Disparities among Black and White patients in plaque burden and composition and long-term impact

BACKGROUND

Black patients presenting to the catheterization laboratory have more risk factors and worse long-term outcomes. This sub-analysis of the Lipid Rich Plaque (LRP) study quantifies the plaque burden and composition of Black vs White patients and associated outcomes.

METHODS

Patients with a singular, self-reported race presenting for cardiac catheterization were enrolled if near-infrared spectroscopy/intravascular ultrasound (NIRS-IVUS) imaging of non-stented, non-culprit (NC) vessels was performed. Lipidic content was quantified at the 4-mm region with maximum Lipid Core Burden Index (maxLCBI4mm). NC major adverse cardiac events (NC-MACE) were defined as: cardiac death, cardiac arrest, non-fatal myocardial infarction, acute coronary syndrome, revascularization, and hospital readmission for angina with >20 % disease progression through 2 years.

RESULTS

Among 1346 patients with a singular, self-reported race, 182 were Black. Black vs White patients were more likely to be female, had higher rates of traditional risk factors, and were more likely to present acutely. Both patients and segments were more likely to have maxLCBI4mm > 400 (46.7 % vs 30.6 %, p < 0.001, respectively; 15.5 % vs 8.9 %, p < 0.001, respectively). Vessel size and plaque burden were larger for Black vs White patients. At 2 years, maxLCBI4mm > 400 and Black race were independently predictive of NC-MACE (hazard ratio [HR] maxLCBI4mm > 400: 2.37 [95 % confidence interval (CI) 1.50-3.76, p < 0.001], Black race: 2.8 [95 % CI 1.27-3.42, p = 0.004], pinteraction = 0.137).

CONCLUSIONS

Compared to White patients, Black patients had more lipid-rich plaques with greater plaque burden. Both high lipidic burden and Black race were independently predictive of NC-MACE within 2 years.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT02033694, NCT02033694.

A europium metal-organic framework for dual Fe3+ ion and pH sensing

Metal–organic frameworks (MOFs) with ratiometric sensing properties are desirable for many applications due to their intrinsic self-calibration. We report the re-assessment of the sensing properties of a MOF, originally reported as containing europium(III) and 2-hydroxyterephtalic acid, and having fluorescent ratiometric iron(III) sensing properties. Synchrotron single-crystal X-ray diffraction and proton nuclear magnetic resonance (¹H NMR) spectroscopy revealed that the MOF is composed of 2-methoxyterephthalate, not 2-hydroxyterephthalate as originally reported. We found that the MOF exhibits a sensor turn-off response towards Fe³⁺ ion concentrations in the range 0.5–3.7 ppm (band 425 nm), and a turn-on response towards a decrease of pH from 5.4 to 3.0 (band 375 nm), both resulting from the addition of acidic Fe³⁺ salt solution to a MOF suspension. Thus, the ratiometric sensing properties and the originally proposed mechanism no longer apply; our work reveals a dynamic quenching mechanism for the fluorescence turn-off response due to the presence of Fe³⁺ ions, and a ligand protonation mechanism for the turn-on response to a decrease in pH. Our work highlights the importance of a thorough investigation of the structure of any newly synthesized MOF, and, in the case of potential sensors, their selectivity and any environmental effects on their sensing behavior.

Near-infrared spectroscopy predicts events in men and women: Results from the Lipid Rich Plaque study

Background

The Lipid Rich Plaque (LRP) study demonstrated that near-infrared spectroscopy imaging of non-obstructive lesions identified patients and segments at higher risk for subsequent non-culprit major adverse cardiac events (NC-MACE). Whether this is true for both men and women is not known. In this post hoc analysis of the LRP study, we sought to investigate whether the maximum 4-mm Lipid Core Burden Index (maxLCBI_4mm) was of similar predictive value in men and women for NC-MACE.

