Cell-penetrating peptides noncovalently modified red phosphorescent nanoparticles for high-efficiency imaging.

The application of long-lived phosphorescence probes in time-resolved luminescence imaging is limited by their low quantum yield in aqueous solutions. However, sensitization of thermally activated delayed fluorescence (TADF) materials can compensate for this limitation while addressing the issue of insufficient proportion of their own long lifetime. In this study, we utilized the characteristics of phosphorescence and TADF materials simultaneously by doping the receptor iridium complex PMD-Ir into the donor TADF polymer PCzDP-20 through donor-receptor doping method, and successfully prepared highly efficient red phosphorescent nanoparticles. The quantum yield of the nanoparticles obtained by this method reaches up to 30%, and the luminescence lifetime can reach several thousand nanoseconds. Additionally, due to the low concentration doping of PMD-Ir, the risk of transition metal toxicity is greatly reduced. Furthermore, we used non-covalent modification with amphiphilic cell-penetrating peptides (CPPs) to increase the cell membrane permeability of the nanoparticles. The CPPs modified nanoparticles achieve in vivo confocal imaging of zebrafish and intracellular time-resolved imaging by its significantly improved bioimaging capabilities. The functional nanoparticles designing method fully utilizes the characteristics of PMD-Ir, PCzDP-20, and CPPs, solving the problems of low quantum yield and poor membrane permeability of Ir-complex nanoparticles. This will greatly promote the development of time-resolved luminescence imaging.

Effects of lane-change scenarios on lane-change decision and eye movement.

Improper lane-change manoeuvre can cause traffic safety issues and even lead to serious traffic collisions. Quantifying the decision behaviour and eye movements can provide a deeper understanding of lane-change manoeuvre in vehicle interaction environment. The purpose of this study was to investigate the effect of lane-change scenarios defined by gaps on lane-change decision and eye movements. Twenty-eight participants were recruited to complete a naturalistic driving experiment. Eye movements and lane-change decision duration (LDD) were recorded and analysed. Results suggested that the scanning frequency (SF) and saccade duration (SD) were the sensitive parameters to respond to lane-change scenarios. LDD was significantly affected by the scenario, SF, and SD. The increase in LDD was related to the high difficulty gap and high frequency scanning of multiple regions. These findings evaluated the driver's decision performance in response to different lane-change environments and provided valuable information for measuring the driver's scenario perception ability.Practitioner summary: A naturalistic driving experiment was conducted to evaluate the interaction of lane-change decision, eye movement, and lane changing gap in a lane-change task. The results reveal the sensitive eye movement parameters to lane-change scenario, which provide guidelines for driver's perception ability test and professional driver assessment.

Dual-Channel Fluorescent Probe for Detecting Viscosity and ONOO- without Signal Crosstalk in Nonalcoholic Fatty Liver.

Nonalcoholic fatty liver disease (NAFLD) is a global health issue. Peroxynitrite and liver viscosity have recently been found to be potential biomarkers of NAFLD. Therefore, it is of great significance to develop dual-response fluorescent probes for simultaneous detecting peroxynitrite and viscosity. We report herein a new probe (CQ) that can simultaneously detect peroxynitrite and viscosity at two independent fluorescent channels without signal crosstalk. CQ shows high selectivity, rapid response, good water solubility, low cytotoxicity, and mitochondrial localization properties. In particular, CQ responds sensitively to viscosity and peroxynitrite with off-on fluorescence changes at 710 and 505 nm, respectively. The wavelength gap between these two channels is more than 200 nm, ensuring that there is no signal crosstalk during detection. With this property, the probe was applied to simultaneously detect mitochondrial viscosity and peroxynitrite and image the changes of liver viscosity and peroxynitrite concentration during the pathogenesis of NAFLD. All results show that the CQ probe is a powerful tool for simultaneous detection of viscosity and peroxynitrite and provides a potential new diagnostic method for NAFLD.

Polarity-Sensitive Cell Membrane Probe Reveals Lower Polarity of Tumor Cell Membrane and Its Application for Tumor Diagnosis.

