Dopamine (DA), as one of the central neurotransmitters, plays an important role in many physiological and pathological processes. Detection of DA is critical to diagnose and monitor some neurological ...diseases. In this work, a novel on-off ratiometric electrochemical sensor with molecularly imprinted polymers (MIPs) as target molecule recognizer has been developed for selective and accurate detection of DA. Nanoporous gold (NPG) was electrodeposited on bare gold electrode, which not only benefited the output signal amplification, but also provided enlarged surface for immobilization of polythionine (pThi) and MIPs. Oxidation of DA and pThi served as response signal and internal reference signal, respectively. The oxidation peak currents of DA at +0.12 V increased with increasing the concentration of DA, while the peak currents of pThi at −0.2 V decreased simultaneously. Due to the specificity from MIPs and the built-in correction from pThi, the fabricated sensor showed excellent performance in view of selectivity and reproducibility. It's worth to mention that even if the surface area and morphology of working electrode underwent huge variation deliberately, the assay deviation among these ratiometric sensors was largely reduced around 10 times. The proposed sensor demonstrated a broad dynamic range of 0.3–100 μM, as well as a low detection limit of 0.1 μM (S/N = 3). Moreover, superior anti-interfering ability toward DA detection was obtained despite the presence of interferents at high concentration in artificial cerebrospinal fluid (aCSF). Therefore, this work is expected to provide an alternative pathway for constructing ratiometric electrochemical sensor and offer reliable determination of small molecules with high selectivity and stability.
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•A ratiometric electrochemical dopamine sensor was designed to improve the reproducibility and robustness.•Molecularly imprinted polymer was served as dopamine molecule recognizer with enhanced specificity.•Measurement error was controlled effectively even though sensors with diverse areas and morphologies were adopted.•The sensors showed excellent DA sensing performance in artificial cerebrospinal fluid (aCSF).
Continuous and real‐time sensoring has received much attention in biomarker monitoring, toxicity assessment, and therapeutic agent tracking. However, its on‐site application is seriously limited by ...several stubborn defects including liability to fouling, signal drifting, short service life, poor repeatability, etc. Additionally, most current methods require extra sample pretreatment, delaying timely acquisition of testing results. To address these issues, MXene‐Ti3C2Tx based screen‐printed electrode incorporated with a dialysis microfluidic chip is constructed for a direct and continuous multicomponent analysis of whole blood. Dual‐function of MXene is developed and allows for simultaneous quantification of different target compounds through one device. Importantly, ratiometric sensing tactic is easily implemented in the system, which greatly alleviates signal drifting. As a proof of concept, this novel sensor is applied in hemodialysis, and continuous assay of urea, uric acid, and creatinine levels in human blood is realized. This work paves a new path for 2D MXene in biomedical and sensing applications.
Introduction of MXene nanosheets into microfluidic chips contributes significantly to stable and sensitive signal outputs. Particularly, MXene acts as both a carrier and electrocatalyst, providing sufficient sites for locating other agents, and rendering occurrence of electrochemical reactions. Such dual‐function, together with the elaborately designed testing chip platform and strategies, realizes simultaneous quantification of different target compounds through one device.
2D materials are gaining great attention owing to their superior electrical, optical, and mechanical characteristics. In recent decades, 2D materials have demonstrated significant potential for the ...identification of disease‐related biomarkers based on semiconductor gas sensors. Herein, the recent progress of semiconductor gas sensors fabricated by 2D materials covering graphene, black phosphorus, transition metal dichalcogenides, MXenes, metal‐organic frameworks, metal oxide nanosheets, etc. is clearly described. First, the basic attributes of 2D materials are described, and their gas‐sensing mechanisms are also summarized. Second, the ability of 2D material‐based sensors in the detection of disease‐related gas molecules is also highlighted. Finally, some effective methods for enhancing the gas‐sensing performance of 2D materials are discussed, and the opportunities and challenges accompanying are also presented. This work could provide new avenues for material synthesis, sensor development, medical diagnosis, and the related fields.
Herein, the recent progress of semiconductor gas sensors based on 2D materials, including graphene, black phosphorus, transition metal dichalcogenides, MXenes, metal‐organic frameworks, and metal oxide nanosheets, etc., is clearly introduced. In addition, the mechanism and the potential of 2D‐material‐based gas sensors in disease diagnosis are fully discussed.