Methods

Patients with an evaluable maxLCBI_4mm were stratified on the basis of sex at birth. A Cox proportional-hazards model was used to assess the predictive value of maxLCBI_4mm on future NC-MACE at the patient and plaque levels. The primary endpoint was cumulative incidence of NC-MACE at 24 months.

Results

Among 1271 patients, 388 (30.5%) were women. Women were older and had a higher cardiovascular risk profile. Cumulative incidence of NC-MACE at 24 months was 10.3% for women and 7.6% for men (log-rank p = 0.11). When comparing maxLCBI_4mm > 400 to maxLCBI_4mm ≤ 400, the hazard ratio (HR) for future NC-MACE was not significantly different between sexes: 2.10 (95% confidence interval [CI]: 1.28–3.44; p = 0.003) for men and 2.24 (95% CI: 1.18–4.28; p = 0.014) for women (p = 0.87). At the plaque level, the HR comparing maxLCBI_4mm > 400 to maxLCBI_4mm ≤ 400 was 3.49 (95% CI: 1.60–7.60, p = 0.002) for men and 4.79 (95% CI: 2.02–11.38, p < 0.001) for women, which was not significantly different (p = 0.57).

Conclusions

The maxLCBI_4mm was of similar predictive value for NC-MACE within 24 months in men and women.

Frequency of Lipid-Rich Coronary Plaques in Stable Angina Pectoris versus Acute Coronary Syndrome (from the Lipid Rich Plaque Study)

The multicenter prospective Lipid Rich Plaque (LRP) registry showed that nonculprit (NC) lipid-rich plaques identified by near-infrared spectroscopy (maxLCBI_4mm >400) with an intravascular ultrasound plaque burden (PB) >70% and/or minimum lumen area (MLA) <4 mm² within the maxLCBI_4mm segment were more frequently associated with major adverse cardiac events (MACE) within 2 years. The aim of this sub-study was to report the relationship between initial clinical presentation and subsequent NC-MACE. Patients enrolled in the LRP study were stratified post hoc as having a stable angina pectoris or silent ischemia presentation versus acute coronary syndrome, excluding patients presenting with acute ST-elevation myocardial infarction. Among the 1552 patients, 717 presented with stable angina pectoris or silent ischemia. Patients presenting with acute coronary syndrome were more likely to be younger and Black, current smokers, and have less chronic kidney disease. Of the scanned nonculprit vessels, there was no difference between the 2 clinical presentation groups regarding lipidic content, and the rate of lipid-rich plaques (maxLCBI_4mm >400) was 31.9% in both groups. Finally, there was no difference in NC-MACE at 2 years' follow-up, although within each group (stable versus acute coronary syndrome), the NC-MACE rate associated with maxLCBI_4mm >400 was significantly higher than maxLCBI_4mm ≤400 (stable 13.8% vs 6.5%; acute patients 11.6% vs 6.3%, respectively). In conclusion, in patient groups that present with stable angina pectoris or silent ischemia versus acute coronary syndrome, the NC lipidic content was similar, as was NC-MACE, through 2 years of follow-up.

Greater plaque burden and cholesterol content may explain an increased incidence of non-culprit events in diabetic patients: a Lipid-Rich Plaque substudy

AIMS 

Diabetes mellitus (DM) is associated with increased cardiovascular morbidity and mortality. The multicentre, prospective Lipid-Rich Plaque trial (LRP) examined non-culprit (NC) non-obstructive coronary segments with a combined near-infrared spectroscopy (NIRS)-intravascular ultrasound (IVUS) catheter. This study assessed the differences in NC plaque characteristics and their influence on major adverse cardiac events (MACE) in diabetic and non-diabetic patients.

