Characterising the chemical and physical properties of phase-change nanodroplets.

Phase-change nanodroplets have attracted increasing interest in recent years as ultrasound theranostic nanoparticles. They are smaller compared to microbubbles and they may distribute better in tissues (e.g. in tumours). They are composed of a stabilising shell and a perfluorocarbon core. Nanodroplets can vaporise into echogenic microbubbles forming cavitation nuclei when exposed to ultrasound. Their perfluorocarbon core phase-change is responsible for the acoustic droplet vaporisation. However, methods to quantify the perfluorocarbon core in nanodroplets are lacking. This is an important feature that can help explain nanodroplet phase change characteristics. In this study, we fabricated nanodroplets using lipids shell and perfluorocarbons. To assess the amount of perfluorocarbon in the core we used two methods, 19F NMR and FTIR. To assess the cavitation after vaporisation we used an ultrasound transducer (1.1 MHz) and a high-speed camera. The 19F NMR based method showed that the fluorine signal correlated accurately with the perfluorocarbon concentration. Using this correlation, we were able to quantify the perfluorocarbon core of nanodroplets. This method was used to assess the content of the perfluorocarbon of the nanodroplets in solutions over time. It was found that perfluoropentane nanodroplets lost their content faster and at higher ratio compared to perfluorohexane nanodroplets. The high-speed imaging indicates that the nanodroplets generate cavitation comparable to that from commercial contrast agent microbubbles. Nanodroplet characterisation should include perfluorocarbon concentration assessment as critical information for their development.

Oceanic and atmospheric anomalies associated with extreme precipitation events in China 1983-2020.

Observed synoptic anomalies in connection with China's extreme precipitation events/floods in the summers of 1982/83, 1997/98, 2010, 2014, 2015/16, and 2020 are studied. These events mainly occur within the middle and lower Yangtze basins. The dominant moisture source is the Northern Indian Ocean and the Southwestern Pacific Ocean of the Indo-Pacific warm pool (IPWP). Both of these bodies of water have warmed since 1979. In East Asia, the strong land-sea thermal contrast driven by global warming drives the increased East Asian summer monsoon (EASM) circulation, which develops deep convective precipitation. The total precipitable water in the Indo-Pacific region has also been increasing since 1979. The intense southwest Indian monsoon transports moist air to the Yangtze basin in mid-June and forms the Meiyu (plum rain) front. Strengthened Okhotsk/Ural blocking highs in East and West Asia, as well as the Western Pacific subtropical high (WPSH) and the South Asian high (SAH) over south Eurasia, remain stationary for long periods and interact to exacerbate the precipitation. The western edge of the WPSH expands westward towards East Asia to transport moisture. To the north, the WPSH combines with the two blocking highs to trigger more rain. The intensified SAH expands eastward and merges with the extended WPSH to add rain. On the other hand, rainfall is modulated by the El Niño-Southern Oscillation (ENSO), notably in relation to the super El Niño events in 1982-1983, 1997-1998, 2015-2016, and 2020. The research described in this paper highlights changes in the weather systems with warming and, in particular, the enormous and dominating impact of the warming and expanding IPWP on rainfall extremes. Improved seasonal forecasts and planning ahead will protect lives and livelihoods.

Label-free study of intracellular glycogen level in metformin and resveratrol-treated insulin-resistant HepG2 by live-cell FTIR spectroscopy.

Conventional in vitro study often involves the destruction of the cells followed by purification and dilution steps before applying enzymatic assay or metabolomic analysis. It is a costly and laborious process, and it cannot monitor changes as a function of time. Recently, we have developed a new label-free live-cell FTIR approach that can directly measure biochemical compositional changes within living cells in situ and the spectral changes are shown to be highly specific to the drug applied. In this work, we have demonstrated for the first time the effect of two anti-diabetic drugs, metformin and Resveratrol, on insulin-resistant liver cells (HepG2). Using live-cell FTIR with principal component analysis, we have shown the differences in the biochemical profiles between normal and insulin-resistant cells (p < 0.05), the lack of response/difference from the insulin-resistant cell to insulin (p > 0.05) and the restoration of the biochemical profile and sensitivity to insulin from the insulin-resistant cells after the drug treatment (p < 0.05). Particularly, a rise in the glycogen level, marked by three distinctive peaks at 1150, 1080 and 1020 cm-1, within the living cells after the anti-diabetic drug treatments is observed. The live-cell FTIR results are confirmed by a parallel gold-standard biochemical assay, demonstrating the restoration of insulin sensitivity of the insulin-resistance cells. Live-cell FTIR can be a complementary tool for drug efficacy screening, especially for insulin sensitizers.

