Recurrent myocardial infarction and emergency department visits: a retrospective study on the Stockholm Area Chest Pain Cohort.

BACKGROUND: Patients who experience acute myocardial infarction (AMI) are at risk of recurrent AMI. Contemporary data on recurrent AMI and its association with return emergency department (ED) visits for chest pain are needed. METHODS: This Swedish retrospective cohort study linked patient-level data from six participating hospitals to four national registers to construct the Stockholm Area Chest Pain Cohort (SACPC). The AMI cohort included SACPC participants visiting the ED for chest pain diagnosed with AMI and discharged alive (first primary diagnosis of AMI during the study period not necessarily the patient's first AMI). The rate and timing of recurrent AMI events, return ED visits for chest pain and all-cause mortality were determined during the year following index AMI discharge. RESULTS: Among 1 37 706 patients presenting to the ED with chest pain as principal complaint from 2011 to 2016, 5.5% (7579/137 706) were hospitalised with AMI. In total, 98.5% (7467/7579) of patients were discharged alive. In the year following index AMI discharge, 5.8% (432/7467) of AMI patients experienced ≥1 recurrent AMI event. Return ED visits for chest pain occurred in 27.0% (2017/7467) of index AMI survivors. During a return ED visit, recurrent AMI was diagnosed in 13.6% (274/2017) of patients. One-year all-cause mortality was 3.1% in the AMI cohort and 11.6% in the recurrent AMI cohort. CONCLUSIONS: In this AMI population, 3 in 10 AMI survivors returned to the ED for chest pain in the year following AMI discharge. Furthermore, over 10% of patients with return ED visits were diagnosed with recurrent AMI during that visit. This study confirms the high residual ischaemic risk and associated mortality among AMI survivors.

The REACT study: design of a randomized phase 3 trial to assess the efficacy and safety of clazosentan for preventing deterioration due to delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

BACKGROUND: For patients presenting with an aneurysmal subarachnoid hemorrhage (aSAH), delayed cerebral ischemia (DCI) is a significant cause of morbidity and mortality. The REACT study is designed to assess the safety and efficacy of clazosentan in preventing clinical deterioration due to DCI in patients with aSAH. METHODS: REACT is a prospective, multicenter, randomized phase 3 study that is planned to enroll 400 patients with documented aSAH from a ruptured cerebral aneurysm, randomized 1:1 to 15 mg/hour intravenous clazosentan vs. placebo, in approximately 100 sites and 15 countries. Eligible patients are required to present at hospital admission with CT evidence of significant subarachnoid blood, defined as a thick and diffuse clot that is more than 4 mm in thickness and involves 3 or more basal cisterns. The primary efficacy endpoint is the occurrence of clinical deterioration due to DCI up to 14 days post-study drug initiation. The main secondary endpoint is the occurrence of clinically relevant cerebral infarction at Day 16 post-study drug initiation. Other secondary endpoints include the modified Rankin Scale (mRS) and the Glasgow Outcome Scale-Extended (GOSE) score at Week 12 post-aSAH, dichotomized into poor and good outcome. Radiological results and clinical endpoints are centrally evaluated by independent committees, blinded to treatment allocation. Exploratory efficacy endpoints comprise the assessment of cognition status at 12 weeks and quality of life at 12 and 24 weeks post aSAH. DISCUSSION: In the REACT study, clazosentan is evaluated on top of standard of care to determine if it reduces the risk of clinical deterioration due to DCI after aSAH. The selection of patients with thick and diffuse clots is intended to assess the benefit/risk profile of clazosentan in a population at high risk of vasospasm-related ischemic complications post-aSAH. TRIAL REGISTRATION (ADDITIONAL FILE 1): ClinicalTrials.gov (NCT03585270). EU Clinical Trial Register (EudraCT Number: 2018-000241-39).

Longitudinal neuropsychological assessment after aneurysmal subarachnoid hemorrhage and its relationship with delayed cerebral ischemia: a prospective Swiss multicenter study.