METHODS AND RESULTS 

Patients with known DM status were divided into no diabetes, diabetes not treated with insulin (non-ITDM), and insulin-treated diabetes (ITDM). The association between presence and type of DM and NC-MACE was assessed at both the patient and coronary segment levels by Cox proportional regression modelling. Out of 1552 patients enrolled, 1266 who had their diabetes status recorded were followed through 24 months. Female sex, hypertension, chronic kidney disease, peripheral vascular disease, and high body mass index were significantly more frequent in diabetic patients. The ITDM group had more diseased vessels, at least one NC segment with a maxLCBI4 mm ≥400 in 46.2% of patients, and maxLCBI4 mm ≥400 in nearly one out of six Ware segments (15.2%, 125/824 segments). The average maxLCBI4 mm significantly increased from non-diabetic patients (NoDM) to non-insulin-treated diabetic patients (non-ITDM) to insulin-treated diabetic patients (ITDM; 137.7 ± 161.9, 154.8 ± 173.6, 182.9 ± 193.2, P < 0.001, respectively). In patients assigned to follow-up (692 ± 129 days), ITDM doubled the incidence of NC-MACE compared with the absence of diabetes (15.7% vs. 6.9%, P = 0.0008). The presence of maxLCBI4 mm>400 further increased the NC-MACE rate to 21.6% (Kaplan-Meier estimate).

CONCLUSION 

Cholesterol-rich NC plaques detected by NIRS-IVUS were significantly more frequent in diabetic patients, especially those who were insulin-treated, and were associated with an increased NC-MACE during follow-up.

Lipid-rich plaques detected by near-infrared spectroscopy predict coronary events irrespective of age: A Lipid Rich Plaque sub-study

BACKGROUND AND AIMS

In this Lipid Rich Plaque (LRP) sub-study, 1551 patients undergoing coronary angiography for acute coronary syndromes or stable angina were examined with near-infrared spectroscopy (NIRS) and intravascular ultrasound (IVUS). We aimed to assess the correlation of patient age with the presence of high-risk plaques, defined as maximum 4-mm Lipid Core Burden Index (maxLCBI_4mm) >400 and plaque burden >70%, and 2-year incidence of non-culprit major adverse cardiovascular events (NC-MACE).

METHODS

The study population was divided into four groups according to age: <50 years (122), 50-64 years (700), 65-74 years (502), and ≥75 years (227). The primary outcome was NC-MACE from index procedure to event or the end of the study. Cox regression and mixed-effects Cox regression models were used to assess the effect of age on the association between LCBI and NC-MACE at the patient and plaque levels.

RESULTS

Average maxLCBI_4mm and percentage of patients with at least one segment with maxLCBI_4mm > 400 were similar across the four age groups at both the patient and coronary segment levels. Having at least one segment with maxLCBI_4mm > 400 was strongly associated with NC-MACE, and that association did not differ significantly across age subgroups. Although less common (prevalence of 0.8%-1.3%), a similar trend toward greater NC-MACE rates was seen in patients with plaque burden >70% at the maximum LCBI site across age subgroups.

CONCLUSIONS

Lipid-rich plaques were as frequent in older as in younger patients and predicted a higher incidence of NC-MACE over 2-year follow-up irrespective of age.

Non-culprit MACE-rate in LRP: The influence of optimal medical therapy using DAPT and statins

BACKGROUND/PURPOSE

The Lipid Rich Plaque (LRP) study demonstrated the association between coronary plaque lipid content and outcomes. In this LRP substudy, we assessed the impact of optimal medical therapy (OMT) on the occurrence of non-culprit major adverse cardiac events (NC-MACE). Advanced intracoronary imaging modalities are able to identify patients with vulnerable coronary lesion morphology associated with future events.

METHODS/MATERIALS

A total of 1270 patients who underwent cardiac catheterization for suspected coronary artery disease (CAD) with evaluable maxLCBI_4mm in non-culprit vessels and known medical therapy after discharge were followed for 2 years. OMT was defined as the use of a statin and dual antiplatelet therapy (DAPT).

RESULTS

Among the 1270 patients included in this substudy, 1110 (87.7%) had PCI for an index event, and 1014 (80%) patients received OMT. Estimated cumulative incidence functions of NC-MACE did not differ significantly between patients treated with or without OMT (log-rank p-value = 0.876). In patients labeled high risk (maxLCBI_4mm > 400), cumulative incidence function also did not differ between patients treated with vs without OMT (log-rank p-value = 0.19).