Immediate effects of transcutaneous electrical nerve stimulation on gait patterns in chronic stroke survivors: A single group, pretest-posttest clinical trial.

BACKGROUND: Transcutaneous electrical nerve stimulation (TENS) has been used to reduce muscle spasticity and improve locomotion in stroke survivors. We speculate that acute changes in gait performance after TENS mediate functional improvement in the long-term. However, no previous study has investigated the effect of TENS on ankle kinetics and kinematics during walking in stroke survivors. PURPOSE: We aimed to investigate whether TENS applied over the paretic leg could rapidly improve the plantar flexion moment and ankle kinematics in chronic stroke survivors with lower limb paresis. METHODS: Twenty chronic stroke survivors were recruited. They underwent 30 min of TENS over the area innervated by the common peroneal nerve on the paretic leg. Three-dimensional (3D) motion capture was performed and ankle plantar flexor spasticity was assessed before and immediately after stimulation. Ankle kinematics and kinetic and spatiotemporal data were collected using 3D motion capture. Ankle plantar flexor spasticity was assessed using the Modified Tardieu Scale. PRINCIPAL RESULTS: A significant increase in the ankle plantar flexion moment of the paretic side during the pre-swing phase was observed immediately after stimulation (p = 0.009, maximal mean difference = 0.035, 95%CI = 0.0125 to 0.0575). The step length of the paretic limb also increased significantly after stimulation (p = 0.023, mean difference = -0.02, 95%CI = -0.04 to -0.004). TENS had no immediate effect on paretic ankle spasticity, as measured by the Modified Tardieu Scale, or on other temporo-spatial parameters. CONCLUSION: The findings support the use of TENS to improve the motor function and gait pattern in chronic stroke survivors. The study indicated that the application of TENS to the paretic leg before gait training might improve rehabilitation outcomes. Future studies investigating the effects of TENS on functional outcomes, the optimal stimulation duration, and assessing spasticity using more sensitive measures are warranted.

Amino acid hydrotropes to increase the solubility of indomethacin and carbamazepine in aqueous solution.

A number of amino acids (AA) has been investigated as promising hydrotropes to improve the solubility of biopharmaceutics classification system (BCS) class II drugs carbamazepine (CBZ) and indomethacin (IND) via specific complexations in aqueous solution. The aim of this work is to understand the molecular basis of these hydrotropic interactions by investigating the two model drugs combined with 12 amino acids including phenylalanine, tryptophan, isoleucine, proline, valine, glycine, serine, threonine, arginine, lysine, histidine and aspartic acid in water at 25 °C, 30 °C and 45 °C. The amino acids were chosen based on their different side chains (neutral aromatic, aliphatic, polar charged or uncharged) to investigate their hydrotropic performance. A linear solubility curve was observed between indomethacin and mono-neutral hydrophobic amino acids (phenylalanine, tryptophan, isoleucine, proline and valine) well beyond 1:1 molar ratio indicating the interaction is predominantly non-ionic between the drug and the hydrotropes. Interestingly, the aqueous solubility of carbamazepine (a neutral compound) was enhanced by neutral, charged basic or acidic amino acids, confirming the presence of hydrophobic interactions that involve H-bonds, H/π and π/π stacking and the results were confirmed by UV-Vis spectroscopy. A combination of multiple neutral amino acids showed additive hydrotropic effect in indomethacin solubility with up to 7-folds increases. This study demonstrates for the first time the potential of amino acids as hydrotropes to improve aqueous solubility of poorly water-soluble drugs, which is important for pharmaceutical development.

In vitro Fourier transform infrared spectroscopic study of the effect of glycerol on the uptake of beclomethasone dipropionate in living respiratory cells.