OBJECTIVE: While prior retrospective studies have suggested that delayed cerebral ischemia (DCI) is a predictor of neuropsychological deficits after aneurysmal subarachnoid hemorrhage (aSAH), all studies to date have shown a high risk of bias. This study was designed to determine the impact of DCI on the longitudinal neuropsychological outcome after aSAH, and importantly, it includes a baseline examination after aSAH but before DCI onset to reduce the risk of bias. METHODS: In a prospective, multicenter study (8 Swiss centers), 112 consecutive alert patients underwent serial neuropsychological assessments (Montreal Cognitive Assessment [MoCA]) before and after the DCI period (first assessment, < 72 hours after aSAH; second, 14 days after aSAH; third, 3 months after aSAH). The authors compared standardized MoCA scores and determined the likelihood for a clinically meaningful decline of ≥ 2 points from baseline in patients with DCI versus those without. RESULTS: The authors screened 519 patients, enrolled 128, and obtained complete data in 112 (87.5%; mean [± SD] age 53.9 ± 13.9 years; 66.1% female; 73% World Federation of Neurosurgical Societies [WFNS] grade I, 17% WFNS grade II, 10% WFNS grades III-V), of whom 30 (26.8%) developed DCI. MoCA z-scores were worse in the DCI group at baseline (-2.6 vs -1.4, p = 0.013) and 14 days (-3.4 vs -0.9, p < 0.001), and 3 months (-0.8 vs 0.0, p = 0.037) after aSAH. Patients with DCI were more likely to experience a decline of ≥ 2 points in MoCA score at 14 days after aSAH (adjusted OR [aOR] 3.02, 95% CI 1.07-8.54; p = 0.037), but the likelihood was similar to that in patients without DCI at 3 months after aSAH (aOR 1.58, 95% CI 0.28-8.89; p = 0.606). CONCLUSIONS: Aneurysmal SAH patients experiencing DCI have worse neuropsychological function before and until 3 months after the DCI period. DCI itself is responsible for a temporary and clinically meaningful decline in neuropsychological function, but its effect on the MoCA score could not be measured at the time of the 3-month follow-up in patients with low-grade aSAH with little or no impairment of consciousness. Whether these findings can be extrapolated to patients with high-grade aSAH remains unclear. Clinical trial registration no.: NCT03032471 (ClinicalTrials.gov).

The P2Y12 Receptor Antagonist Selatogrel Dissolves Preformed Platelet Thrombi In Vivo.

Selatogrel, a potent and reversible antagonist of the P2Y12 receptor, inhibited FeCl3-induced thrombosis in rats. Here, we report the anti-thrombotic effect of selatogrel after subcutaneous applications in guinea pigs and mice. Selatogrel inhibited platelet function only 10 min after subcutaneous application in mice. In addition, in a modified Folts thrombosis model in guinea pigs, selatogrel prevented a decrease in blood-flow, indicative of the inhibition of ongoing thrombosis, approximately 10 min after subcutaneous injection. Selatogrel fully normalised blood flow; therefore, we speculate that it may not only prevent, but also dissolve, platelet thrombi. Thrombus dissolution was investigated using real-time intravital microscopy in mice. The infusion of selatogrel during ongoing platelet thrombus formation stopped growth and induced the dissolution of the preformed platelet thrombus. In addition, platelet-rich thrombi were given 30 min to consolidate in vivo. The infusion of selatogrel dissolved the preformed and consolidated platelet thrombi. Dissolution was limited to the disintegration of the occluding part of the platelet thrombi, leaving small mural platelet aggregates to seal the blood vessel. Therefore, our experiments uncovered a novel advantage of selatogrel: the dissolution of pre-formed thrombi without the disintegration of haemostatic seals, suggesting a bipartite benefit of the early application of selatogrel in patients with acute thrombosis.

Position-controlled quantum emitters with reproducible emission wavelength in hexagonal boron nitride.

Single photon emitters (SPEs) in low-dimensional layered materials have recently gained a large interest owing to the auspicious perspectives of integration and extreme miniaturization offered by this class of materials. However, accurate control of both the spatial location and the emission wavelength of the quantum emitters is essentially lacking to date, thus hindering further technological steps towards scalable quantum photonic devices. Here, we evidence SPEs in high purity synthetic hexagonal boron nitride (hBN) that can be activated by an electron beam at chosen locations. SPE ensembles are generated with a spatial accuracy better than the cubed emission wavelength, thus opening the way to integration in optical microstructures. Stable and bright single photon emission is subsequently observed in the visible range up to room temperature upon non-resonant laser excitation. Moreover, the low-temperature emission wavelength is reproducible, with an ensemble distribution of width 3 meV, a statistical dispersion that is more than one order of magnitude lower than the narrowest wavelength spreads obtained in epitaxial hBN samples. Our findings constitute an essential step towards the realization of top-down integrated devices based on identical quantum emitters in 2D materials.

