Thin adhesive oil films lead to anomalously stable mixtures of water in oil.

Oil and water can only be mixed by dispersing droplets of one fluid in the other. When two droplets approach one another, the thin film that separates them invariably becomes unstable, causing the droplets to coalesce. The only known way to avoid this instability is through addition of a third component, typically a surfactant, which stabilizes the thin film at its equilibrium thickness. We report the observation that a thin fluid film of oil separating two water droplets can lead to an adhesive interaction between the droplets. Moreover, this interaction prevents their coalescence over timescales of several weeks, without the use of any surfactant or solvent.

Long-term Outcomes of Tibial Spine Avulsion Fractures After Open Reduction With Osteosuturing Versus Arthroscopic Screw Fixation: A Multicenter Comparative Study.

Background: More information is needed regarding return to preinjury sport levels and patient-reported outcomes after tibial spine avulsion (TSA) fracture, which is most common in children aged 8 to 12 years. Purpose: To analyze return to play/sport (RTP), subjective knee-specific recovery, and quality of life in patients after TSA fracture treated with open reduction with osteosuturing versus arthroscopic reduction with internal screw fixation. Study Design: Cohort study; Level of evidence, 3. Methods: This study included 61 patients <16 years old with TSA fracture treated via open reduction with osteosuturing (n = 32) or arthroscopic reduction with screw fixation (n = 29) at 4 institutions between 2000 and 2018; all patients had at least 24 months of follow-up (mean ± SD, 87.0 ± 47.1 months; range, 24-189 months). The patients completed questionnaires regarding ability to return to preinjury-level sports, subjective knee-specific recovery, and health-related quality of life, and results were compared between treatment groups. Univariate and multivariate logistic regression analyses were conducted to determine variables associated with failure to return to preinjury level of sport. Results: The mean patient age was 11 years, with a slight male predominance (57%). Open reduction with osteosuturing was associated with a quicker RTP time than arthroscopy with screw implantation (median, 8.0 vs 21.0 weeks; P < .001). Open reduction with osteosuturing was also associated with a lower risk of failure to RTP at preinjury level (adjusted odds ratio, 6.4; 95% CI, 1.1-36.0; P = .035). Postoperative displacement >3 mm increased the risk of failure to RTP at preinjury level regardless of treatment group (adjusted odds ratio, 15.2; 95% CI, 1.2-194.9; P = .037). There was no difference in knee-specific recovery or quality of life between the treatment groups. Conclusion: Open surgery with osteosuturing was a more viable option for treating TSA fractures because it resulted in a quicker RTP time and a lower rate of failure to RTP as compared with arthroscopic screw fixation. Precise reduction contributed to improved RTP.

Management of anterior cruciate ligament tears in Tanner stage 1 and 2 children: a narrative review and treatment algorithm guided by ACL tear location.

The incidence of anterior cruciate ligament (ACL) tears in skeletally immature patients has acutely increased over the last 20 years, yet there is no consensus on a single "best treatment." Selection of an optimal treatment is critical and based on individual circumstances; consequently, we propose a treatment-selection algorithm based on skeletal development, ACL tear location, type, and quality, as well as parental perspective in order to facilitate the decision-making process. We combined our surgical group's extensive case histories of ACL tear management in Tanner Stage 1 and 2 patients with those in the literature to form a consolidated data base. For each case the diagnostic phase, communication with patient and parents, treatment choice(s), selected surgical techniques and rehabilitation schedule were critically analyzed and compared for patient outcomes. MRI-imaging and intraoperative tissue quality assessment were preeminent in importance for selection of the optimal treatment strategy. Considerations for selecting an optimal treatment included: associated lesions, the child/patient and parent(s)' well-informed and counseled consent, biological potential, and the potential for successful ACL preservative surgery. Complete ACL tears were evaluated according to tear-location. In type I and II ACL tears with remaining good tissue quality, we propose primary ACL repair. In type III and IV ACL tears we propose physeal-sparing reconstruction with an iliotibial band graft. Finally, in the case of a type V ACL tear, we propose that the best treatment be based on the Meyers-McKeever classification. We present a facile decision-making algorithm for ACL management in pediatric patients based on specific elements of tissue damage and status.