CONCLUSIONS

In the current LRP analysis, we could not identify a beneficial effect of OMT in the reduction of NC-MACE rate, even in patients with high-risk plaques during 24-month follow-up.

Early-Stage Non-Small Cell Lung Cancer Stereotactic Body Radiation Therapy (SBRT) Outcomes in an Equal Access Military Setting

Introduction Lung stereotactic body radiation therapy (SBRT) is a first-line treatment for early-stage lung cancer in non-surgical candidates or those who refuse surgery. We compared our institutional outcomes from a unique patient population with decreased barriers to care with a recently published prospective series. Materials and methods  We retrospectively reviewed all patients who received definitive lung SBRT at the Walter Reed National Military Medical Center from 2015 to 2020. All patients underwent a positron emission tomography-computed tomography (PET-CT) and all were presented at a multidisciplinary tumor board. Patients were treated on a Trubeam linear accelerator (LINAC)-based system with daily cone-beam CT. The results were qualitatively compared to outcomes from prospective studies including RTOG 0236 and RTOG 0618. Results A total of 105 patients with 114 lesions were included. Median age was 77 years and 54.7% had ≥ 40-pack year smoking history. 36.8% did not have pathologic confirmation. With a median follow-up of 24 months, three-year local control (LC), disease-free survival (DFS) and overall survival (OS) rates were 92.4%, 81.0%, and 80.0%, respectively. Rates of Grade 1 and 2 toxicity were 21.9% and 6.7% and no patients experienced Grade ≥ 3 toxicity. Conclusions In our military setting with universal coverage and routine multidisciplinary care, lung SBRT provides outcomes comparable to prospective studies conducted at high-volume academic centers. More than one-third of patients were treated empirically without pathologic confirmation of disease, demonstrating a difference between clinical trials and community practice. Further investigation is warranted to integrate multidisciplinary management and achieve equal access to care to bridge existing health disparities in the community setting.

Microbial diversity and functional response to the redox dynamics of pyrite-rich sediment and the impact of preload surcharge

Microbial diversity and activities play pivotal biogeochemical roles in a redox-sensitive, pyrite-rich sediment's ecosystem. However, very little is known about the microbial community composition and distribution among the redox zones of pyrite-rich sediment and their response to changes caused by the burial of the sediment beneath compacted fill. In the present work, culture-independent, molecular phylogenetic investigations of the prokaryotic population and its diversity in a naturally occurring pyrite-rich sediment were undertaken to determine the microbial community composition, richness, diversity and distributions among the varying redox zones and their functional response to the imposition of surface surcharge, in the form of compacted fill. It was established that the pyrite-rich sediment is a redox-sensitive environment consisting of microhabitats with distinct and discontinuous physico-chemical characteristics, including DO, pH, Eh, temperature, electrical conductivity and salinity. It is a favourable environment for cyclic transformation of inorganic sulphur compounds and a unique environment for the habitation and growth of various microorganisms. Microbes adapted to the microhabitat and lived together in consortia, in response to their physiological and functional requirements. Microbes involved in the sulphur cycle had their populations concentrated in the oxic zone, while those involved in iron and carbon cycles were prevalent in the anoxic zones. As a result, highly diverse microbial populations occurred in isolated peaks within the sediment. The physico-chemical differences within the sediment changed in response to changes in the sediment redox dynamics. Imposition of the surcharge resulted in significant changes in the pH, temperature, Eh, DO, EC and salinity, reflecting marked re-distribution of the microbial population within the ecosystem. The cable bacteria phenomenon was evident in the sediment studied; however, there were doubt regarding their filamentous occurrence.

Anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment under preload surcharge

Pyrite undergoes oxidation when exposed to aqueous oxygen to produce acidic leachate with high concentrations of H⁺, SO₄^2-, and Fe³⁺. The oxidation mechanism is currently ascribed to contact between the mineral and aqueous oxygen. Consequently, management of acidic leachate from acid sulfate soils and acid mine drainage is focused on the prevention of contact between the sediment and aqueous oxygen through the surface. Intriguing though is the fact that in aquatic sediments, redox processes occur in sequence with the oxidizing agents. Among the common oxidants in aquatic sediments are O₂, [Formula: see text], Mn, and Fe, in the order of efficiency. Consequently, following the depletion of oxygen in pyrite-rich sediment, it would be expected that [Formula: see text], followed by Mn and then Fe, would continue the oxidation process. However, evidence of anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment is limited. Few studies have investigated the process in aquatic systems but mostly in laboratory experimental set ups. In this study, pyrite oxidation in a naturally occurring pyrite-rich sediment was investigated. A section of the sediment was covered with surface surcharge, in the form of compacted fill. The section of the sediment outside the surcharged area was preserved and used as control experiment. Solid phase soil and porewater samples were subjected to elemental, mineralogical, and microbial analyses. The results show excess accumulation of sulfate and sulfide in the anoxic zones of the original sediment and beneath the surcharge, accompanied by the disappearance of [Formula: see text], Mn, and Fe in the anoxic zones, indicating electron transfers between donors and acceptors, with pyrite as the most likely electron donor. The study outcome poses a significant challenge to the use of surface cover for the management of acidic leachate from pyrite oxidation, particularly, in areas rich in [Formula: see text], MnO^-₂, or Fe.

Copper Metallopolymer Catalyst for the Electrocatalytic Hydrogen Evolution Reaction (HER)

Conjugated polymers with stabilizing coordination units for single-site catalytic centers are excellent candidates to minimize the use of expensive noble metal electrode materials. In this study, conjugated metallopolymer, POS[Cu], was synthesized and fully characterized by means of spectroscopical, electrochemical, and photophysical methods. The copper metallopolymer was found to be highly active for the electrocatalytic hydrogen generation (HER) in an aqueous solution at pH 7.4 and overpotentials at 300 mV vs. reversible hydrogen electrode (RHE). Compared to the platinum electrode, the obtained overpotential is only 100 mV higher. The photoelectrochemical tests revealed that the complexation of the conjugated polymer POS turned its intrinsically electron-accepting (p-type) properties into an electron-donor (n-type) with photocurrent responses ten times higher than the organic photoelectrode.

The effect of biochar feedstock, pyrolysis temperature, and application rate on the reduction of ammonia volatilisation from biochar-amended soil

Ammonia (NH₃) volatilisation is one of the most important causes of nitrogen (N) loss in soil-plant systems worldwide. Carbon-based amendments such as biochar have been shown to mitigate NH₃ volatilisation in agricultural soils to various degrees. In this study, we investigated the influence of biochar feedstocks (poultry manure, green waste compost, and wheat straw), pyrolysis temperatures (250, 350, 450, 500 and 700°C) and application rates (1 and 2%), on NH₃ volatilisation from a calcareous soil. The 15 biochars were chemically characterized, and a laboratory incubation study was conducted to assess NH₃ volatilisation from the soil over a period of four weeks. Furthermore, changes to the bacterial and fungal communities were assessed via sequencing of phylogenetic marker genes. The study showed that biochar feedstock sources, pyrolysis temperature, and application rates all affected NH₃ volatilisation. Overall, low pyrolysis temperature biochars and higher biochar application rates achieved greater reductions in NH₃ volatilisation. A feedstock related effect was also observed, with poultry manure biochar reducing NH₃ volatilisation by an average of 53% in comparison to 38% and 35% reductions for biochar from green waste compost and wheat straw respectively. Results indicate that the biogeochemistry underlying biochar-mediated reduction in NH₃ volatilisation is complex and caused by changes in soil pH, NH₃ sorption and microbial community composition (especially ammonia oxidising guilds).