Identifying early pulmonary arterial hypertension biomarkers in systemic sclerosis: machine learning on proteomics from the DETECT cohort.

Pulmonary arterial hypertension (PAH) is a devastating complication of systemic sclerosis (SSc). Screening for PAH in SSc has increased detection, allowed early treatment for PAH and improved patient outcomes. Blood-based biomarkers that reliably identify SSc patients at risk of PAH, or with early disease, would significantly improve screening, potentially leading to improved survival, and provide novel mechanistic insights into early disease. The main objective of this study was to identify a proteomic biomarker signature that could discriminate SSc patients with and without PAH using a machine learning approach and to validate the findings in an external cohort.Serum samples from patients with SSc and PAH (n=77) and SSc without pulmonary hypertension (non-PH) (n=80) were randomly selected from the clinical DETECT study and underwent proteomic screening using the Myriad RBM Discovery platform consisting of 313 proteins. Samples from an independent validation SSc cohort (PAH n=22 and non-PH n=22) were obtained from the University of Sheffield (Sheffield, UK).Random forest analysis identified a novel panel of eight proteins, comprising collagen IV, endostatin, insulin-like growth factor binding protein (IGFBP)-2, IGFBP-7, matrix metallopeptidase-2, neuropilin-1, N-terminal pro-brain natriuretic peptide and RAGE (receptor for advanced glycation end products), that discriminated PAH from non-PH in SSc patients in the DETECT Discovery Cohort (average area under the receiver operating characteristic curve 0.741, 65.1% sensitivity/69.0% specificity), which was reproduced in the Sheffield Confirmatory Cohort (81.1% accuracy, 77.3% sensitivity/86.5% specificity).This novel eight-protein biomarker panel has the potential to improve early detection of PAH in SSc patients and may provide novel insights into the pathogenesis of PAH in the context of SSc.

Thick and diffuse cisternal clot independently predicts vasospasm-related morbidity and poor outcome after aneurysmal subarachnoid hemorrhage.

OBJECTIVE: Aneurysmal subarachnoid hemorrhage (aSAH) is associated with significant morbidity and mortality. The presence of thick, diffuse subarachnoid blood may portend a worse clinical course and outcome, independently of other known prognostic factors such as age, aneurysm size, and initial clinical grade. METHODS: In this post hoc analysis, patients with aSAH undergoing surgical clipping (n = 383) or endovascular coiling (n = 189) were pooled from the placebo arms of the Clazosentan to Overcome Neurological Ischemia and Infarction Occurring After Subarachnoid Hemorrhage (CONSCIOUS)-2 and CONSCIOUS-3 randomized, double-blind, placebo-controlled phase 3 studies, respectively. Patients without and with thick, diffuse SAH (≥ 4 mm thick and involving ≥ 3 basal cisterns) on admission CT scans were compared. Clot size was centrally adjudicated. All-cause mortality and vasospasm-related morbidity at 6 weeks and Glasgow Outcome Scale-Extended (GOSE) scores at 12 weeks after aSAH were assessed. The effect of the thick and diffuse cisternal aSAH on vasospasm-related morbidity and mortality, and on poor clinical outcome at 12 weeks, was evaluated using logistic regression models. RESULTS: Overall, 294 patients (51.4%) had thick and diffuse aSAH. Compared to patients with less hemorrhage burden, these patients were older (median age 55 vs 50 years) and more often had World Federation of Neurosurgical Societies (WFNS) grade III-V SAH at admission (24.1% vs 16.5%). At 6 weeks, all-cause mortality and vasospasm-related morbidity occurred in 36.1% (95% CI 30.6%-41.8%) of patients with thick, diffuse SAH and in 14.7% (95% CI 10.8%-19.5%) of those without thick, diffuse SAH. Individual event rates were 7.5% versus 2.5% for all-cause death, 19.4% versus 6.8% for new cerebral infarct, 28.2% versus 9.4% for delayed ischemic neurological deficit, and 24.8% versus 10.8% for rescue therapy due to cerebral vasospasm, respectively. Poor clinical outcome (GOSE score ≥ 4) was observed in 32.7% (95% CI 27.3%-38.3%) and 16.2% (95% CI 12.1%-21.1%) of patients with and without thick, diffuse SAH, respectively. CONCLUSIONS: In a large, centrally adjudicated population of patients with aSAH, WFNS grade at admission and thick, diffuse SAH independently predicted vasospasm-related morbidity and poor 12-week clinical outcome. Patients with thick, diffuse cisternal SAH may be an important cohort to target in future clinical trials of treatment for vasospasm.