The quantification of drug in living cells is of increasing interest in pharmaceutical research because of its importance in understanding drug efficacy and toxicity. Label-free in situ measurement methods are advantageous for their ability to obtain chemical and time profiles without the need of labelling or extraction steps. We have previously shown that Fourier transform infrared (FTIR) spectroscopy has the potential to quantify drug in situ within living cells at micromolar level when a simple solution of drug was added to the medium. The purpose of this study was to demonstrate that the approach can evaluate more complex systems such as the effect of membrane modification by a formulation on drug uptakes. The inhaled corticosteroid, beclomethasone dipropionate (BDP), in Calu-3 respiratory epithelial cells in the absence and presence of glycerol, an excipient in some inhaled medicines was used as the model system. The FTIR method was first validated for limit of detection (LOD) and quantification (LOQ) according to published guidelines and the LOQ was found to be âˆ¼ 20 µM, good enough to quantify BDP in the living cell. The uptake of BDP by living Calu-3 cells was found to be reduced in the presence of glycerol as expected due to the stiffening of the cell membrane by the presence of glycerol in the formulation. This study demonstrates the valuable analytical capability of live-cell FTIR to study the effect of formulation on drug transport in lungs and to evaluate drug availability to intracellular targets. We conclude that FTIR has potential to contribute widely at the frontier of live-cell studies.

Live-cell ATR-FTIR spectroscopy as a novel bioanalytical tool for cell glucose metabolism research.

Current novel drug developments for the treatment of diabetes require multiple bioanalytical assays to interrogate the cellular metabolism, which are costly, laborious and time-consuming. Fourier-transform infrared (FTIR) spectroscopy is a nondestructive, label-free, sensitive and low-cost technique that is recently found to be suitable for studying living cells. The aim of this study is to demonstrate that live-cell FTIR can be applied to study the differences in glucose metabolism in cells in normal culturing medium and cells treated in high glucose (a diabetes model) in order to highlight the potential of the technique in diabetes research. Live HepG2 cells were treated in normal glucose (3.8 mM; control) or high glucose (25 mM) medium and were measured directly using the FTIR approach. Principal component analysis was used to highlight any possible correlated changes 24, 48 and 72 h after treatments. FTIR spectra of live cell treated in normal and high glucose medium have shown significant differences (p < 0.05) for all treatment time. The control cells have seen an increased in the absorbance at 1088, 1240 and 1400 cm-1, which are associated with phosphate stretching mode vibrations from phosphorylated proteins and DNA back bone; and symmetric stretching mode vibration of COO- from fatty acids, amino acids, lipids and carbohydrate metabolites. However, the high glucose treated cells have shown a different changes in the 1000-1200 cm-1 region, which is linked to the glycogen and ATP:ADP ratio. In conclusion, live-cell FTIR can be a low-cost method for the studies of metabolic changes in cells.

Tracking glycosylation in live cells using FTIR spectroscopy.

This is the first demonstration of the study of glycan protein turnover in living cells by FTIR with commercially available tetraacetylated N-Azidoacetyl-D-Mannosamine (Ac4ManNAz) label. The FTIR analysis has shown to be able to monitor the metabolism of glycans in living cells in real time. The method is simple, quantitative and requires equipment that are available in many laboratories. It can be used in a wide range of applications such as the study of glycosylation and cell-signalling.

Atmospheric microplastic deposition in an urban environment and an evaluation of transport.

Microplastics are a global environmental issue contaminating aquatic and terrestrial environments. They have been reported in atmospheric deposition, and indoor and outdoor air, raising concern for public health due to the potential for exposure. Moreover, the atmosphere presents a new vehicle for microplastics to enter the wider environment, yet our knowledge of the quantities, characteristics and pathways of airborne microplastics is sparse. Here we show microplastics in atmospheric deposition in a major population centre, central London. Microplastics were found in all samples, with deposition rates ranging from 575 to 1008 microplastics/m2/d. They were found in various shapes, of which fibrous microplastics accounted for the great majority (92%). Across all samples, 15 different petrochemical-based polymers were identified. Bivariate polar plots indicated dependency on wind, with different source areas for fibrous and non-fibrous airborne microplastics. This is the first evidence of airborne microplastics in London and confirms the need to include airborne pathways when consolidating microplastic impacts on the wider environment and human health.

Questionnaire survey on medical futility and termination of resuscitation in cardiac arrest patients among emergency physicians in Hong Kong.

