Predictable duty cycle modulation through coupled pairing of syringes with microfluidic oscillators

The ability to elicit distinct duty cycles from the same self-regulating microfluidic oscillator device would greatly enhance the versatility of this micro-machine as a tool, capable of recapitulating in vitro the diverse oscillatory processes that occur within natural systems. We report a novel approach to realize this using the coordinated modulation of input volumetric flow rate ratio and fluidic capacitance ratio. The demonstration uses a straightforward experimental system where fluid inflow to the oscillator is provided by two syringes (of symmetric or asymmetric cross-sectional area) mounted upon a single syringe pump applying pressure across both syringes at a constant linear velocity. This produces distinct volumetric outflow rates from each syringe that are proportional to the ratio between their cross-sectional areas. The difference in syringe cross-sectional area also leads to differences in fluidic capacitance; this underappreciated capacitive difference allows us to present a simplified expression to determine the microfluidic oscillators duty cycle as a function of cross-sectional area. Examination of multiple total volumetric inflows under asymmetric inflow rates yielded predictable and robust duty cycles ranging from 50% to 90%. A method for estimating the outflow duration for each inflow under applied flow rate ratios is provided to better facilitate the utilization of this system in experimental protocols requiring specific stimulation and rest intervalsopen1

Antimicrobial Microwebs of DNA–Histone Inspired from Neutrophil Extracellular Traps

Neutrophil extracellular traps (NETs) are decondensed chromatin networks released by neutrophils that can trap and kill pathogens but can also paradoxically promote biofilms. The mechanism of NET functions remains ambiguous, at least in part, due to their complex and variable compositions. To unravel the antimicrobial performance of NETs, a minimalistic NET‐like synthetic structure, termed “microwebs,” is produced by the sonochemical complexation of DNA and histone. The prepared microwebs have structural similarity to NETs at the nanometer to micrometer dimensions but with well‐defined molecular compositions. Microwebs prepared with different DNA to histone ratios show that microwebs trap pathogenic Escherichia coli in a manner similar to NETs when the zeta potential of the microwebs is positive. The DNA nanofiber networks and the bactericidal histone constituting the microwebs inhibit the growth of E. coli. Moreover, microwebs work synergistically with colistin sulfate, a common and a last‐resort antibiotic, by targeting the cell envelope of pathogenic bacteria. The synthesis of microwebs enables mechanistic studies not possible with NETs, and it opens new possibilities for constructing biomimetic bacterial microenvironments to better understand and predict physiological pathogen responses.Microwebs with bacteria trapping and killing functions are designed to mimic neutrophil extracellular traps—an immune defense weapon to fight against invading pathogens. The composition–structure–function relationship of the synthetic structure is discussed, and the collaborative action between microwebs and antibiotics allows better elimination of pathogenic bacteria, Escherichia coli.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149216/1/adma201807436-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149216/2/adma201807436_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149216/3/adma201807436.pd

The Design And Operation Of A Microfluidic Droplet Random Access Memory (dram) Platform

The work completed and reported herein was motivated by a broad vision wherein \u27information\u27, in the form of flow-suspended objects (FSOs) (e.g. individual droplets/emulsions, mammalian cells, isolated nuclei, microbeads, etc), may be handled and manipulated in a manner inspired by both the handling of bits by computational random-access memory and of inventory within a warehouse. Such a system, analogous to a fluidic computer, would resemble a network of interconnected modular components designed to perform operations ranging from sample enrichment (through repeated cycles of ‘trapping’ and ‘release’) and monitoring/incubation (as may be desired for biological samples or compartmentalized chemical reactions), to Boolean operations (e.g. the merging or splitting of droplets). Such a system could then be utilized for performing complex single-unit operations (e.g. single cell genomics/proteomics) without requiring off-chip sample handling (Figure 1) – a true lab on a chip. Contextualized by this broad vision, the work reported herein sought to develop a fluidic memory-analog capable of (1) efficiently capturing FSOs within individual storage units, (2) selectively releasing FSOs from specific storage units without disrupting the contents of other storage units, and (3) achieving these functional objectives in a manner capable of handling at least 10,000 FSOs in an area smaller than 3,750 mm2 (this area constraint is owed to the use of fabrication techniques and equipment that limit the surface area of devices to the surface area of a standard 50 x 75 mm glass slide). These design constraints ultimately resulted in (1) the development of a novel elastomeric valve that could be patterned at densities \u3e 1,000 valves per device, (2) the utilization of this valve within a gas-on-gas multiplexer capable of providing the operational scalability of large-scale integration (LSI), (3) the optimization of a storage unit geometry that is both scalable and capable of efficiently capturing single FSOs, and (4) the integration of these components in the design of a system capable of selectively capturing and releasing single FSOs

