3,940 research outputs found
Highly Tailorable and Monodisperse Porous Beads via Microfluidics
No full textIn tissue engineering practice, a scaffold is often needed to deliver cells to the desired body site needing to be repaired. Scaffolds supporting cells can be either implanted through a surgical operation or injected through a laparoscopic device. The latter option is a first-choice in cases where a small and irregularly shaped defect needs to be regenerated. In such circumstances, the cell carrier has to be miniaturised while maintaining the morphological features that make a scaffold an efficient cell culture support, i.e. a uniform and adequate porous texture in terms of pore and interconnect dimensions. In this work, we illustrate a novel and powerful method for the manufacturing of monodisperse porous beads of tailorable dimension (in the range ~ 300÷1500 m) and with an internal porous texture characterised by uniformly sized and fully interconnected pores. The fabrication method relies on the use of a flow-focusing microfluidic chip that generates a monodisperse oil-in-water emulsion (panel b). The aqueous phase of the emulsion contains a biopolymer and an appropriate surfactant. Here, we demonstrate that by extruding the emulsion through a needle immersed in a perfluorinated oil on top of which a coagulating aqueous bath is stratified and by applying a pulsed electrical field (panel a), it is possible to precisely control the size of the emulsion droplets detached from the needle. As soon as the emulsion droplets reach the interface between the perfluorinated oil and coagulating bath, they instantaneously solidify. An inverse relationship exist between intensity of the applied voltage and beads dimension (panels c,d,e). The presented process is very repeatable and brings about to beads rigorously monodisperse in size (panel f). Finally, such microbeads demonstrated to be a successful cell carrier.In tissue engineering practice, a scaffold is often needed to deliver cells to the desired body site needing to be repaired. Scaffolds supporting cells can be either implanted through a surgical operation or injected through a laparoscopic device. The latter option is a first-choice in cases where a small and irregularly shaped defect needs to be regenerated. In such circumstances, the cell carrier has to be miniaturised while maintaining the morphological features that make a scaffold an efficient cell culture support, i.e. a uniform and adequate porous texture in terms of pore and interconnect dimensions. In this work, we illustrate a novel and powerful method for the manufacturing of monodisperse porous beads of tailorable dimension (in the range ~ 300÷1500 m) and with an internal porous texture characterised by uniformly sized and fully interconnected pores. The fabrication method relies on the use of a flow-focusing microfluidic chip that generates a monodisperse oil-in-water emulsion (panel b). The aqueous phase of the emulsion contains a biopolymer and an appropriate surfactant. Here, we demonstrate that by extruding the emulsion through a needle immersed in a perfluorinated oil on top of which a coagulating aqueous bath is stratified and by applying a pulsed electrical field (panel a), it is possible to precisely control the size of the emulsion droplets detached from the needle. As soon as the emulsion droplets reach the interface between the perfluorinated oil and coagulating bath, they instantaneously solidify. An inverse relationship exist between intensity of the applied voltage and beads dimension (panels c,d,e). The presented process is very repeatable and brings about to beads rigorously monodisperse in size (panel f). Finally, such microbeads demonstrated to be a successful cell carrier
Highly ordered and tunable polyHIPEs by using microfluidics
No full textWe demonstrate how to generate highly ordered porous matrices from dextran-methacrylate (DEX-MA) using microfluidics. We use a flow focusing device to inject an aqueous solution of DEX-MA and surfactant to break the flow of an organic solvent (cyclohexane) into monodisperse droplets at a high volume fraction (above 74% v/v) to form an ordered high internal phase emulsion (HIPE). We collect the crystalline HIPE structure and freeze it by gelling. The resulting polyHIPEs are characterized by an interconnected and ordered morphology. The size of pores and interconnects ranges between hundreds and tens of micrometers, respectively. The technique that we describe allows for precise tuning of all the structural parameters of the matrices, including their porosity, the size of the pores and the lumen of interconnects between the pores. The resulting ordered and precisely tailored HIPE gels represent a new class of scaffolds for applications in tissue engineering.We demonstrate how to generate highly ordered porous matrices from dextran-methacrylate (DEX-MA) using microfluidics. We use a flow focusing device to inject an aqueous solution of DEX-MA and surfactant
to break the flow of an organic solvent (Cycle-Hexane) into monodisperse droplets at high volume fraction (above 74% v/v) to form an ordered high internal phase emulsion (HIPE). We collect the crystalline HIPE structure and freeze it by gelling. The resulting polyHIPEs are characterized by an interconnected and ordered morphology. The size of pores and interconnects ranges between hundreds and tens micrometers, respectively. The technique that we describe allows for precise tuning of all the structural parameters of the matrices, including their porosity, the size of the pores and the lumens of interconnects between the pores. The resulting ordered and precisely tailored HIPE gels represent a new
class of scaffolds for applications in tissue engineering
About art of word in "Potrójny z Plauta" by Piotr Ciekliński (selected problems)
No full textThe article deals with the question of the language and the style of drama Potrójny z Plauta by Piotr Ciekliński.
The author of the treatise emphasized the most important components creating the artistic structure of the work, especially regional elements which are so essential for the writings of old literature
About art of word in "Potrójny z Plauta" by Piotr Ciekliński (selected problems)
No full textThe article deals with the question of the language and the style of drama Potrójny
z Plauta by Piotr Ciekliński.