Thick and Diffuse Subarachnoid Blood as a Treatment Effect Modifier of Clazosentan After Subarachnoid Hemorrhage.

Background and Purpose- Clazosentan, an endothelin receptor antagonist, has been shown to reduce angiographic vasospasm and vasospasm-related morbidity after aneurysmal subarachnoid hemorrhage (SAH), although no effect on long-term functional outcome has been demonstrated. Thick clot on initial computed tomography is associated with an increased risk of vasospasm and delayed cerebral ischemia. In this post hoc analysis, we hypothesized that use of clazosentan in this subpopulation would provide stronger benefit. Methods- We analyzed SAH patients enrolled in the CONSCIOUS-2 and CONSCIOUS-3 studies (Clazosentan to Overcome Neurological Ischemia and Infarction Occurring After Subarachnoid Hemorrhage) and compared the effects of clazosentan 5 mg/h, 15 mg/h, and placebo starting the day after aneurysm repair. The analysis was performed separately based on the presence or absence of thick (≥4 mm) and diffuse (≥3 cisterns) SAH on admission computed tomography. The primary composite end point was all-cause mortality and vasospasm-related morbidity at 6 weeks, and the main secondary end point was the extended Glasgow Outcome Scale at 3 months, adjusted for admission clinical grade. Results- Of 1718 randomized patients, 919 (53%) had thick and diffuse SAH. The primary composite end point in this group occurred in 36% of placebo-treated patients (n=294), 30% patients treated with clazosentan 5 mg/h (n=514; relative risk, 0.82; 95% CI, 0.67-0.99), and 19% patients treated with clazosentan 15 mg/h (n=111; relative risk, 0.54; 95% CI, 0.36-0.80). Despite this, death or poor functional outcome (Glasgow Outcome Scale ≤4) occurred in 33% of placebo-treated patients, 34% of patients treated with clazosentan 5 mg/h (relative risk 1.02; 95% CI, 0.84-1.23), and 35% of patients treated with clazosentan 15 mg/h (relative risk 1.14; 95% CI, 0.88-1.48). Conclusions- In an enriched population with thick and diffuse SAH, clazosentan at a dose of 5 and 15 mg/h was able to significantly reduce vasospasm-related morbidity in a dose-dependent manner. The absence of an effect on long-term functional status likely reflects the complexity and multiplicity of factors that contribute to poor outcome after SAH. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT00558311; NCT00940095.

Reversal of Vasospasm with Clazosentan After Aneurysmal Subarachnoid Hemorrhage: A Pilot Study.

BACKGROUND: Clazosentan, an endothelin-1 receptor antagonist, has been shown to prevent the development of large vessel angiographic vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). It has been hypothesized that clazosentan can also reverse established angiographic vasospasm. METHODS: The REVERSE (resynchronization reverses remodeling in systolic left ventricular dysfunction) study was a prospective, multicenter, open-label, 2-stage pilot study of adult patients with aSAH who had received intravenous clazosentan (15 mg/hour) after developing moderate-to-severe angiographic vasospasm. The primary efficacy endpoint was the reversal of global cerebral vasospasm in large cerebral artery segments 3 hours after clazosentan initiation. The secondary endpoints included large artery vasospasm reversal at 24 hours and the maximum change in the angiographic cerebral circulation time. The change in vasospasm severity in the proximal and distal segments was investigated in an exploratory analysis. RESULTS: The primary efficacy endpoint was met in 3 of 11 evaluable patients (27.3%; 95% confidence interval, 6.0-61.0). However, recruitment was stopped after stage 1 in accordance with the predefined interim analysis criteria. In the exploratory analysis, 50.0% and 77.8% of the patients showed a significant reversal of vasospasm or improvement to the admission state in ≥2 distal segments at 3 and 24 hours and 28.6% and 77.8% in ≥2 proximal segments, respectively. CONCLUSIONS: Although the main analysis showed a reversal of large vessel vasospasm 3 hours after clazosentan initiation in a few patients, the exploratory analysis indicated a clear pharmacodynamic dilating effect on vasospastic cerebral vessels at 24 hours in most patients, in particular, in the distal arterial beds. This observation supported the inclusion of patients with established vasospasm in the ongoing REACT (prevention and treatment of vasospasm with clazosentan) trial.

