Manuel Marquez

Bio: Manuel Marquez is an academic researcher from University of North Texas. The author has contributed to research in topics: Electrospinning & Atmospheric pressure. The author has an hindex of 38, co-authored 109 publications receiving 6990 citations. Previous affiliations of Manuel Marquez include Yale University & University of Málaga.

Micro/Nano Encapsulation via Electrified Coaxial Liquid Jets

Abstract: We report a method to generate steady coaxial jets of immiscible liquids with diameters in the range of micrometer/nanometer size. This compound jet is generated by the action of electro-hydrodynamic (EHD) forces with a diameter that ranges from tens of nanometers to tens of micrometers. The eventual jet breakup results in an aerosol of monodisperse compound droplets with the outer liquid surrounding or encapsulating the inner one. Following this approach, we have produced monodisperse capsules with diameters varying between 10 and 0.15 micrometers, depending on the running parameters.

Ultrahigh-throughput screening in drop-based microfluidics for directed evolution

Abstract: The explosive growth in our knowledge of genomes, proteomes,and metabolomes is driving ever-increasing fundamental under-standing of the biochemistry of life, enabling qualitatively newstudies of complex biological systems and their evolution. Thisknowledge also drives modern biotechnologies, such as molecularengineeringandsyntheticbiology, whichhaveenormouspotentialto address urgent problems, including developing potent newdrugs and providing environmentally friendly energy. Many ofthese studies, however, are ultimately limited by their need foreven-higher-throughput measurements of biochemical reactions.We present a general ultrahigh-throughput screening platformusing drop-based microfluidics that overcomes these limitationsand revolutionizes both the scale and speed of screening. Weuse aqueous drops dispersed in oil as picoliter-volume reactionvessels and screen them at rates of thousands per second. To dem-onstrate its power, we apply the system to directed evolution,identifyingnewmutantsoftheenzymehorseradishperoxidaseex-hibiting catalytic rates more than 10 times faster than their parent,which is already a very efficient enzyme. We exploit the ultrahighthroughput to use an initial purifying selection that removes inac-tive mutants; we identify ∼100 variants comparable in activity tothe parent from an initial population of ∼10

Correction for Ultrahigh-throughput screening in drop-based microfluidics for directed evolution

Abstract: The explosive growth in our knowledge of genomes, proteomes, and metabolomes is driving ever-increasing fundamental understanding of the biochemistry of life, enabling qualitatively new studies of complex biological systems and their evolution. This knowledge also drives modern biotechnologies, such as molecular engineering and synthetic biology, which have enormous potential to address urgent problems, including developing potent new drugs and providing environmentally friendly energy. Many of these studies, however, are ultimately limited by their need for even-higher-throughput measurements of biochemical reactions. We present a general ultrahigh-throughput screening platform using drop-based microfluidics that overcomes these limitations and revolutionizes both the scale and speed of screening. We use aqueous drops dispersed in oil as picoliter-volume reaction vessels and screen them at rates of thousands per second. To demonstrate its power, we apply the system to directed evolution, identifying new mutants of the enzyme horseradish peroxidase exhibiting catalytic rates more than 10 times faster than their parent, which is already a very efficient enzyme. We exploit the ultrahigh throughput to use an initial purifying selection that removes inactive mutants; we identify ∼100 variants comparable in activity to the parent from an initial population of ∼107. After a second generation of mutagenesis and high-stringency screening, we identify several significantly improved mutants, some approaching diffusion-limited efficiency. In total, we screen ∼108 individual enzyme reactions in only 10 h, using < 150 μL of total reagent volume; compared to state-of-the-art robotic screening systems, we perform the entire assay with a 1,000-fold increase in speed and a 1-million-fold reduction in cost.

Glass-like dynamics of collective cell migration

Abstract: Collective cell migration in tissues occurs throughout embryonic development, during wound healing, and in cancerous tumor invasion, yet most detailed knowledge of cell migration comes from single-cell studies. As single cells migrate, the shape of the cell body fluctuates dramatically through cyclic processes of extension, adhesion, and retraction, accompanied by erratic changes in migration direction. Within confluent cell layers, such subcellular motions must be coupled between neighbors, yet the influence of these subcellular motions on collective migration is not known. Here we study motion within a confluent epithelial cell sheet, simultaneously measuring collective migration and subcellular motions, covering a broad range of length scales, time scales, and cell densities. At large length scales and time scales collective migration slows as cell density rises, yet the fastest cells move in large, multicell groups whose scale grows with increasing cell density. This behavior has an intriguing analogy to dynamic heterogeneities found in particulate systems as they become more crowded and approach a glass transition. In addition we find a diminishing self-diffusivity of short-wavelength motions within the cell layer, and growing peaks in the vibrational density of states associated with cooperative cell-shape fluctuations. Both of these observations are also intriguingly reminiscent of a glass transition. Thus, these results provide a broad and suggestive analogy between cell motion within a confluent layer and the dynamics of supercooled colloidal and molecular fluids approaching a glass transition.