Cancer is a health threat worldwide, and it is urgent to develop more sensitive cancer detection methods. Herein, a polarity-sensitive cell membrane probe (named COP) was developed for detecting cancer cells and tumors sensitively and selectively at the cell membrane level. The probe shows a strong polarity-dependent fluorescence and excellent cell membrane targeting ability to visualize cell membrane with red fluorescence with a non-washing process. Notably, COP can selectively light up the tumor cell membranes, which reveals that cancer cell membranes have lower polarity than normal cell membranes. The giant unilamellar vesicle model and cell imaging studies proved this. Moreover, COP can effectively and selectively light up tumors. Overall, this work demonstrates that the polarity of the tumor cell membrane is quite different to normal cell membranes, and based on this, sensitive membrane probes can be developed to selectively visualize cancer cells and tumors, which opens up a new way for tumor diagnosis at the cellular level.

Two Water-Soluble and Wash-Free Fluorogenic Probes for Specific Lighting Up Cancer Cell Membranes and Tumors.

The construction of microenvironment-sensitive probes with good cell membrane-targetability can reveal the fundamental properties of cell membranes. Herein, two polarity-sensitive probes, termed MEMs were reported for the first time to specifically light up cancer cell membranes. Both probes were designed with tetrahydroquinoxaline coumarin amide as the fluorophore, and quaternary ammonium groups were appended to increase water solubility and target cell membranes. In vitro studies showed that the fluorescence of both probes displayed strong polarity dependence and had a wide linear range to polarity (Δf). MEMs also displayed excellent cell membrane targeting ability and could long-term light up cell membranes with red fluorescence and a wash-free process. More excitingly, MEMs could specifically light up cancer cell membranes, revealing that cancer cells might have lower cell membrane polarity than normal cells. In vivo studies showed that MEMs could also effectively distinguish tumors from normal tissues. Overall, this work has not only developed two polarity-sensitive probes with good cell membrane targetability, but also provided new insights and methods for an in-depth understanding of cancer cells and cancer diagnosis.

Near-Infrared Mitochondria-Targetable Fluorescent Probe for High-Contrast Bioimaging of H2S.

To elucidate the complex role of biological H2S and study the mitochondrial damage and some related diseases, effective methods for visualization of H2S in mitochondria and in vivo are urgently needed. In this contribution, a novel near-infrared mitochondria-targetable fluorescence probe MI-H2S for H2S detection was developed. MI-H2S shows rapid detection ability for H2S in pure aqueous solution and outputs a highly selective and sensitive fluorescence-on signal at 663 nm with a large Stokes shift of 141 nm. Bioimaging experiments revealed that the probe has good mitochondrial-targeting ability and high-contrast imaging ability for detecting H2S in living systems. The probe also showed great potential in the detection of H2S during inflammation. All of the results demonstrate that MI-H2S can be applied as an effective probe for the visualization and study of H2S in mitochondria and in vivo.

Real-time tracking lysosomal pH changes under heatstroke and redox stress with a novel near-infrared emissive probe.

Lysosomes are important subcellular organelles with acidic pH. The change of lysosomal pH can affect the normal function and activity of cells. To conveniently detect and visualize lysosomal pH changes, we designed herein a novel fluorescent probe NIR-Rh-LysopH. The probe is based on a Rhodamine 101 derivative, which was modified to include a fused tetrahydroquinoxaline ring to obtain near-infrared fluorescence and a methylcarbitol moiety to locate the lysosome. Based on the proton-induced spirolactam ring-opening mechanism, NIR-Rh-LysopH showed rapid, selective, sensitive, and reversible near-infrared fluorescence responses around 686 nm (Stokes shift 88 nm) with a pKa value of 5.70. From pH 7.4 to 4.0, about 285 folds of fluorescence enhancement was observed. Cell experiments showed that NIR-Rh-LysopH has low cytotoxicity and excellent lysosome-targeting ability. Moreover, NIR-Rh-LysopH was applied successfully to track lysosomal pH changes induced by drugs (such as chloroquine and dexamethasone), heatstroke, and redox stress. Thus, NIR-Rh-LysopH is very promising for conveniently tracking lysosomal pH changes and studying the related life processes.

Impacts of COVID-19 on urban rail transit ridership using the Synthetic Control Method.

