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Droplet microfluidics has become a powerful tool in precision medicine, green biotechnology, and cell therapy for single-cell analysis and selection by virtue of its ability to effectively confine cells. However, there remains a fundamental trade-off between droplet volume and sorting throughput, limiting the advantages of droplet microfluidics to small droplets (

Introduction: Women play an essential role in health care delivery, and it is vital that they have equal representation in health leadership for equity, innovation, and the strengthening of health systems globally. Yet women remain vastly underrepresented in global health leadership positions, providing a clear example of the deeply rooted power imbalances that are central to the calls to decolonize global health. We conducted a multi-country study in Haiti, Tanzania, India, and the USA to examine gender-based challenges to career advancement for women in the global health workforce. Quantitative data on the type and prevalence of gender-based challenges has been previously reported. In this study, we analyze qualitative data collected through focus group discussions and in-depth interviews to understand women's experiences of gender-based obstacles to career advancement, their perceptions of underlying drivers, and perspectives on effective solutions. Guided by an adaptation of the Social Action Theory, we conducted focus group discussions and in-depth interviews with women at 4 major academic centers for clinical care and research in Haiti, India, Tanzania, and the United States. In total, 85 women participated in focus groups and 15 also participated in in-depth interviews. Discussions and interviews were conducted in the local language, by an experienced local facilitator unaffiliated with the participating institution, between 2017 and 2018. Discussions were recorded, transcribed, and translated. Data were analyzed by interpretive phenomenological methods for emergent themes. Three transcendent themes on gender-based challenges were identified: 1) cultural power imbalance, referring to the prevailing norms and engrained assumptions that women are less capable than men and that women's primary responsibility should be to their families; 2) institutional power imbalance, referring to the systematic gender bias upheld by existing leadership and power structures, and ranging from exclusion from career development opportunities to sexual harassment and assault; and 3) restricted agency, referring to women's limited ability to change their circumstances because of unequal cultural and institutional structures. Participants also described local, actionable solutions to address these barriers. These included: 1) formal reporting systems for sexual harassment and assault; 2) peer support and mentorship; and 3) accessible leadership training and mandatory gender equity training. Participants proposed feasible strategies to address gender-based challenges that could improve women's retention in health careers and foster their rise to leadership. Increasing the representation of women in global health leadership positions responds directly to efforts to decolonize global health and is integral to strengthening health systems and improving health outcomes for women and children worldwide., Competing Interests: The authors declare that no competing interests exist., (Copyright: © 2023 Riche et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Two-Photon Microscopy has become an invaluable tool for biological and medical research, providing high sensitivity, molecular specificity, inherent three-dimensional sub-cellular resolution and deep tissue penetration. In terms of imaging speeds, however, mechanical scanners still limit the acquisition rates to typically 10-100 frames per second. Here we present a high-speed non-linear microscope achieving kilohertz frame rates by employing pulse-modulated, rapidly wavelength-swept lasers and inertia-free beam steering through angular dispersion. In combination with a high bandwidth, single-photon sensitive detector, this enables recording of fluorescent lifetimes at speeds of 88 million pixels per second. We show high resolution, multi-modal - two-photon fluorescence and fluorescence lifetime (FLIM) - microscopy and imaging flow cytometry with a digitally reconfigurable laser, imaging system and data acquisition system. These high speeds should enable high-speed and high-throughput image-assisted cell sorting.

Nucleic acid amplification assays including loop-mediated isothermal amplification (LAMP) are routinely used in diagnosing diseases and monitoring water and food quality. The results of amplification in these assays are commonly measured with an analog fluorescence readout, which requires specialized optical equipment and can lack quantitative precision. Digital analysis of amplification in small fluid compartments based on exceeding a threshold fluorescence level can enhance the quantitative precision of nucleic acid assays (i.e., digital nucleic acid amplification assays), but still requires specialized optical systems for fluorescence readout and the inclusion of a fluorescent dye. Here, we report Fractal LAMP, an automated method to detect amplified DNA in subnanoliter scale droplets following LAMP in a label-free manner. Our computer vision algorithm achieves high accuracy detecting DNA amplification in droplets by identifying LAMP byproducts that form fractal structures observable in brightfield microscopy. The capabilities of Fractal LAMP are further realized by developing a Bayesian model to estimate DNA concentrations for unknown samples and a bootstrapping method to estimate the number of droplets required to achieve target limits of detection. This digital, label-free assay has the potential to lower reagent and reader cost for nucleic acid measurement while maintaining high quantitative accuracy over 3 orders of magnitude of concentration.