Electrospinning: A Simple and Versatile Technique for Producing Ceramic Nanofibers and Nanotubes

Abstract: Electrospinning is a remarkably simple method for generating nanofibers of polymers. When combined with conventional sol–gel processing, it provides a versatile technique for producing ceramic nanofibers with either a solid, porous, or hollow structure. This article presents a brief overview of recent progress in preparation of ceramic nanofibers by electrospinning, with a focus on an introduction to experimental procedures and analysis of several technical issues that are vital for a successful electrospinning experiment. We also highlight the unique capabilities of this technique in processing ceramic materials into nanostructures, and illustrate some potential applications of these nanostructures.

Electrospinning: a fascinating fiber fabrication technique.

Abstract: With the emergence of nanotechnology, researchers become more interested in studying the unique properties of nanoscale materials. Electrospinning, an electrostatic fiber fabrication technique has evinced more interest and attention in recent years due to its versatility and potential for applications in diverse fields. The notable applications include in tissue engineering, biosensors, filtration, wound dressings, drug delivery, and enzyme immobilization. The nanoscale fibers are generated by the application of strong electric field on polymer solution or melt. The non-wovens nanofibrous mats produced by this technique mimics extracellular matrix components much closely as compared to the conventional techniques. The sub-micron range spun fibers produced by this process, offer various advantages like high surface area to volume ratio, tunable porosity and the ability to manipulate nanofiber composition in order to get desired properties and function. Over the years, more than 200 polymers have been electropun for various applications and the number is still increasing gradually with time. With these in perspectives, we aim to present in this review, an overview of the electrospinning technique with its promising advantages and potential applications. We have discussed the electrospinning theory, spinnable polymers, parameters (solution and processing), which significantly affect the fiber morphology, solvent properties and melt electrospinning (alternative to solution electrospinning). Finally, we have focused on varied applications of electrospun fibers in different fields and concluded with the future prospects of this efficient technology.

Electrospinning: A Fascinating Method for the Preparation of Ultrathin Fibers

Abstract: Electrospinning is a highly versatile method to process solutions or melts, mainly of polymers, into continuous fibers with diameters ranging from a few micrometers to a few nanometers. This technique is applicable to virtually every soluble or fusible polymer. The polymers can be chemically modified and can also be tailored with additives ranging from simple carbon-black particles to complex species such as enzymes, viruses, and bacteria. Electrospinning appears to be straightforward, but is a rather intricate process that depends on a multitude of molecular, process, and technical parameters. The method provides access to entirely new materials, which may have complex chemical structures. Electrospinning is not only a focus of intense academic investigation; the technique is already being applied in many technological areas.

Poly Lactic-co-Glycolic Acid (PLGA) as Biodegradable Controlled Drug Delivery Carrier

Abstract: In past two decades poly lactic-co-glycolic acid (PLGA) has been among the most attractive polymeric candidates used to fabricate devices for drug delivery and tissue engineering applications. PLGA is biocompatible and biodegradable, exhibits a wide range of erosion times, has tunable mechanical properties and most importantly, is a FDA approved polymer. In particular, PLGA has been extensively studied for the development of devices for controlled delivery of small molecule drugs, proteins and other macromolecules in commercial use and in research. This manuscript describes the various fabrication techniques for these devices and the factors affecting their degradation and drug release.

Hydrodynamics of soft active matter

Abstract: This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are ``dry'' systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or ``wet'' systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

Droplet Barcoding for Single-Cell Transcriptomics Applied to Embryonic Stem Cells

Abstract: It has long been the dream of biologists to map gene expression at the single-cell level With such data one might track heterogeneous cell sub-populations, and infer regulatory relationships between genes and pathways Recently, RNA sequencing has achieved single-cell resolution What is limiting is an effective way to routinely isolate and process large numbers of individual cells for quantitative in-depth sequencing We have developed a high-throughput droplet-microfluidic approach for barcoding the RNA from thousands of individual cells for subsequent analysis by next-generation sequencing The method shows a surprisingly low noise profile and is readily adaptable to other sequencing-based assays We analyzed mouse embryonic stem cells, revealing in detail the population structure and the heterogeneous onset of differentiation after leukemia inhibitory factor (LIF) withdrawal The reproducibility of these high-throughput single-cell data allowed us to deconstruct cell populations and infer gene expression relationships VIDEO ABSTRACT