Visualization of Nuclease- and Serum-Mediated Chromatin Degradation with DNA–Histone Mesostructures

This study analyzed the nuclease- and serum-driven degradation of millimeter-scale, circular DNA–histone mesostructures (DHMs). DHMs are bioengineered chromatin meshes of defined DNA and histone compositions designed as minimal mimetics of physiological extracellular chromatin structures, such as neutrophil extracellular traps (NETs). Taking advantage of the defined circular shape of the DHMs, an automated time-lapse imaging and image analysis method was developed and used to track DHM degradation and shape changes over time. DHMs were degraded well by 10 U/mL concentrations of deoxyribonuclease I (DNase I) but not by the same level of micrococcal nuclease (MNase), whereas NETs were degraded well by both nucleases. These comparative observations suggest that DHMs have a less accessible chromatin structure compared to NETs. DHMs were degraded by normal human serum, although at a slower rate than NETs. Interestingly, time-lapse images of DHMs revealed qualitative differences in the serum-mediated degradation process compared to that mediated by DNase I. Importantly, despite their reduced susceptibility to degradation and compositional simplicity, the DHMs mimicked NETs in being degraded to a greater extent by normal donor serum compared to serum from a lupus patient with high disease activity. These methods and insights are envisioned to guide the future development and expanded use of DHMs, beyond the previously reported antibacterial and immunostimulatory analyses, to extracellular chromatin-related pathophysiological and diagnostic studies

Visualization of Nuclease- and Serum-Mediated Chromatin Degradation with DNA–Histone Mesostructures

This study analyzed the nuclease- and serum-driven degradation of millimeter-scale, circular DNA–histone mesostructures (DHMs). DHMs are bioengineered chromatin meshes of defined DNA and histone compositions designed as minimal mimetics of physiological extracellular chromatin structures, such as neutrophil extracellular traps (NETs). Taking advantage of the defined circular shape of the DHMs, an automated time-lapse imaging and image analysis method was developed and used to track DHM degradation and shape changes over time. DHMs were degraded well by 10 U/mL concentrations of deoxyribonuclease I (DNase I) but not by the same level of micrococcal nuclease (MNase), whereas NETs were degraded well by both nucleases. These comparative observations suggest that DHMs have a less accessible chromatin structure compared to NETs. DHMs were degraded by normal human serum, although at a slower rate than NETs. Interestingly, time-lapse images of DHMs revealed qualitative differences in the serum-mediated degradation process compared to that mediated by DNase I. Importantly, despite their reduced susceptibility to degradation and compositional simplicity, the DHMs mimicked NETs in being degraded to a greater extent by normal donor serum compared to serum from a lupus patient with high disease activity. These methods and insights are envisioned to guide the future development and expanded use of DHMs, beyond the previously reported antibacterial and immunostimulatory analyses, to extracellular chromatin-related pathophysiological and diagnostic studies