Microalgae are an attractive feedstock organism for sustainable production of biofuels, chemicals, and biomaterials, but the ability to rationally engineer microalgae to enhance production has been limited. To enable the evolution-based selection of new hyperproducing variants of microalgae, a method is developed that combines phase-transitioning monodisperse gelatin hydrogel droplets with commercial flow cytometric instruments for high-throughput screening and selection of clonal populations of cells with desirable properties, such as high lipid productivity per time traced over multiple cell cycles. It is found that gelatin microgels enable i) the growth and metabolite (e.g., chlorophyll and lipids) production of single microalgal cells within the compartments, ii) infusion of fluorescent reporter molecules into the hydrogel matrices following a sol-gel transition, iii) selection of high-producing clonal populations of cells using flow cytometry, and iv) cell recovery under mild conditions, enabling regrowth after sorting. This user-friendly method is easily integratable into directed cellular evolution pipelines for strain improvement and can be adopted for other applications that require high-throughput processing, e.g., cellular secretion phenotypes and intercellular interactions., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Microalgal biofuels and biomass have ecofriendly advantages as feedstocks. Improved understanding and utilization of microalgae require large-scale analysis of the morphological and metabolic heterogeneity within populations. Here, with Euglena gracilis as a model microalgal species, we evaluate how fluorescence- and brightfield-derived-image-based descriptors vary during environmental stress at the single-cell level. This is achieved with a new multiparameter fluorescence-imaging cytometric technique that allows the assaying of thousands of cells per experiment. We track morphological changes, including the intensity and distribution of intracellular lipid droplets, and pigment autofluorescence. The combined fluorescence-morphological analysis identifies new metrics not accessible with traditional flow cytometry, including the lipid-to-cell-area ratio (LCAR), which shows promise as an indicator of oil productivity per biomass. Single-cell metrics of lipid productivity were highly correlated ( R 2 > 0.90, p < 0.005) with bulk oil extraction. Such chemomorphological atlases of algal species can help optimize growth conditions and selection approaches for large-scale biomass production.

G protein-coupled receptor (GPCR) is incorporated into polymeric vesicles made up of diblock copolymer bilayers. Successfully incorporated GPCRs exhibit correct biased physiological orientation and respond to various ligands. After extended dehydrated storage via lyophilization and subsequent rehydration, diblock copolymer polymersomes retain their shape and incorporated GPCR retains its function., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The translation of batch chemistries onto continuous flow platforms requires addressing the issues of consistent fluidic behaviour, channel fouling and high-throughput processing. Droplet microfluidic technologies reduce channel fouling and provide an improved level of control over heat and mass transfer to control reaction kinetics. However, in conventional geometries, the droplet size is sensitive to changes in flow rates. Here we report a three-dimensional droplet generating device that exhibits flow invariant behaviour and is robust to fluctuations in flow rate. In addition, the droplet generator is capable of producing droplet volumes spanning four orders of magnitude. We apply this device in a parallel network to synthesize platinum nanoparticles using an ionic liquid solvent, demonstrate reproducible synthesis after recycling the ionic liquid, and double the reaction yield compared with an analogous batch synthesis.

We have studied the dynamics of Lissamine Rhodamine B dye sensitization-induced oxidation of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs), where the progression of the underlying chemical processes was followed via vesicle membrane area changes. The surface-area-to-volume ratio of our spherical GUVs increased after as little as ten seconds of irradiation. The membrane area expansion was coupled with high amplitude fluctuations not typical of GUVs in isoosmotic conditions. To accurately measure the area of deformed and fluctuating membranes, we utilized a dual-beam optical trap (DBOT) to stretch GUV membranes into a geometrically regular shape. Further oxidation led to vesicle contraction, and the GUVs became tense, with micron-scale pores forming in the bilayer. We analyzed the GUV morphological behaviors as two consecutive rate-limiting steps. We also considered the effects of altering DOPC and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (RhDPPE) concentrations. The resulting kinetic model allows us to measure how lipid molecular area changes during oxidation, as well as to determine the rate constants controlling how quickly oxidation products are formed. Controlled membrane oxidation leading to permeabilization is also a potential tool for drug delivery based on engineered photosensitizer-containing lipid vesicles., (Copyright © 2014 Elsevier B.V. All rights reserved.)

We have demonstrated the application of low surface energy fluoropolymer coatings onto poly(dimethylsiloxane) (PDMS) microfluidic devices for droplet formation and extraction-induced merger of droplets. Initiated chemical vapor deposition (iCVD) was used to pattern fluoropolymer coatings within microchannels based on geometrical constraints. In a two-phase flow system, the range of accessible flow rates for droplet formation was greatly enhanced in the coated devices. The ability to controllably apply the coating only at the inlet facilitated a method for merging droplets. An organic spacer droplet was extracted from between a pair of aqueous droplets. The size of the organic droplet and the flow rate controlled the time to merge the aqueous droplets; the process of merging was independent of the droplet sizes. Extraction-induced droplet merging is a robust method for manipulating droplets that could be applied in translating multi-step reactions to microfluidic platforms.