[The valproate model of autism]. / Les modèles animaux d'étude de l'autisme - Le modèle « valproate ¼.

Autism is a neuro-developmental pathology affecting 1 out of 100 children worldwide. The trauma and social consequences induced by autism are a real public health issue. Clinically, autism is characterized primarily by communications and social interactions deficits associated with repetitive behaviors and restricted interests. The term of autism spectrum disorders (ASD) is used to account for the diversity of symptoms that characterize this pathology. Based on observations made in humans, a rodent (rats and mice) model of autism was obtained and validated by prenatal exposure to sodium valproate. Using this model, mechanisms that concern both the functioning of neural networks and the properties of neurons have been proposed to account for some disorders that characterize autism. This model is also widely used in pre-clinical studies to evaluate new therapies against ASD.

Regional and sex-dependent alterations in Purkinje cell density in the valproate mouse model of autism.

Neuropathological and neuroimaging studies indicate a decrease in Purkinje cell (PC) density in the cerebellum of autistic patients and rodent models of autism. Autism is far more prevalent in males than females, and sex-specific properties of PCs have been reported recently. We investigated the differential sensitivity of PCs in the valproate acid (VPA) mouse model of autism by estimating the linear density of PCs immununolabelled with calbindin in the cerebellum of males and females. Whereas prenatal VPA treatment surprisingly increased PC linear density in both sexes 13 days after birth (P13), it significantly reduced the linear density of PCs in the cerebellum of 40-day-old (P40) males, but not females. In males, PC loss was more pronounced in the posterior part of the cerebellum and was significant in the VIth, VIIth, IXth and paramedian lobules. In females, PC loss was restricted to the paramedian lobule. These results suggest that this sex-specific sensitivity of PCs to VPA may contribute towards the motor disturbances and behavioural abnormalities observed in autism.

Maturation of GABAergic Transmission in Cerebellar Purkinje Cells Is Sex Dependent and Altered in the Valproate Model of Autism.

Brain development is accompanied by a shift in gamma-aminobutyric acid (GABA) response from depolarizing-excitatory to hyperpolarizing-inhibitory, due to a reduction of intracellular chloride concentration. This sequence is delayed in Autism Spectrum Disorders (ASD). We now report a similar alteration of this shift in the cerebellum, a structure implicated in ASD. Using single GABAA receptor channel recordings in cerebellar Purkinje cells (PCs), we found two conductance levels (18 and 10 pS), the former being dominant in newborns and the latter in young-adults. This conductance shift and the depolarizing/excitatory to hyperpolarizing/inhibitory GABA shift occurred 4 days later in females than males. Our data support a sex-dependent developmental shift of GABA conductance and chloride gradient, leading to different developmental timing in males and females. Because these developmental sequences are altered in ASD, this study further stresses the importance of developmental timing in pathological neurodevelopment.

MMP-7 is a predictive biomarker of disease progression in patients with idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with poor prognosis, which is characterised by destruction of normal lung architecture and excessive deposition of lung extracellular matrix. The heterogeneity of disease progression in patients with IPF poses significant obstacles to patient care and prevents efficient development of novel therapeutic interventions. Blood biomarkers, reflecting pathobiological processes in the lung, could provide objective evidence of the underlying disease. Longitudinally collected serum samples from the Bosentan Use in Interstitial Lung Disease (BUILD)-3 trial were used to measure four biomarkers (metalloproteinase-7 (MMP-7), Fas death receptor ligand, osteopontin and procollagen type I C-peptide), to assess their potential prognostic capabilities and to follow changes during disease progression in patients with IPF. In baseline BUILD-3 samples, only MMP-7 showed clearly elevated protein levels compared with samples from healthy controls, and further investigations demonstrated that MMP-7 levels also increased over time. Baseline levels of MMP-7 were able to predict patients who had higher risk of worsening and, notably, baseline levels of MMP-7 could predict changes in FVC as early as month 4. MMP-7 shows potential to be a reliable predictor of lung function decline and disease progression.

Long-Term Effect of Endothelin Receptor Antagonism With Bosentan on the Morbidity and Mortality of Patients With Severe Chronic Heart Failure: Primary Results of the ENABLE Trials.