Isolated MPFL reconstruction with soft tissue femoral fixation technique in 54 skeletally immature patients: Clinical outcomes at 2 years follow-up. A French multicenter retrospective study.

BACKGROUND: Medial patello-femoral ligament (MPFL) reconstruction is one of the therapeutic options to treat patellofemoral instability. Classically, a à la carte treatment of skeletal and ligament abnormalities is described. This option is difficult to achieve in children because bony procedures can damage the femoral and/or tibial growth plate. The objective was to evaluate a strategy for isolated reconstruction of the MPFL in the treatment of objective patellar instabilities in children, in a large cohort. The return to sport, knee function and pain or discomfort were studied as secondary endpoints. METHODS: This French multicenter retrospective study included 54 pediatric patients with objective patellofemoral instability. Patients were included if they had presented at least 2 episodes of objective patella dislocation. A Deie-like technique with gracilis tendon graft, soft tissue femoral fixation and patellar bone tunnels for patellar fixation was used. Recurrence of dislocation was studied as the primary endpoint, and the recurrence rate was compared with the literature. A comparison of functional scores (Kujala, Lille femoro-patellar instability score or LFPI Score and Tegner activity score) and NRS between pre- and postoperative was studied as a secondary objective. RESULTS: A recurrence of femoro-patellar instability was observed for five patients within 2 years follow up (9%). A significant improvement of the Kujala, LFPI score, Tegner and NRS scores was observed (p<0.001). CONCLUSION: Isolated reconstruction of the MPFL presents a risk of recurrence of 9% at 2years follow-up. This technique significantly improves the functional scores of the knee. This modified Deie technique provides good clinical and functional results, allowing return to sports with an acceptable risk of recurrence of patellar dislocation, similar to those observed in the literature. Isolated MPFL reconstruction as a first-line treatment appears to be a reliable and effective technique in terms of recurrence of dislocation and functional scores. It allows early recovery and rehabilitation and has lower morbidity than procedures requiring bone gestures. LEVEL OF EVIDENCE: III, retrospective comparative study.

Discovery and characterization of UipA, a uranium- and iron-binding PepSY protein involved in uranium tolerance by soil bacteria.

Uranium is a naturally occurring radionuclide. Its redistribution, primarily due to human activities, can have adverse effects on human and non-human biota, which poses environmental concerns. The molecular mechanisms of uranium tolerance and the cellular response induced by uranium exposure in bacteria are not yet fully understood. Here, we carried out a comparative analysis of four actinobacterial strains isolated from metal and radionuclide-rich soils that display contrasted uranium tolerance phenotypes. Comparative proteogenomics showed that uranyl exposure affects 39-47% of the total proteins, with an impact on phosphate and iron metabolisms and membrane proteins. This approach highlighted a protein of unknown function, named UipA, that is specific to the uranium-tolerant strains and that had the highest positive fold-change upon uranium exposure. UipA is a single-pass transmembrane protein and its large C-terminal soluble domain displayed a specific, nanomolar binding affinity for UO22+ and Fe3+. ATR-FTIR and XAS-spectroscopy showed that mono and bidentate carboxylate groups of the protein coordinated both metals. The crystal structure of UipA, solved in its apo state and bound to uranium, revealed a tandem of PepSY domains in a swapped dimer, with a negatively charged face where uranium is bound through a set of conserved residues. This work reveals the importance of UipA and its PepSY domains in metal binding and radionuclide tolerance.

3D cell migration in the presence of chemical gradients using microfluidics.