Rapid yet accurate detection of disease-related biomarkers is key for point of care testing, where there is an increasing demand for multi-index analysis. Here, we present a versatile device for ...multianalyte quantification based on the microfluidic technique and electrochemical sensor array. The analytes were shunted through inner-built channels to screen-printed electrodes installed at different positions of the chip. These electrodes were modified with different nanomaterials and sensing agents to afford specific responses to the corresponding indicators. To prove the applicability of the platform for multifunction, we chose leukemia as the model disease and determined four relevant markers: methotrexate (MTX), lactate dehydrogenase (LDH), uric acid (UA), and urea. They are indicative as/for the therapeutic drug (MTX), prognosis (LDH), and side effect (UA and urea). The sensing chip exhibited low detection limits of 35 nM, 25 U/L, 450 nM, and 20 μM toward the four analytes, which are much lower than their minimum contents in human serum. Furthermore, practical application of the chip was demonstrated by simultaneous detection of the four analytes in the blood plasma of rabbit. By simply replacing the modification agents, the sensing platform is expected to serve the detection of a wide range of chem/biosubstances in various fields.
Deep geological repository is usually constructed in a typical crystalline rock, granite. Therefore, comprehensive understanding on the thermo-mechanical properties of granite exposed to high ...temperature is crucial to repository design and risk assessment. Granite experiences a transition from strengthening to weakening as temperature increases; however, the critical temperature at which this transition occurs is still poorly known. Here we examined the physical and mechanical variations of granite specimens of three different grain grades. The specimens sourced from the same origin are heated up to 800 °C. Grain size distribution, thermal-induced cracks, and crack evolution under uniaxial compression of the heated specimens were examined by XRF (X-ray fluorescence spectrometric analysis, with a scanning capacity of 50 mm at a spatial resolution of 20 μm), SEM (Scanning electron microscope) and AE (Acoustic emission), respectively. We found that grain size heterogeneity quantified by the coefficient of variation (CV) modulates the critical temperature magnitude, and the granite specimen with a higher CV exhibits a lower critical temperature. The cracks reducing the granite strength are induced by grain mismatch due to inconsistent thermal expansion. Nonuniform distribution of grain size enhances the mismatch and broadens the favorable path for crack propagation and coalescence. Thermally-induced microcracks appear earlier in the more heterogeneous granite, which propagate and coalesce to form visible cracks earlier, leading to an earlier strength degradation. We also proposed an empirical formulation to predict the strength of granite with different grain size distribution and thermal environment. Our work is crucial for the site location and design of the deep geological repository since establishment of many construction parameters heavily depends on laboratory-determined properties of granite.
•Luhui granite specimens of various grain size grades after four high-temperature treatments are experimented.•Grain size heterogeneity controls the critical temperature at which a transition from strengthening to weakening occurs.•We propose an equation considering grain size distribution to predict the strength of granite exposed to high temperature.
This study presents a constitutive model to predict the shear behavior of rock joints under cyclic loading. The model focuses on asperity degradation and debris backfilling during a complete shear ...cycle. The degradation of two-order asperity is associated with the evolution of waviness and unevenness based on the classic wear theory. The produced debris significantly influences the joint shear behavior in the subsequent shear processes, and its thickness is dependent on shear displacement, joint length, as well as worn area and wavelength of asperities. The model particularly considers the dilation angles of waviness, unevenness, and backfilled debris at different processes during the shear cycle. The validation results show that the model can well predict the shear behavior of regularly shaped joints, but the accurate prediction for irregularly shaped joints depends on the quantitative description of joint surface roughness. The proposed model uses the quantitative description of joint profiles to evaluate the shear behavior of rock joints, which is more practical than previous models relying on empirical judgement or data back analysis.
