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Study Question: Are SARS-CoV-2 canonical cell entry machinery, consisting of ACE2, TMPRSS2, NRP1 and LY6E, or alternative potential cell entry machinery, consisting of BSG, ANPEP, CD209, CLEC4G, TMPRSS4, TMPRSS11A, FURIN, CTSB, CTSL and IFITM1, expressed in the human endometrium across the menstrual cycle?Summary Answer: Analysis of cell entry factors for SARS-CoV-2 by single-cell RNA-sequencing (scRNAseq) in the preconceptional human endometrium reveals low risk of infection.What Is Known Already: Gene expression datasets from bulk endometrial tissue show no significant expression of the SARS-CoV-2 receptor ACE2 and TMPRSS2. This is in contrast to reported expression of ACE2 at the single-cell level in the decidua and trophoblast cells at the maternal-fetal interface in early pregnancy, as well as vertical transmission of SARS-CoV-2 during pregnancy.Study Design, Size, Duration: This analysis of SARS-CoV-2 cell entry machinery gene expression was conducted by scRNAseq in 73,181 human endometrial cells isolated from endometrial biopsies obtained from 27 donors across the menstrual cycle.Participants/materials, Setting, Methods: ScRNAseq examined the expression of genes encoding cell entry machinery for SARS-CoV-2. The raw data were from a previously published dataset.Main Results and the Role Of Chance: ScRNAseq analysis showed no significant expression of ACE2 in stromal or unciliated epithelial cells in any phase of the menstrual cycle. TMPRSS2 was expressed in epithelial cells during the early proliferative and mid-secretory phases. Interestingly, expression of NRP1 was observed in both stromal and epithelial cells across all phases of the menstrual cycle, and LY6E was highly expressed in stromal cells. In the mid-secretory phase, coexpression of ACE2 and TMPRSS2 was detected in 0.07% of luminal epithelial cells. No cells simultaneously expressed ACE2, NRP1 and TMPRSS2 at the time of embryo implantation. Focusing on non-canonical cell entry machinery, BSG was highly expressed in all cell types across the menstrual cycle and may interact with CTSB or CTSL proteases, but viral infection using this machinery has not yet been confirmed.Large Scale Data: All raw data in this study can be found at NCBI's Gene Expression Omnibus (series accession code GSE111976) and Sequence Read Archive (accession code SRP135922).Limitations, Reasons For Caution: Our findings at the single-cell level imply low efficiency of SARS-CoV-2 endometrial infection using canonical receptors in a cohort of healthy reproductive-age women; however, infection of endometrial cells can only be assessed in the presence of the virus. All samples were processed for scRNAseq, so no samples are remaining to analyse protein expression or spatial transcriptomics.Wider Implications Of the Findings: Our results offer a useful resource to guide reproductive decisions when assessing risk of endometrial infection by SARS-CoV-2 during the preconceptional period in asymptomatic COVID-19 carriers.Study Funding/competing Interest(s): This study was jointly supported by the March of Dimes, Chan Zuckerberg Biohub and MINECO/FEDER (SAF- 2015-67164-R, to C.S.) (Spanish Government), and the European Union's Horizon 2020 Framework Programme for Research and Innovation (grant agreement 874867). W.W. was supported by the Stanford Bio-X Graduate Bowes Fellowship and Chan Zuckerberg Biohub. F.V. was supported by the Miguel Servet Program Type II of ISCIII (CPII18/00020) and the FIS project (PI18/00957). A patent disclosure has been filed for the study with the title "Methods for assessing endometrial transformation" and the global patent number "EP 3807648 A2" under the inventors S.R.Q., C.S., W.W. and F.V. C.S. is Founder and Head of the Scientific Advisory Board of Igenomix SL. S.R.Q is Director of Mirvie. I.M. is partially employed by Igenomix SL. B.R. has no interests to declare. [ABSTRACT FROM AUTHOR]

Spatiotemporal pattern formation occurs in a variety of nonequilibrium physical and chemical systems. Here we show that a microfluidic device designed to produce reverse micelles can generate complex, ordered patterns as it is continuously operated far from thermodynamic equilibrium. Flow in a microfluidic system is usually simple-viscous effects dominate and the low Reynolds number leads to laminar flow. Self-assembly of the vesicles into patterns depends on channel geometry and relative fluid pressures, enabling the production of motifs ranging from monodisperse droplets to helices and ribbons.