Chemotaxis is an important biological process involved in the development of multicellular organisms, immune response and cancer metastasis. In order to better understand how cells follow chemical cues in their native environments, we recently developed a microfluidics-based chemotaxis device that allows for observation of cells or cell aggregates in 3D networks in response to tunable chemical gradients (Aizel et al., 2017). Here, we describe the methods required for fabrication of this device as well as its use for live imaging experiments and subsequent analysis of imaging data. This device can be adapted to study a number of different cell arrangements and chemical gradients, opening new avenues of research in 3D chemotaxis.

A tuneable microfluidic system for long duration chemotaxis experiments in a 3D collagen matrix.

In many cell types, migration can be oriented towards a chemical stimulus. In mammals, for example, embryonic cells migrate to follow developmental cues, immune cells migrate toward sites of inflammation, and cancer cells migrate away from the primary tumour and toward blood vessels during metastasis. Understanding how cells migrate in 3D environments in response to chemical cues is thus crucial to understanding directed migration in normal and disease states. To date, chemotaxis in mammalian cells has been primarily studied using 2D migration models. However, it is becoming increasingly clear that the mechanisms by which cells migrate in 2D and 3D environments dramatically differ, and cells in their native environments are confronted with a complex chemical milieu. To address these issues, we developed a microfluidic device to monitor the behaviour of cells embedded in a 3D collagen matrix in the presence of complex concentration fields of chemoattractants. This tuneable microsystem enables the generation of (1) homogeneous, stationary gradients set by a purely diffusive mechanism, or (2) spatially evolving, stationary gradients, set by a convection-diffusion mechanism. The device allows for stable gradients over several days and is large enough to study the behaviour of large cell aggregates. We observe that primary mature dendritic cells respond uniformly to homogeneous diffusion gradients, while cell behaviour is highly position-dependent in spatially variable convection-diffusion gradients. In addition, we demonstrate a directed response of cancer cells migrating away from tumour-like aggregates in the presence of soluble chemokine gradients. Together, this microfluidic device is a powerful system to observe the response of different cells and aggregates to tuneable chemical gradients.

Controlled production of sub-millimeter liquid core hydrogel capsules for parallelized 3D cell culture.

Liquid core capsules having a hydrogel membrane are becoming a versatile tool for three-dimensional culture of micro-organisms and mammalian cells. Making sub-millimeter capsules at a high rate, via the breakup of a compound jet in air, opens the way to high-throughput screening applications. However, control of the capsule size monodispersity, especially required for quantitative bioassays, was still lacking. Here, we report how the understanding of the underlying hydrodynamic instabilities that occur during the process can lead to calibrated core-shell bioreactors. The requirements are: i) damping the shear layer instability that develops inside the injector arising from the co-annular flow configuration of liquid phases having contrasting viscoelastic properties; ii) controlling the capillary instability of the compound jet by superposing a harmonic perturbation onto the shell flow; iii) avoiding coalescence of drops during jet fragmentation as well as during drop flight towards the gelling bath; iv) ensuring proper engulfment of the compound drops into the gelling bath for building a closed hydrogel shell. We end up with the creation of numerous identical compartments in which cells are able to form multicellular aggregates, namely spheroids. In addition, we implement an intermediate composite hydrogel layer, composed of alginate and collagen, allowing cell adhesion and thus the formation of epithelia or monolayers of cells.

Cellular capsules as a tool for multicellular spheroid production and for investigating the mechanics of tumor progression in vitro.