INTRODUCTION: The perceptions of medical futility and decisions about termination of resuscitation (TOR) for out-of-hospital cardiac arrest (OHCA) are highly heterogeneous and dependent on the practice of the attending emergency physicians. The objective of this study was to report and investigate the knowledge, attitudes, and practices regarding medical futility and TOR during management of OHCA in Hong Kong. METHODS: A cross-sectional survey was conducted among emergency medicine physicians in Hong Kong. The questionnaire assessed participants' background, knowledge, attitudes, and behaviours concerning medical futility and TOR in management of OHCA. Composite scores were calculated to reflect knowledge, attitudes, and practices of OHCA treatment. Subgroup analysis and multiple regression analysis were used to explore the relationship between participants' background, knowledge, attitudes, and behaviours. RESULTS: The response rate to this survey was 57% (140/247). Independent predictors of less aggressive resuscitation in OHCA patients included status as a Fellow of the Hong Kong College of Emergency Medicine (ß= -0.314, P=0.028) and being an Advanced Cardiac Life Support instructor (ß= -0.217, P=0.032). There was no difference in aggressiveness of resuscitation in terms of years of clinical experience (ß=0.015, P=0.921), knowledge of TOR (ß=0.057, P=0.509), or attitudes about TOR (ß= -0.103, P=0.214). The correlation between knowledge and attitudes was low (Spearman's coefficient=0.02, P=0.795). CONCLUSION: Clinical practice and behaviour of TOR was not demonstrated to have associations with knowledge or attitude. Status as a Fellow of the Hong Kong College of Emergency Medicine or Advanced Cardiac Life Support instructor were the only two parameters identified that had significant relationships with earlier TOR in medically futile patients with OHCA.

Influence of Urban Green Space and Facility Accessibility on Exercise and Healthy Diet in Hong Kong.

Background A cross-sectional study using a convenience sampling method was conducted to understand how green space and accessibility of common public open spaces in compact urban areas affect physical activity and healthy diets of residents. Methods A total of 554 residents completed a structured questionnaire on quality of life, physical activity level and healthy eating practice. Particularly, categories of physical activity and durations were obtained by using the short form Chinese International Physical Activity Questionnaire (IPAQ-C), then the Metabolic Equivalent of Task (MET)-minutes/week was calculated using the formulae (walking minutes × walking days × 3.3) + (moderate-intensity activity minutes × moderate days × 4.0) + (vigorous-intensity activity minutes × vigorous-intensity days × 8.0). The percentage of green space was calculated based on a spatial buffer with a 500 m radius from participants' geocoded addresses using a SPOT ('Satellite Pour l'Observation de la Terre' in French) satellite image-derived vegetation dataset. Parks, promenade and sports facilities were examples of open spaces. Results The sampled population who lived with green space averaged 10.11% ± 7.95% (ranged 1.56-32.90%), with the majority (90%) performing physical activities at medium and high levels. MET-minutes/week was significantly associated (Pearson r = 0.092; p < 0.05) with the green space percentage. Relatively active residents commonly used open spaces within the district for performing exercise, in particular, parks and promenades were mostly used by older residents, while sports facilities by the younger groups at age 25-44 and <25 years. Conclusions Current findings suggested promotion of exercise could be achieved by the design or redesign of built environment to include more parks accessible to the residents with the increase of vegetation.

Towards identifying the mode of action of drugs using live-cell FTIR spectroscopy.

Fourier transform infrared spectroscopy (FTIR) has been shown to be a promising tool for identifying the mode of action of drugs. However, most previous studies have focused on the analysis of fixed or dried cells. The measurement of living cells has the advantage of obtaining time series data, and the in situ approach eliminates the need for fixing or drying the cells. In this study, the potential of live-cell FTIR method for the identification of the mode of action of drugs was demonstrated. Four different drugs were tested, with two of the drugs having the same mode of action (tamoxifen and toremifene) and the other two having different modes of action (imatinib and doxorubicin). Live cells were treated in the four drugs at and below the IC50 level (i.e. the concentration of drug required to inhibit the growth of cells by 50%), and the changes to their spectra after the addition of drugs were monitored over a 24-hour period. Principal component analysis (PCA) of the spectral data shows that drugs with different modes of action are well-separated, while the drugs with the same mode of action are grouped together. The results also show that at IC50, the separation appears to be the clearest at 2 hours for imatinib and tamoxifen/toremifene and 6 hours for doxorubicin. However, at 50% of the IC50 drug concentration, the separation appears to be the best at longer incubation time, i.e. 24 hours, for all four drugs. In conclusion, live-cell FTIR has shown to be able to distinguish and group spectral signatures of cells treated with drugs of known modes of action after a relatively short time of exposure. Further collection of live-cell data would enable an algorithm to be developed for the prediction of the modes of action of novel drugs, which can help in the preclinical drug screening process.