Soft materials are finding applications in areas ranging from microfluidic device technology to nanofabrication. We review recent work in these areas, discuss the motivation for device fabrication with soft materials, and describe applications of soft materials. In particular, we discuss active microfluidic devices for cell sorting and biochemical assays, replication-molded optics with subdiffraction limit features, and nanometer-scale resonators and wires formed from single-molecule DNA templates as examples of how the special properties of soft materials address outstanding problems in device fabrication.

We studied the thermal fluctuations of single DNA molecules with a novel optical tweezer based force spectroscopy technique. This technique combines femtonewton sensitivity with millisecond time resolution, surpassing the sensitivity of previous force measurements in aqueous solution with comparable bandwidth by a hundredfold. Our data resolve long-standing questions concerning internal hydrodynamics of the polymer and anisotropy in the molecular relaxation times and friction coefficients. The dynamics at high extension show interesting nonlinear behavior.

Soft lithography is an alternative to silicon-based micromachining that uses replica molding of nontraditional elastomeric materials to fabricate stamps and microfluidic channels. We describe here an extension to the soft lithography paradigm, multilayer soft lithography, with which devices consisting of multiple layers may be fabricated from soft materials. We used this technique to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer. The softness of these materials allows the device areas to be reduced by more than two orders of magnitude compared with silicon-based devices. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained.

We demonstrate that it is possible to observe single fluorescent molecules using a standard fluorescence microscope with mercury lamp excitation and an inexpensive cooled charge-coupled device (CCD) camera. With this equipment, we have been able to observe single molecules of tetramethyl-rhodamine, rhodamine 6G, fluorescein isothiocyanate and green fluorescent protein. Immobilized molecules were observed both in air and in aqueous solution.

We have demonstrated a disposable microfabricated fluorescence-activated cell sorter (microFACS) for sorting various biological entities. Compared with conventional FACS machines, the microFACS provides higher sensitivity, no cross-contamination, and lower cost. We have used microFACS chips to obtain substantial enrichment of micron-sized fluorescent bead populations of differing colors. Furthermore, we have separated Escherichia coli cells expressing green fluorescent protein from a background of nonfluorescent E. coli cells and shown that the bacteria are viable after extraction from the sorting device. These sorters can function as stand-alone devices or as components of an integrated microanalytical chip.

The behaviour of an isolated polymer floating in a solvent forms the basis of our understanding of polymer dynamics. Classical theories describe the motion of a polymer with linear equations of motion, which yield a set of 'normal modes', analogous to the fundamental frequency and the harmonics of a vibrating violin string. But hydrodynamic interactions make polymer dynamics inherently nonlinear, and the linearizing approximations required for the normal-mode picture have therefore been questioned. Here we test the normal-mode theory by measuring the fluctuations of single molecules of DNA held in a partially extended state with optical tweezers. We find that the motion of the DNA can be described by linearly independent normal modes, and we have experimentally determined the eigenstates of the system. Furthermore, we show that the spectrum of relaxation times obeys a power law.

Single molecules of DNA, visualized in video fluorescence microscopy, were stretched to full extension in a flow, and their relaxation was measured when the flow stopped. The molecules, attached by one end to a 1-micrometer bead, were manipulated in an aqueous solution with optical tweezers. Inverse Laplace transformations of the relaxation data yielded spectra of decaying exponentials with distinct peaks, and the longest time component (tau) increased with length (L) as tau approximately L 1.68 +/- 0.10. A rescaling analysis showed that most of the relaxation curves had a universal shape and their characteristic times (lambda t) increased as lambda t approximately L 1.65 +/- 0.13. These results are in qualitative agreement with the theoretical prediction of dynamical scaling.