The outbreak of COVID-19 in 2020 has had drastic impacts on urban economies and activities, with transit systems around the world witnessing an unprecedented decline in ridership. This paper attempts to estimate the effect of COVID-19 on the daily ridership of urban rail transit (URT) using the Synthetic Control Method (SCM). Six variables are selected as the predictors, among which four variables unaffected by the pandemic are employed. A total of 22 cities from Asia, Europe, and the US with varying timelines of the pandemic outbreak are selected in this study. The effect of COVID-19 on the URT ridership in 11 cities in Asia is investigated using the difference between their observed ridership reduction and the potential ridership generated by the other 11 cities. Additionally, the effect of the system closure in Wuhan on ridership recovery is analyzed. A series of placebo tests are rolled out to confirm the significance of these analyses. Two traditional methods (causal impact analysis and straightforward analysis) are employed to illustrate the usefulness of the SCM. Most Chinese cities experienced about a 90% reduction in ridership with some variation among different cities. Seoul and Singapore experienced a minor decrease compared to Chinese cities. The results suggest that URT ridership reductions are associated with the severity and duration of restrictions and lockdowns. Full system closure can have severe impacts on the speed of ridership recovery following resumption of service, as demonstrated in the case of Wuhan with about 22% slower recovery. The results of this study can provide support for policymakers to monitor the URT ridership during the recovery period and understand the likely effects of system closure if considered in future emergency events.

A novel reaction-based fluorescence probe for rapid imaging of HClO in live cells, animals, and injured liver tissues.

Hypochlorous acid (HClO) is an important bioactive molecule, playing vital roles in a large number of physiological and pathological processes. Abnormal concentration of HClO in vivo has close contact with many diseases including inflammatory diseases and cancer. For bioimaging HClO, a new colorimetric and turn-on near-infrared (NIR) fluorescence probe (DDAO-ClO) was designed and synthesized in this work through a specific reaction of HClO with dimethylthiocarbamate. DDAO-ClO proved to show distinct and highly selective colorimetric and NIR fluorescence responses for HClO with fast response time (<3 s) and high sensitivity (LOD = 7.3 nM) in vitro. After confirming the excellent in vitro sensing ability, imaging HClO with DDAO-ClO in living HeLa cells, MCF-7 cells, zebrafish, and mice was all successfully demonstrated. And with this probe, it was further discovered that more endogenous HClO was produced in injured mice liver tissues, which demonstrates that DDAO-ClO not only is effective for in vivo detection of HClO but also has a broad application prospect.

Aggregation-induced emission and solid fluorescence of fluorescein derivatives.

We report herein for the first time that the aggregation-induced emission and strong solid fluorescence of fluorescein derivatives can be realized by slightly modifying their structure, which provides a new option for AIEgens and solid fluorescent materials.

CO release with ratiometric fluorescence changes: a promising visible-light-triggered metal-free CO-releasing molecule.

The first visible-light-triggered metal-free and ratiometric fluorescent CORM is reported. This CORM can be used to release CO with distinct ratiometric fluorescence changes in aqueous solution, living cells, zebrafish, and mice, which provided an excellent controllable and trackable CORM for living systems.

A Fluorescent ESIPT Probe for Imaging CO-Releasing Molecule-3 in Living Systems.

CO-releasing molecule-3 (CORM-3) has been widely used recently as a convenient and safe CO donor to release exogenous CO in living cells and to study the effects of CO on cellular systems. Accordingly, development of effective methods for detecting and tracking CORM-3 in living systems is of great significance. In this work, a readily available fluorescent probe for detection of CORM-3 was reported for the first time. This probe is based on an excited-state intramolecular proton transfer (ESIPT) dye phthalimide and uses the reducing ability of CORM-3 to convert a nitro group to an amino group, and more importantly, it can be used for rapid, highly selective, and sensitive detection of CORM-3 with a distinct turn-on green fluorescence change in aqueous solution, living cells, and animals, thus providing a useful tool for studying CORM-3 in living systems.

A dual-channel probe with green and near-infrared fluorescence changes for in vitro and in vivo detection of peroxynitrite.