Ground subsidence caused by underground coal mining is one of the challenging environmental issues in mining engineering. This paper presents a field monitoring study of longwall mining-induced ...ground subsidence in Shendong coalfield, China. The paper includes the subsidence data of four longwall panels, with mining and geological conditions varied. All the longwall faces have a high mining height (4.5-7 m) and extraction speed (9.0–13.3 m/day), but with shallow mining depth (180-210 m). High-frequency field observations allow the dynamic characteristics of the ground subsidence caused by high-intensity longwall mining to be captured and revealed. Results show that, for a longwall panel with a width to depth ratio of 1.35–1.6, the subsidence ratio is generally between 51.1–54.3%, and the maximum subsidence speed can reach 0.4 m/day. Furthermore, the overlying goaf considerably increases the subsidence ratio, and the instability of the boundary coal pillars decreases the ground surface deformation but increases the range of influence. Results also suggest the use of dynamic surface subsidence to infer the breakage and movement laws of the strata in the high-intensity longwall mining condition. Finally, the practical implications of the results and the associated environmental effects are briefly discussed.
Smart drug delivery nano-systems show significant changes in their physical or chemical properties in response to slight change in environmental physical and/or chemical signals, and further ...releasing drugs adjusted to the progression of the disease at the right target and rate intelligently. Two-dimensional materials possess dramatic status extend all over various scientific and technological disciplines by reason of their exceptional unique properties in application of smart drug delivery nano-systems. In this review, we summarized current progress to highlight various kinds of two-dimensional materials drug carriers which are widely explored in smart drug delivery systems as well as classification of stimuli responsive two-dimensional materials and the advantages and disadvantages of their applications. Consequently, we anticipate that this review might inspire the development of new two-dimensional materials with smart drug delivery systems, and deepen researchers’ understanding of smart nano-carries based on two-dimensional materials.
The fabrication, encapsulation, various stimuli response and applications of 2D materials smart drug delivery systems were reviewed. With unique 2D structure and sensitive response to external stimuli, 2D materials are expected to conquer any obstacle in maximizing the therapeutic effect of drugs. Display omitted
•Introduction to the exfoliation method of two-dimensional materials for biomedical applications.•Summary of the encapsulation of two-dimensional materials smart drug delivery systems.•Discussion of the classification of stimuli responsive two-dimensional materials smart drug delivery systems.•Overview of the application of two-dimensional materials smart drug delivery systems.
The transitional normal stress of a rock joint subject to shear refers to the critical normal stress under which the normal dilation is completely suppressed. The transitional normal stress is ...involved in many shear strength/constitutive models of joints as a key material constant; however, this parameter is poorly constrained and its determination is mostly empirical. Here we propose a simple formulation to predict the transitional normal stress based on the systematic, well-calibrated PFC2D (two-dimensional particle flow code) simulation of the shear characteristics of both sawtooth and JRC-profiled rock joints. In the PFC2D modelling, rock joints are confined by low to high normal stresses approximating the uniaxial compressive strength (joint wall compressive strength of fresh, dry and closely matched joints) of the simulated rock. The formulation can satisfactorily quantify the transitional normal stress of regular and irregular joint surfaces as a function of the rock strength and the joint surface roughness, as validated by the laboratory data. Therefore, it can be readily introduced to the shear strength criteria and constitutive models of rock joints, which could significantly promote the accurate quantification of rock joint shear behaviour.
Scale dependence of surface roughness of natural rock joints has long been an outstanding issue in rock mechanics. Controversial results were reported by various studies; however, the nature of scale ...dependency and the underlying mechanism for the conflicting observations remain unclear. Rock joints at different scales characterise two-order asperities, namely, waviness and unevenness; thus understanding how the individual roughness of waviness and unevenness vary as the joint size increases from the laboratory-scale to the large-scale is crucial for revealing the scale effect mystery. Here we digitise three natural granite joint surfaces with the same dimension of 1000 mm × 1000 mm through a high-resolution, three-dimensional scanner. Waviness and unevenness of each rock joint surface are quantitatively separated by selecting an appropriate sampling interval. The respective fractal dimensions of waviness and unevenness of joint surfaces sized from 100 mm × 100 mm to 1000 mm × 1000 mm are estimated through an improved roughness-length method. We find that the fractal dimensions of two-order roughness are scale-dependent but without generalised trends. The stationarity threshold beyond which the scale-dependency of roughness vanishes is absent for all the three joint samples, suggesting that the roughness of natural rock joints be assessed at the specific scale of the rock mass in-situ. We reveal that previous controversial results regarding scale effect are likely due to the composition of the roughness scaling of waviness and unevenness. Thus, accurate stability analysis of rock-engineering projects should consider separate contributions of multi-order asperities across scales to the strength and deformation of jointed rock masses.
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