Organisms are inherently three dimensional, thus comprehensive understanding of the complicated biological system requires analysis of organs or even whole bodies in the context of three dimensions. ...However, this is a tremendous task since the biological specimens are naturally opaque, a major obstacle in whole‐body and whole‐organ imaging. Tissue clearing technique provides a prospective solution and has become a powerful tool for three‐dimensional imaging and quantification of organisms. Tissue clearing technique aims to make tissue transparent by minimizing light scattering and light absorption, thus allowing deep imaging of large volume samples. When combined with diverse molecular labeling methods and high‐throughput optical sectioning microscopes, tissue clearing technique enables whole‐body and whole‐organ imaging at cellular or subcellular resolution, providing detailed and comprehensive information about the intact biological systems. Here, we give an overview of recent progress and biomedical applications of tissue clearing technique. We introduce the mechanisms and basic principles of tissue clearing, and summarize the current tissue clearing methods. Moreover, the available imaging techniques and software packages for data processing are also presented. Finally, we introduce the recent advances in applications of tissue clearing in biomedical fields. Tissue clearing contributes to the investigation of structure‐function relationships in intact mammalian organs, and opens new avenues for cellular and molecular mapping of intact human organs. We hope this review contributes to a better understanding of tissue clearing technique and can help researchers to select the best‐suited clearing protocol for their experiments.
Tissue clearing technique achieves tissue transparency by reducing light scattering and light absorption. Tissue clearing enables whole‐body and whole‐organ imaging and facilitates the understanding of intact organisms at system‐level. Tissue clearing contributes to the investigation of structure‐function relationships in intact mammalian organs, and opens new avenues for cellular and molecular mapping of intact human organs.
In order to study the recommendation system of digital media based on semantic classification, the CF-LFMC algorithm based on semantic classification is proposed. Firstly, the traditional algorithm ...is analyzed. Aiming at some problems existing in the traditional algorithm, a clustering algorithm model based on term meaning and collaborative filtering algorithm is designed by combining the collaborative filtering algorithm and project-based clustering algorithm. Before analyzing sparse data, the cold start and timeliness of the traditional algorithm are improved. Secondly, the performance comparison of three cosine similarity calculation methods of experimental IBCF algorithm, the performance comparison between CF-LFMC algorithm and IBCF algorithm, and the performance comparison between CF-LFMC algorithm and CF-LFMC algorithm without the time function is carried out. The clustering value N = 10 in the CF-LFMC algorithm is taken as the experimental result; MAE values of both algorithms decrease with the increase of the nearest neighbor number k. When the number of nearest neighbors is small, MAE values of the two algorithms are close to each other. As the number of nearest neighbors increases, the accuracy of the algorithm does not improve significantly, and the calculation cost of the algorithm will increase with the increase of the number of nearest neighbors, so the number of nearest neighbors between 20 and 30 is more appropriate. CF-LFMC shows better accuracy, and the CF-LFMC algorithm improved by the time function has improved the accuracy, which is better than the traditional algorithm in accuracy.
The major monoamine neurotransmitters, serotonin (5-HT) and catecholamines (i.e., norepinephrine (NE), epinephrine (E), and dopamine (DA)), are critical to the nervous system function, and imbalances ...of the neurotransmitters have been connected to a variety of diseases, making their measurement useful in a clinical setting. A simple, rapid, robust, sensitive, and specific LC-MS/MS method has been developed and validated for the simultaneous quantitation of urinary serotonin and catecholamines with low cost, which is ideal for routine clinical applications. A simple extraction from complex urine was accomplished using tailored solid phase extraction incorporating phenylboronic acid complexation on a 96-well HLB microplate for the sample extraction and resulted in significantly improved throughput, selectivity, and extraction recovery. Compared to 1–10 mL of urine typically used, this method required only 10 μL. A rapid chromatographic elution with a total cycle time of 6 min per sample compared to reported run times of 19–75 min was achieved on a PFP column. The sensitivity of l and 2 ng mL
−1
for the detection of low abundant E and NE combined with the high coverage of 1024 ng mL
−1
for DA enabled the multi-analyte detection of these biogenic amines in a single run. Good linearity (2.0–512, 1.0–512, 4.0–1024, and 4.0–1024 ng mL
−1
for NE, E, DA, and 5-HT, respectively), accuracy (87.6–104.0%), precision (≤8.0%), extraction recovery (69.6–103.7%), and matrix effect (87.1–113.1% for catecholamines and 63.6–71.4% for 5-HT) were obtained. No autosampler carryover was observed. The analytes were stable for 5 days at 20 °C, 14 days at 4 °C, and 30 days at −20 °C and five freeze–thaw cycles. The easy sample preparation, rapid LC, and multi-analyte MS detection allow two 96-well plates of samples to be extracted within 2 h and analyzed on an LC-MS/MS system within 24 h. The applicability and reliability of the assay were demonstrated by assessment of the reference interval for authentic urine specimens from 90 healthy individuals.