OBJECTIVES: The objective of this clinical trial was to evaluate the long-term effect of endothelin receptor antagonism with bosentan on the morbidity and mortality of patients with severe chronic heart failure. BACKGROUND: Endothelin may play a role in heart failure, but short-term clinical trials with endothelin receptor antagonists have reported disappointing results. Long-term trials are lacking. METHODS: In 2 identical double-blind trials, we randomly assigned 1,613 patients with New York Heart Association functional class IIIb to IV heart failure and an ejection fraction <35% to receive placebo or bosentan (target dose 125 mg twice daily) for a median of 1.5 years. The primary outcome for each trial was clinical status at 9 months (assessed by the hierarchical clinical composite); the primary outcome across the 2 trials was death from any cause or hospitalization for heart failure. RESULTS: Bosentan did not influence clinical status at 9 months in either trial (p = 0.928 and p = 0.263). In addition, 321 patients in the placebo group and 312 patients in the bosentan group died or were hospitalized for heart failure (hazard ratio [HR]: 1.01; 95% confidence interval [CI]: 0.86 to 1.18; p = 0.90). The bosentan group experienced fluid retention within the first 2 to 4 weeks, as evidenced by increased peripheral edema, weight gain, decreases in hemoglobin, and an increased risk of hospitalization for heart failure, despite intensification of background diuretics. During follow-up, 173 patients died in the placebo group and 160 patients died in the bosentan group (HR: 0.94; 95% CI: 0.75 to 1.16). About 10% of the bosentan group showed meaningful increases in hepatic transaminases, but none had acute or chronic liver failure. CONCLUSIONS: Bosentan did not improve the clinical course or natural history of patients with severe chronic heart failure and but caused early and important fluid retention.

Structure of amorphous GeSe9 by neutron diffraction and first-principles molecular dynamics: Impact of trajectory sampling and size effects.

The structure of glassy GeSe9 was investigated by combining neutron diffraction with density-functional-theory-based first-principles molecular dynamics. In the simulations, three different models of N = 260 atoms were prepared by sampling three independent temporal trajectories, and the glass structures were found to be substantially different from those obtained for models in which smaller numbers of atoms or more rapid quench rates were employed. In particular, the overall network structure is based on Sen chains that are cross-linked by Ge(Se4)1/2 tetrahedra, where the latter are predominantly corner as opposed to edge sharing. The occurrence of a substantial proportion of Ge-Se-Se connections does not support a model in which the material is phase separated into Se-rich and GeSe2-rich domains. The appearance of a first-sharp diffraction peak in the Bhatia-Thornton concentration-concentration partial structure factor does, however, indicate a non-uniform distribution of the Ge-centered structural motifs on an intermediate length scale.

Probing the functional impact of sub-retinal prosthesis.

Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). We established a precise V1 mapping as a functional benchmark to demonstrate that sub-retinal implants activate V1 at the appropriate position, scalable to a wide range of visual luminance, but with an aspect-ratio and an extent much larger than expected. Such distorted activation profile can be accounted for by the existence of two sources of diffusion, passive diffusion and activation of ganglion cells' axons en passant. Reverse-engineered electrical pulses based on impedance spectroscopy is the only solution we tested that decreases the extent and aspect-ratio, providing a promising solution for clinical applications.

Soluble surfactant spreading: How the amphiphilicity sets the Marangoni hydrodynamics.

Amphiphiles are molecules combining hydrophilic and hydrophobic parts. The way they arrange in bulk and at interfaces is related to the balance between these two parts, and can be quantified by introducing the critical micellar concentration (cmc). Amphiphiles (also named "surfactants") are also at the origin of dynamical effects: local gradients of interfacial concentrations create the so-called Marangoni flows. Here we study the coupling between the molecule amphiphilicity and these Marangoni flows. We investigate in detail a spreading configuration, where a local excess of surfactants is locally sustained, and follow how these surfactants spread at the interface and diffuse in bulk. We have measured the features of this flow (maximal distance and maximal speed), for different types of surfactant, and as a function of all experimentally available parameters, as well as for two different configurations. In parallel, we propose a detailed hydrodynamical model. For all the measured quantities, we have found a good agreement between the data and the model, evidencing that we have captured the key mechanisms under these spreading experiments. In particular, the cmc turns out to be-as for the static picture of a surfactant-a key element even under dynamical conditions, allowing us to connect the molecule amphiphilicity to its ability to create Marangoni flows.