The impact of preload on the mobilisation of multivalent trace metals in pyrite-rich sediment

Trace metals occur at various concentrations in all wetlands. Their proliferation, chemical speciation, mobility and bioavailability are dependent on the redox potential (Eh), pH and the presence of organic and inorganic adsorption surfaces and co-precipitating metals. Consequently, changes in these key parameters have the potential to alter the fate of the dominant trace metal species in the sediment. An imposition of preload surcharge is a technique use in geotechnical engineering to improve in the strength and load carrying capacity of waterlogged sediments. The soil strength improvement is effected through the expulsion of porewater from the sediment. The imposition of surcharge over wetland sediments has the potential to create oxygen-deficient condition within the sediment, and cause pH, temperature, redox, EC and salinity changes in the sediment, which would impact on the mobilisation, chemical speciation, mobility and bioavailability of dominant toxic trace metals and their toxicity in the sediment. In the present work, a case study of the impact of preload surcharge on the proliferation, chemical speciation, mobilisation, mobility and bioavailability of arsenic, chromium, cobalt, copper and zinc in a naturally occurring pyrite-rich sediment is presented. The imposition of preload surcharge over the pyrite-rich sediment was accompanied by changes in the redox dynamics of the sediment, with multi-facet impact on the concentration, mobilisation and bioavailability of toxic trace metals, their redox transformation between oxidation states and on the toxicity within and outside the sediment environment.

Pilot study for supervised target detection applied to spatially registered multiparametric MRI in order to non-invasively score prostate cancer

BACKGROUND

Gleason Score (GS) is a validated predictor of prostate cancer (PCa) disease progression and outcomes. GS from invasive needle biopsies suffers from significant inter-observer variability and possible sampling error, leading to underestimating disease severity ("underscoring") and can result in possible complications. A robust non-invasive image-based approach is, therefore, needed.

PURPOSE

Use spatially registered multi-parametric MRI (MP-MRI), signatures, and supervised target detection algorithms (STDA) to non-invasively GS PCa at the voxel level.

METHODS AND MATERIALS

This study retrospectively analyzed 26 MP-MRI from The Cancer Imaging Archive. The MP-MRI (T2, Diffusion Weighted, Dynamic Contrast Enhanced) were spatially registered to each other, combined into stacks, and stitched together to form hypercubes. Multi-parametric (or multi-spectral) signatures derived from a training set of registered MP-MRI were transformed using statistics-based Whitening-Dewhitening (WD). Transformed signatures were inserted into STDA (having conical decision surfaces) applied to registered MP-MRI determined the tumor GS. The MRI-derived GS was quantitatively compared to the pathologist's assessment of the histology of sectioned whole mount prostates from patients who underwent radical prostatectomy. In addition, a meta-analysis of 17 studies of needle biopsy determined GS with confusion matrices and was compared to the MRI-determined GS.

RESULTS

STDA and histology determined GS are highly correlated (R = 0.86, p < 0.02). STDA more accurately determined GS and reduced GS underscoring of PCa relative to needle biopsy as summarized by meta-analysis (p < 0.05).

CONCLUSION

This pilot study found registered MP-MRI, STDA, and WD transforms of signatures shows promise in non-invasively GS PCa and reducing underscoring with high spatial resolution.

Analytical characterisation of nanoscale zero-valent iron: A methodological review

Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Both the mobility and reactivity of nZVI mainly depends on properties such as particle size, surface chemistry and bulk composition. In order to ensure efficient remediation, it is crucial to accurately assess and understand the implications of these properties before deploying these materials into contaminated environments. Many analytical techniques are now available to determine these parameters and this paper provides a critical review of their usefulness and limitations for nZVI characterisation. These analytical techniques include microscopy and light scattering techniques for the determination of particle size, size distribution and aggregation state, and X-ray techniques for the characterisation of surface chemistry and bulk composition. Example characterisation data derived from commercial nZVI materials is used to further illustrate method strengths and limitations. Finally, some important challenges with respect to the characterisation of nZVI in groundwater samples are discussed.