Graphical abstract
A simple, rapid, robust, sensitive and specific LC-MS/MS method combined with a dual functional solid phase extraction has been developed and validated for the simultaneous extraction and quantitation of monoamine neurotransmitters in human urine with low cost
Accurate quantitation of estrogens (i.e, estrone (E1), estradiol (E2) and estriol (E3)) is valuable for clinical assessment of human health and disease. Alterations in estrogen levels have been ...implicated in numerous pathological conditions. However, inadequacies in sensitivity and specificity, cumbersome sample preparation and invasive specimen collection hamper the usability of available methods for clinical applications. Herein, a simple, rapid, highly sensitive and specific LC-MS/MS method was developed and validated for the simultaneous determination of three estrogens in human saliva providing a non-invasive alternative to conventional blood samples. For the first time, a 96-well hydrophilic-lipophilic-balanced (HLB) microplate was employed for clean-up and enrichment of estrogens in a single extraction without the requirements of derivatization, evaporation, liquid-liquid extraction and online extraction. A rapid LC chromatographic separation with a turnaround time of 5.0min was achieved on a BEH C18 XP column. The use of 0.1mM ammonium fluoride (NH4F) as LC additive, and integration of summated and scheduled multiple reaction monitoring (MRM) transitions substantially improved the sensitivity to 1pg/mL, allowing the accurate quantitation of trace levels of three estrogens in one run. The assay was fully validated with good performance for extraction efficiency (67.0–85.6%), matrix effect (89.6–100.2%), linearity (from 1.0pg/mL up to 1000pg/mL), accuracy (98.9–112.4%) and precision (≤7.4%). Additionally, the assay was unaffected by 34 structurally-similar, potentially interfering substances tested at high clinical concentrations. The applicability of the assay was demonstrated by assessing the reference intervals of authentic saliva samples from healthy adult males, pre- and post-menopausal females. The easy sample preparation, fast LC and multi-analyte MS/MS detection utilizing noninvasive saliva as a specimen delivers a simple, practical, sensitive and accurate tool suitable for the high throughput measurement of E1, E2 and E3 in clinical laboratories.
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•Simultaneous LC-MS/MS quantitation of three estrogens in human saliva at 1pg/mL.•Easy, miniaturized and high throughput SPE without derivatization, evaporation or LLE.•Scheduled MRM summation and use of NH4F as LC additive for enhancing sensitivity.•Use noninvasive, cheap and stress-free saliva as an alternative matrix to blood.•Full method validation and application in authentic saliva samples.
Using the random phase approximation with both real space and discrete electron-hole (e-h) pair basis sets, we study the broadening of surface plasmons in metal structures of reduced dimensionality, ...where Landau damping is the dominant dissipation channel and presents an intrinsic limitation to plasmonics technology. We show that for every prototypical class of systems considered, including zero-dimensional nanoshells, one-dimensional coaxial nanotubes and two-dimensional ultrathin films, Landau damping can be drastically tuned due to energy quantization of the individual electron levels and e-h pairs. Both the generic trend and oscillatory nature of the tunability are in stark contrast with the expectations of the semiclassical surface scattering picture. Our approach also allows to vividly depict the evolution of the plasmons from the quantum to the classical regime, and to elucidate the underlying physical origin of hybridization broadening of nearly degenerate plasmon modes. These findings may serve as a guide in the future design of plasmonic nanostructures of desirable functionalities.