Subcellular mapping of living cells via synchrotron microFTIR and ZnS hemispheres.

FTIR imaging is a label-free, non-destructive method valuably exploited in the study of the biological process in living cells. However, the long wavelength/low spatial resolution and the strong absorbance of water are still key constrains in the application of IR microscopy ex vivo. In this work, a new retrofit approach based on the use of ZnS hemispheres is introduced to significantly improve the spatial resolution on live cell FTIR imaging. By means of two high refractive index domes sandwiching the sample, a lateral resolution close to 2.2 µm at 6 µm wavelength has been achieved, i.e. below the theoretical diffraction limit in air and more than twice the improvement (to ~λ/2.7) from our previous attempt using CaF2 lenses. The ZnS domes also allowed an extended spectral range to 950 cm-1, in contrast to the cut-off at 1050 cm-1 using CaF2. In combination with synchrotron radiation source, microFTIR provides an improved signal-to-noise ratio through the circa 12 µm thin layer of medium, thus allowing detailed distribution of lipids, protein and nucleic acid in the surround of the nucleus of single living cells. Endoplasmic reticula were clearly shown based on the lipid ν(CH) and ν(C=O) bands, while the DNA was imaged based on the ν(PO2-) band highlighting the nucleus region. This work has also included a demonstration of drug (doxorubicin) in cell measurement to highlight the potential of this approach. Graphical abstract.

A combined FTIR and DSC study on the bilayer-stabilising effect of electrostatic interactions in ion paired lipids.

Investigating lipid ion pair formation is important for understanding the mechanisms of lipid-mediated drug resistance in bacteria. In this study we have used the charged amphiphiles dipalmitoylphosphatidylglycerol (DPPG) and dihexadecyldimethylammonium bromide (DHDAB), as a model to evaluate the formation of ion pairs by a combined Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analysis. FTIR was employed to study the environment of the DPPC headgroup phosphate and lipid/surfactant alkane chains, in vesicles formed by the two amphiphiles mixed in various molar ratios. An increase of the absorbance ratio of 1221-1201 cm-1 in the asymmetric phosphate stretching mode was found to follow a sigmoidal relationship with the proportion of DHDAB, increasing to a plateau above a DPPG/DHDAB 1:1 molar ratio of, providing evidence that the PG headgroup phosphate is involved in ion pairing. A consistent red shift was measured for the position of the symmetric CH2 stretch band for the lipid/surfactant 1:1 molar ratio mixture, which is indicative of an increased ordering of the hydrophobic chains. The DSC experiments yielded information about the thermotropic and the mixing behaviour of the lipid/surfactant systems. DPPG and DHDAB seem to form an ion pair with cluster compound characteristics at the equimolar ratio. Most interestingly, the DPPG/DHDAB 2:1 molar ratio mixture is characterized by strong intermolecular interactions, which result in a pronounced stabilization of the gel phase, possibly through the formation of a closely-associated ion triplet configuration in which the charges are delocalised across the headgroups.

Observations of tropospheric aerosols and NO2 in Hong Kong over 5years using ground based MAX-DOAS.

In this paper, we present long term observations of atmospheric aerosols and nitrogen dioxide (NO2) in Hong Kong using a Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument. Ground based MAX-DOAS measurements were performed over 5years from December 2010 to November 2015. Vertical distribution profiles of aerosols and NO2 were derived from MAX-DOAS O4 and NO2 observations by applying the optimal estimation method. Retrieved MAX-DOAS measurements of aerosols and NO2 show good agreement with sun photometer observation of aerosol optical depths (AODs) and long path DOAS measurement of ground level NO2 mixing ratios. Tropospheric vertical column densities (VCDs) of NO2 derived from MAX-DOAS measurements are used to validate OMI satellite NO2 observations. Daily data show reasonably good agreement with each other with Pearson correlation coefficient R=0.7. However, MAX-DOAS NO2 VCDs are on average higher than OMI observations by a factor of 2. Introducing aerosols in the air mass factor calculation would enhance the OMI VCDs by 7-13%, the remaining discrepancy is mainly due to the differences in spatial coverage between the two instruments. Diurnal variation patterns of aerosols and NO2 indicated significant contributions from local anthropogenic emissions. Analysis of air mass transport shows that the enhancement of surface aerosols and NO2 concentrations mainly results from accumulation of local emissions under low wind speed conditions.