We have employed a simple modular approach to install small chalcogenol ligands on the surface of CdSe nanocrystals. This versatile modification strategy provides access to thiol, selenol, and tellurol ligand sets via the in situ reduction of R2E2 (R=tBu, Bn, Ph; E=S, Se, Te) by diphenylphosphine (Ph2PH). The ligand exchange chemistry was analyzed by solution NMR spectroscopy, which reveals that reduction of the R2E2 precursors by Ph2PH directly yields active chalcogenol ligands that subsequently bind to the surface of the CdSe nanocrystals. Thermogravimetric analysis, FT-IR spectroscopy, and energy dispersive X-ray spectroscopy provide further evidence for chalcogenol addition to the CdSe surface with a concomitant reduction in overall organic content from the displacement of native ligands. Time-resolved and low temperature photoluminescence measurements showed that all of the phenylchalcogenol ligands rapidly quench the photoluminescence by hole localization onto the ligand. Selenol and tellurol ligands exhibit a larger driving force for hole transfer than thiol ligands and therefore quench the photoluminescence more efficiently. The hole transfer process could lead to engineering long-lived, partially separated excited states.

Cholera, previously unrecognized in Haiti, spread through the country in the fall of 2010. An analysis was performed to understand the epidemiological characteristics, clinical management, and risk factors for disease severity in a population seen at the GHESKIO Cholera Treatment Center in Port-au-Prince. A comprehensive review of the medical records of patients admitted during the period of October 28, 2010-July 10, 2011 was conducted. Disease severity on admission was directly correlated with older age, more prolonged length of stay, and presentation during the two epidemic waves seen in the observation period. Although there was a high seroprevalence of human immunodeficiency virus (HIV), severity of cholera was not greater with HIV infection. This study documents the correlation of cholera waves with rainfall and its reduction in settings with improved sanitary conditions and potable water when newly introduced cholera affects all ages equally so that interventions must be directed throughout the population.

We present a simple solution casting technique to apply polymer welds to stabilize capillary-force directed self-assembled systems including arrays of pillars and microbeads. The strength of the polymer welds can be enhanced by increasing either the polymer concentration or molecular weight. The use of responsive polymers to form the welds allow for the fabrication of hierarchical structures that actuate in response to external stimuli. For example, temperature-responsive and pH-responsive microstructures can be formed by solution casting poly(vinyl methyl ether) and poly(methacrylic acid), respectively. We demonstrate that polymer welds formed using biocompatible alginate allows for controllable release of microbeads in microfluidic channels, which has potential applications in drug delivery.

Imidazolium-based ionic liquids have been widely utilized as versatile solvents for metal nanoparticle synthesis; however, reactions to synthesize silver nanoparticles that are performed identically in different commercially obtained lots of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF(4)) give divergent results. This suggests that impurities in these nominally identical solvents play an important role in the resulting silver nanoparticle quality. To test the effect that impurities have on the quality of silver nanoparticles synthesized in BMIM-BF(4), silver nanoparticles were synthesized in carefully prepared and purified BMIM-BF(4) and compared against silver nanoparticles that were synthesized in the purified BMIM-BF(4) that had been spiked with trace amounts of water, chloride, and 1-methylimidazole. It was clearly demonstrated that trace amounts of these common ionic liquid impurities cause significant deviation in size and shape (creating polydisperse and irregularly shaped ensembles of both large and small particles), and also negatively impact the stabilization of the resulting silver nanoparticles.

Droplet-based microfluidic platforms have the potential to provide superior control over mixing as compared to traditional batch reactions. Ionic liquids have advantageous properties for metal nanoparticle synthesis as a result of their low interfacial tension and complexing ability; however, droplet formation of ionic liquids within microfluidic channels in a two-phase system has not yet been attained because of their complex interfacial properties and high viscosities. Here, breakup of an imidazolium-based ionic liquid into droplets in a simple two-phase system has for the first time been achieved and characterized by using a microchannel modified with a thin film fluoropolymer. This microfluidic/ionic liquid droplet system was used to produce small, spherical gold (4.28 ± 0.84 nm) and silver (3.73 ± 0.77 nm) nanoparticles.

The interior surfaces of pre-assembled poly(dimethylsiloxane) (PDMS) microfluidic devices were modified with a cross-linked fluoropolymer barrier coating that significantly increased the chemical compatibility of the devices., (This journal is © The Royal Society of Chemistry 2011)