In this study, a coumarin-semirhodamine hybrid based dual-channel fluorescent probe was developed for detection of peroxynitrite. This probe works well in nearly pure aqueous solution and displays a rapid, highly sensitive and selective response for peroxynitrite at two different emission wavelengths (700 and 515 nm, respectively), along with distinct color and green to near-infrared fluorescence changes. The fluorescent intensity ratio at 700 and 515 nm increases linearly with the concentration of peroxynitrite from 0 to 50 µM, and the detection limit is estimated to be 59 nM. Moreover, bioimaging of exogenous and endogenous peroxynitrite in living cells and in vivo detection of peroxynitrite with this probe at dual fluorescence channels were all successfully applied. The results suggest that this new probe can be used as a useful imaging tool for studying peroxynitrite in vitro and in vivo.

Allyl Fluorescein Ethers as Promising Fluorescent Probes for Carbon Monoxide Imaging in Living Cells.

Recently, the fluorescent detection of carbon monoxide (CO) in living cells has attracted great attention. However, due to the lack of effective ways to construct fluorescent CO probes, fluorescent detection of CO in living cells is still in its infancy. In this paper, we report for the first time the use of allyl ether as a reaction site for construction of fluorescent CO probes. By this way, two readily available allyl fluorescein ethers were prepared, which were found to be highly selective and sensitive probes for CO in the presence of PdCl2. These probes have the merits of good stability, good water-solubility, and rapid and distinct colorimetric and remarkable fluorescent turn-on signal changes. Moreover, a very low dose of these two probes can be used to detect and track CO in living cells, indicating that these two probes could be very promising biological tools for CO detection in living systems. Overall, this work provided not only two new promising fluorescent CO probes but also a new way to devise fluorescent CO probes.

Readily Available Fluorescent Probe for Carbon Monoxide Imaging in Living Cells.

Carbon monoxide (CO) is an important gasotransmitter in living systems and its fluorescent detection is of particular interest. However, fluorescent detection of CO in living cells is still challenging due to lack of effective probes. In this paper, a readily available fluorescein-based fluorescent probe was developed for rapid detection of CO. This probe can be used to detect CO in almost wholly aqueous solution under mild conditions and shows high selectivity and sensitivity for CO with colorimetric and remarkable fluorescent turn-on signal changes. The detection limit of this probe for CO is as low as 37 nM with a linear range of 0-30 µM. More importantly, this probe (1 µM dose) can be conveniently used for fluorescent imaging CO in living cells.

Analysis of bus passenger comfort perception based on passenger load factor and in-vehicle time.

Although bus comfort is a crucial indicator of service quality, existing studies tend to focus on passenger load and ignore in-vehicle time, which can also affect passengers' comfort perception. Therefore, by conducting surveys, this study examines passengers' comfort perception while accounting for both factors. Then, using the survey data, it performs a two-way analysis of variance and shows that both in-vehicle time and passenger load significantly affect passenger comfort. Then, a bus comfort model is proposed to evaluate comfort level, followed by a sensitivity analysis. The method introduced in this study has theoretical implications for bus operators attempting to improve bus service quality.

Risk factors affecting fatal bus accident severity: Their impact on different types of bus drivers.

While the bus is generally considered to be a relatively safe means of transportation, the property losses and casualties caused by bus accidents, especially fatal ones, are far from negligible. The reasons for a driver to incur fatalities are different in each case, and it is essential to discover the underlying risk factors of bus fatality severity for different types of drivers in order to improve bus safety. The current study investigates the underlying risk factors of fatal bus accident severity to different types of drivers in the U.S. by estimating an ordered logistic model. Data for the analysis are retrieved from the Buses Involved in Fatal Accidents (BIFA) database from the USA for the years 2006-2010. Accidents are divided into three levels by counting their equivalent fatalities, and the drivers are classified into three clusters by the K-means cluster analysis. The analysis shows that some risk factors have the same impact on different types of drivers, they are: (a) season; (b) day of week; (c) time period; (d) number of vehicles involved; (e) land use; (f) manner of collision; (g) speed limit; (h) snow or ice surface condition; (i) school bus; (j) bus type and seating capacity; (k) driver's age; (l) driver's gender; (m) risky behaviors; and (n) restraint system. Results also show that some risk factors only have impact on the "young and elder drivers with history of traffic violations", they are: (a) section type; (b) number of lanes per direction; (c) roadway profile; (d) wet road surface; and (e) cyclist-bus accident. Notably, history of traffic violations has different impact on different types of bus drivers.