Deciphering the multifactorial determinants of tumor progression requires standardized high-throughput preparation of 3D in vitro cellular assays. We present a simple microfluidic method based on the encapsulation and growth of cells inside permeable, elastic, hollow microspheres. We show that this approach enables mass production of size-controlled multicellular spheroids. Due to their geometry and elasticity, these microcapsules can uniquely serve as quantitative mechanical sensors to measure the pressure exerted by the expanding spheroid. By monitoring the growth of individual encapsulated spheroids after confluence, we dissect the dynamics of pressure buildup toward a steady-state value, consistent with the concept of homeostatic pressure. In turn, these confining conditions are observed to increase the cellular density and affect the cellular organization of the spheroid. Postconfluent spheroids exhibit a necrotic core cemented by a blend of extracellular material and surrounded by a rim of proliferating hypermotile cells. By performing invasion assays in a collagen matrix, we report that peripheral cells readily escape preconfined spheroids and cell-cell cohesivity is maintained for freely growing spheroids, suggesting that mechanical cues from the surrounding microenvironment may trigger cell invasion from a growing tumor. Overall, our technology offers a unique avenue to produce in vitro cell-based assays useful for developing new anticancer therapies and to investigate the interplay between mechanics and growth in tumor evolution.

An improved method for specific and quantitative determination of the clopidogrel active metabolite isomers in human plasma.

Pharmacokinetic analyses of clopidogrel are hampered by the existence of multiple active metabolite isomers (H1 to H4) and their instability in blood. We sought to retest the pharmacodynamic activities of the four individual active metabolite isomers in vitro, with the ultimate aim of determining the isomers responsible for clopidogrel activity in vivo. In vitro activity was evaluated by measuring binding of [³³P]-2-methylthio-ADP on P2Y12-expressing Chinese hamster ovary (CHO) cells and human platelets in platelet-rich plasma (PRP). A stereoselective method that used reverse-phase ultra high-performance liquid chromatography (UHPLC) and tandem mass spectrometry (MS) was developed to measure individual concentrations of the stable 3'-methoxyacetophenone (MP) derivatives of H1-H4. The new method was used to analyze plasma samples from clopidogrel-treated subjects enrolled in a phase I clinical trial. In vitro binding assays confirmed the previously observed biological activity of H4 (IC50: CHO-P2Y12: 0.12 µM; PRP: 0.97 µM) and inactivity of H3, and demonstrated that H1 was also inactive. Furthermore, H2 demonstrated approximately half of the biological activity in vitro compared with H4. Optimisation of UHPLC conditions and MS collision parameters allowed the resolution and detection of the four derivatised active metabolite isomers (MP-H1 to MP-H4). The stereoselective assay was extensively validated, and was accurate and precise over the concentration range 0.5-250 ng/ml. Only MP-H3 and MP-H4 were quantifiable in incurred clinical samples. Based on in vitro pharmacodynamic data and found concentrations, the active metabolite isomer H4 is the only diastereoisomer of clinical relevance for documenting the pharmacokinetic profile of the active metabolite of clopidogrel.

Structural genomics of the SARS coronavirus: cloning, expression, crystallization and preliminary crystallographic study of the Nsp9 protein.

The aetiologic agent of the recent epidemics of Severe Acute Respiratory Syndrome (SARS) is a positive-stranded RNA virus (SARS-CoV) belonging to the Coronaviridae family and its genome differs substantially from those of other known coronaviruses. SARS-CoV is transmissible mainly by the respiratory route and to date there is no vaccine and no prophylactic or therapeutic treatments against this agent. A SARS-CoV whole-genome approach has been developed aimed at determining the crystal structure of all of its proteins or domains. These studies are expected to greatly facilitate drug design. The genomes of coronaviruses are between 27 and 31.5 kbp in length, the largest of the known RNA viruses, and encode 20-30 mature proteins. The functions of many of these polypeptides, including the Nsp9-Nsp10 replicase-cleavage products, are still unknown. Here, the cloning, Escherichia coli expression, purification and crystallization of the SARS-CoV Nsp9 protein, the first SARS-CoV protein to be crystallized, are reported. Nsp9 crystals diffract to 2.8 A resolution and belong to space group P6(1/5)22, with unit-cell parameters a = b = 89.7, c = 136.7 A. With two molecules in the asymmetric unit, the solvent content is 60% (V(M) = 3.1 A(3) Da(-1)).