Nanoparticle Assemblies into Luminescent Dendrites in Shrinking Microdroplets

The self-assembly of nanoparticles (NPs) is essential for emerging dispersion-based energy-conscious technologies. Of particular interest are micro- and macro-scale self-organizing superstructures that can bridge 2D/3D processing scales. Here we report the spontaneous assembly of CdTe NPs within an aqueous microdroplet suspended in soybean oil. The gradual diffusion of the water into the surrounding medium results in shrinking of the microdroplet, and a concomitant formation of branched assemblies from CdTe NPs that evolve in size from ∼50 μm to ∼1000 μm. The fractal dimension of NP assemblies increases from ∼1.7 to ∼1.9 during the assembly process. We found that constituents of the soybean oil enter the aqueous solution across the microdroplet interface and affect NP assembly. The obtained NP dendrites can be further altered morphologically by illumination with light that results in the disassembly of the NP dendrites. The use of this microheterogeneous dispersion platform with partially soluble hydrophilic and hydrophobic solvents highlights the sensitivity of the NP assembly process to environment and presents an opportunity to explore droplet-confined NP assembly

Nanoparticle Assemblies into Luminescent Dendrites in Shrinking Microdroplets

The self-assembly of nanoparticles (NPs) is essential for emerging dispersion-based energy-conscious technologies. Of particular interest are micro- and macro-scale self-organizing superstructures that can bridge 2D/3D processing scales. Here we report the spontaneous assembly of CdTe NPs within an aqueous microdroplet suspended in soybean oil. The gradual diffusion of the water into the surrounding medium results in shrinking of the microdroplet, and a concomitant formation of branched assemblies from CdTe NPs that evolve in size from ∼50 μm to ∼1000 μm. The fractal dimension of NP assemblies increases from ∼1.7 to ∼1.9 during the assembly process. We found that constituents of the soybean oil enter the aqueous solution across the microdroplet interface and affect NP assembly. The obtained NP dendrites can be further altered morphologically by illumination with light that results in the disassembly of the NP dendrites. The use of this microheterogeneous dispersion platform with partially soluble hydrophilic and hydrophobic solvents highlights the sensitivity of the NP assembly process to environment and presents an opportunity to explore droplet-confined NP assembly

Biomimetics: Antimicrobial Microwebs of DNA–Histone Inspired from Neutrophil Extracellular Traps (Adv. Mater. 14/2019)

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149239/1/adma201970097.pd

Biomimetics: Antimicrobial Microwebs of DNA–Histone Inspired from Neutrophil Extracellular Traps (Adv. Mater. 14/2019)

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149239/1/adma201970097.pd

Extracellular Trap‐Mimicking DNA‐Histone Mesostructures Synergistically Activate Dendritic Cells

Extracellular traps (ETs), such as neutrophil extracellular traps, are a physical mesh deployed by immune cells to entrap and constrain pathogens. ETs are immunogenic structures composed of DNA, histones, and an array of variable protein and peptide components. While much attention has been paid to the multifaceted function of these structures, mechanistic studies of ETs remain challenging due to their heterogeneity and complexity. Here, a novel DNA‐histone mesostructure (DHM) formed by complexation of DNA and histones into a fibrous mesh is reported. DHMs mirror the DNA‐histone structural frame of ETs and offer a facile platform for cell culture studies. It is shown that DHMs are potent activators of dendritic cells and identify both the methylation state of DHMs and physical interaction between dendritic cells and DHMs as key tuning switches for immune stimulation. Overall, the DHM platform provides a new opportunity to study the role of ETs in immune activation and pathophysiology.A novel DNA‐histone mesostructure (DHM) platform is reported, which mirrors the morphology of extracellular traps (ETs). This platform enables bottom‐up cell‐based assays to determine the role of the DNA‐histone substructure in ET‐associated phenomena. Here, DHMs are used to investigate ET‐mediated immunostimulation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152974/1/adhm201900926.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152974/2/adhm201900926_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152974/3/adhm201900926-sup-0001-SuppMat.pd