Concomitant reduction and immobilization of chromium in relation to its bioavailability in soils

In this study, two carbon materials [chicken manure biochar (CMB) and black carbon (BC)] were investigated for their effects on the reduction of hexavalent chromium [Cr(VI)] in two spiked [600 mg Cr(VI) kg(-1)] and one tannery waste contaminated [454 mg Cr(VI) kg(-1)] soils. In spiked soils, both the rate and the maximum extent of reduction of Cr(VI) to trivalent Cr [Cr(III)] were higher in the sandy loam than clay soil, which is attributed to the difference in the extent of Cr(VI) adsorption between the soils. The highest rate of Cr(VI) reduction was observed in BC-amended sandy loam soil, where it reduced 452 mg kg(-1) of Cr(VI), followed by clay soil (427 mg kg(-1)) and tannery soil (345 mg kg(-1)). X-ray photoelectron microscopy confirmed the presence of both Cr(VI) and Cr(III) species in BC within 24 h of addition of Cr(VI), which proved its high reduction capacity. The resultant Cr(III) species either adsorbs or precipitates in BC and CMB. The addition of carbon materials to the tannery soil was also effective in decreasing the phytotoxicity of Cr(VI) in mustard (Brassica juncea L.) plants. Therefore, it is concluded that the addition of carbon materials enhanced the reduction of Cr(VI) and the subsequent immobilization of Cr(III) in soils.

Determination of contact angles, silane coverage, and hydrophobicity heterogeneity of methylated quartz surfaces using ToF-SIMS

Methylated quartz surfaces are extensively used in colloid science for wettability studies and the control and impact of hydrophobicity in key physicochemical processes. In this study, time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to correlate the surface chemistry of trimethylchlorosilane-methylated quartz surfaces with the contact angle. Models have been developed for the calculation of both advancing and receding contact angles based on measurements of the ToF-SIMS signals for SiC(3)H(9)(+) (TMCS) and Si(+) (quartz). These models enable the contact angle across surfaces and, more importantly, that of individual particles to be determined on a micrometer scale. Distributions of contact angles in large ensembles of particles, therefore, can now be determined. In addition, from the ToF-SIMS analysis, the surface coverage of the methylated species can be quantitatively determined, in line with the Cassie equation. Moreover, advancing and receding contact angle maps can be calculated from ToF-SIMS images, and hence the variation in microscopic hydrophobicity (e.g., at the particle level) can be extracted directly from the images.

A new technique to examine individual pollutant particle and fibre deposition and transit behaviour in live mouse trachea

During respiration, particles suspended in the air are inhaled and unless cleared by airway defences they can remain and affect lung health. Their size precludes the use of standard imaging modalities so we have developed synchrotron phase-contrast X-ray imaging (PCXI) methods to non-invasively monitor the behaviour of individual particles in live mouse airways. In this study we used these techniques to examine post-deposition particle behaviour in the trachea. PCXI was used to monitor the deposition and subsequent behaviour of particles of quarry dust and lead ore; fibres of asbestos and fibreglass; and hollow glass micro-spheres. Visibility was examined in vitro and ex vivo to avoid the complicating effects of surrounding tissue and respiratory or cardiac motion. Particle behaviour was then examined after deposition onto the tracheal airway surfaces of live mice. Each particle and fibre looked and behaved differently on the airway surface. Particles lodged on the airway shortly after deposition, and the rate at which this occurred was dependent on the particle type and size. After the live-imaging experiments, excised airway samples were examined using light and electron microscopy. Evidence of particle capture into the airway surface fluids and the epithelial cell layer was found. PCXI is a valuable tool for examining post-deposition particulate behaviour in the tracheal airway. These first indications that the interaction between airways and individual particles may depend on the particle type and size should provide a novel approach to studying the early effects of respired particles on airway health.