Catecholamines are a class of biogenic amines that play an important role as neurotransmitters and hormones. We developed and validated a rapid, specific and sensitive LC-MS/MS method for ...quantitative determination of catecholamines in human urine. Linearity, specificity, sensitivity, precision, accuracy, matrix effect, carryover, analyte stability, method comparison and reference range were evaluated. The catecholamine measurements were not affected by 35 structurally-related drugs and metabolites. The outstanding specificity was achieved by use of a specific diphenylborate-based solid phase extraction and subsequent selective LC-MS/MS analysis. Excellent sensitivity, accuracy and precision (average intra-assay variations <2.9 % and inter-assay variations <4.6 %) were obtained. The method was successfully applied in the study of day-to-day biological within- and between-subject variations of 25 healthy people under free-living conditions over three consecutive days. We observed that catecholamine excretions for second morning sampling had least day-to-day within-subject variation and excellent reproducibility. This work is one of the rare studies on these topics and represents the first utilization of advanced LC-MS/MS technology. Additionally, we found significant correlations between spot and conventional 24 h collections of human urine (n = 22, r > 0.853,
p
< 0.0001). These findings suggest that determining the catecholamine concentrations in the second morning urine sample presents accurate, convenient and reliable measurement of catecholamine excretions. In addition, consistent and significant diurnal variations for norepinephrine and epinephrine excretions were observed during the three-day period, while dopamine did not exhibit a diurnal rhythm. The LC-MS/MS method presented here is rapid, sensitive and specific, which could be an advantage in clinical laboratories.
Graphical Abstract
Diurnal variation of urinary catecholamines for 25 healthy people in three consecutive days
It remains a challenge to simultaneously quantify catecholamines and metanephrines in a simple, sensitive and cost-effective manner due to pre-analytical and analytical constraints. Herein, we ...describe such a method consisting of a miniaturized sample preparation and selective LC-MS/MS detection by the use of second morning spot urine samples. Ten microliters of second morning urine sample were subjected to solid phase extraction on an Oasis HLB microplate upon complexation with phenylboronic acid. The analytes were well-resolved on a Luna PFP column followed by tandem mass spectrometric detection. Full validation and suitability of spot urine sampling and biological variation were investigated. The extraction recovery and matrix effect are 74.1–97.3% and 84.1–119.0%, respectively. The linearity range is 2.5–500, 0.5–500, 2.5–1250, 2.5–1250 and 0.5–1250ng/mL for norepinephrine, epinephrine, dopamine, normetanephrine and metanephrine, respectively. The intra- and inter-assay imprecisions are ≤9.4% for spiked quality control samples, and the respective recoveries are 97.2–112.5% and 95.9–104.0%. The Deming regression slope is 0.90–1.08, and the mean Bland-Altman percentage difference is from −3.29 to 11.85 between a published and proposed method (n=50). A correlation observed for the spot and 24h urine collections is significant (n=20, p<0.0001, r: 0.84–0.95, slope: 0.61–0.98). No statistical differences are found in day-to-day biological variability (n=20). Reference intervals are established for an apparently healthy population (n=88). The developed method, being practical, sensitive, reliable and cost-effective, is expected to set a new stage for routine testing, basic research and clinical applications.
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•Simultaneous determination of urinary catecholamines and metanephrines by LC-MS/MS.•Miniaturized, specific and cost-saving SPE without pH adjustment and evaporation.•Drastically reduced urine sample volume required (10μL vs regular 500–1000μL).•Spot urine collection validated as an alternative to the conventional 24h urine.•Full validation and successful applications in authentic urine samples.
Next-generation non-volatile memories with ultrafast speed, low power consumption, and high density are highly desired in the era of big data. Here, we report a high performance memristor based on a ...Ag/BaTiO
/Nb:SrTiO
ferroelectric tunnel junction (FTJ) with the fastest operation speed (600 ps) and the highest number of states (32 states or 5 bits) per cell among the reported FTJs. The sub-nanosecond resistive switching maintains up to 358 K, and the write current density is as low as 4 × 10
A cm
. The functionality of spike-timing-dependent plasticity served as a solid synaptic device is also obtained with ultrafast operation. Furthermore, it is demonstrated that a Nb:SrTiO
electrode with a higher carrier concentration and a metal electrode with lower work function tend to improve the operation speed. These results may throw light on the way for overcoming the storage performance gap between different levels of the memory hierarchy and developing ultrafast neuromorphic computing systems.
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