microscopy (FE-SEM). The biosensor exhibited high sensitivity (1.229 μA/μM.cm2), a good linear range (0.5–25 μM) and a low limit of detection (LOD) (0.49 μM). Moreover, the developed biosensor exhibited high selectivity in the presence of interfering analytes without any memory effects. The potential of the GE/P-PBF NPs/Lac electrode in tap water, green tea, synthetic urine and serum samples indicates the inspiring biosensing applications for monitoring environmental pollution.