The author of the treatise emphasized the most important components creating the artistic
structure of the work, especially regional elements which are so essential for the writings of
old literature.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej naukę
Microfluidic foaming: a powerful tool for tailoring the morphological and permeability properties of sponge-like biopolymeric scaffolds
No full textOrdered porous polymeric materials can be engineered to present highly ordered pore arrays and uniform and tunable pore size. These features prompted a number of applications in tissue engineering, generation of meta materials, separation and purification of biomolecules and cells. Designing new and efficient vistas for generation of ordered porous materials is still an active area of research. Here we investigate the potential of microfluidic foaming within a flow-focusing (FF) geometry in producing 3D regular sponge-like polymeric matrices with tailored morphological and permeability properties. The challenge in using microfluidic systems for generation of polymeric foams is in the high viscosity of the continuous phase. We demonstrate that as the viscosity of the aqueous solution increases, the accessible range of foam bubble fraction (b) and bubbles diameter (Db) inside the microfluidic chip tend to narrow progressively. This effect limits the accessible range of geometric properties of the resulting materials. We further show that this problem can be rationally tackled by appropriate choice of the concentration of the polymer. We demonstrate that via such optimization, the microfluidic assisted synthesis of porous materials becomes a facile and versatile tool for generation of porous materials with a wide range of pore size and pore volume. Moreover, we demonstrate that the size of interconnects among pores - for a given value of the gas fraction - can be tailored through the variation of surfactant concentration. This in turn, affects the permeability of the materials, a factor of key importance in flow-through applications and in tissue engineering
Wall fluidization in two acts: from stiff to soft roughness
No full textFluidization of soft glassy materials (SGMs) in microfluidic channels is affected by the wall roughness in the form of microtexturing. When SGMs flow across microgrooves, their constituents are likely trapped within the grooves’ gap, and the way they are released locally modifies the fluidization close to the walls. By leveraging a suitable combination of experiments and numerical simulations on concentrated emulsions (a model SGM), we quantitatively report the existence of two physically different scenarios. When the gap is large compared to the droplets in the emulsion, the droplets hit the solid obstacles and easily escape scrambling with their neighbors. Conversely, as the gap spacing is reduced, droplets get trapped inside, creating a ‘‘soft roughness’’ layer, i.e. a complementary series of deformable posts from which overlying droplets are in turn released. In both cases, the induced fluidization scales with the grooves’ density, although with a reduced prefactor for narrow gaps, accounting for the softness of the roughness. Both scenarios are also well distinguished via the statistics of the droplets displace- ment field close to the walls, with large deviations induced by the surface roughness, depending on its stiffness
3D printing of functionally graded porous materials using on-demand reconfigurable microfluidics
No full textTailoring the morphology of macroporous structures remains one of the biggest challengesin material synthesis. Here, we present an innovative approach to fabricatecustommacroporous materials with pore size varying throughout the structure by up to an order of magnitudeusingon-demand reconfigurable microfluidics. We employavalve-based flow-focusing junction(vFF)in which the size of the orifice can be adjusted in real-time (within tens of milliseconds)to generate foams withon-linecontrolled bubble size. We use the junction tofabricatelayered and smoothly graded porous structureswith pore size varying in the range 80-800 μm.Additionally, to further exploit thecapacityof the technique, we mount vFF on top of an extrusion printer and 3D-print constructscharacterized by a predefined 3D geometryand controlled spatiallyvaryinginternal porous architecture, such asa model of a bone. The presented technology opensup new possibilities in macroporous material synthesis with potential applications ranging from tissue engineering to aerospace industry and construction
Władza — etyka — egzystencja (uwagi o powieści Piotra Aleszkowskiego „Twierdza”)
No full textUsing metaphorical connotations terms functioning within postcolonial theory, the author analyzes mechanisms ruling the world of the novel Fortress (Крепость) by Piotr Aleshkovsky.Using metaphorical connotations terms functioning within postcolonial theory, the author analyzes mechanisms ruling the world of the novel Fortress (Крепость) by Piotr Aleshkovsky
Detection and enumeration of bacteria by pump-free digital droplet assays
No full textBacteria are present in all sections of our life. However, in order to assess and control health threats, it is necessary to detect and enumerate critical bacterial species in order to prevent bacteria outbreak, diagnose bacterial infections, to provide a proper treatment and further to avoid antibiotic abuses. Current techniques for detection and enumeration of bacteria are time-consuming, labor-intensive, often lack of precision, or require additional calibration strategies. Although digital droplet assays provide an opportunity for absolute quantification of bacteria and can reduce the time-to-result, the current droplet microfluidic setups for bacterial enumeration have a low degree of integration and parallelization, comprise complicated manual handling steps and need external interfaces such as connecting tubings. Therefore, there is a need to fill these gaps.This thesis presents the implementation approaches of three bacterial detection assays that use pump-free step emulsification cartridges for digital detection and quantification of bacteria. The first implementation was the integration of a resazurin reduction assay on a newly developed gravity-driven step emulsification device for universal bacterial detection and enumeration being applied to a digital antibiotic susceptibility test. The four-chamber gravity-driven step emulsification device allowed encapsulation of bacteria suspension in 2000 of 2 nl droplets into each chamber. The manual workload for droplet generation involved merely sample preparation, loading the sample mixture into the sample inlet of the device, and subsequently orienting the device vertically for gravity-driven emulsification. Thereby, no additional pumping system was required. In the digital detection and enumeration assay, the resazurin was reduced to fluorescent resorufin in the presence of viable bacteria and the quantification of bacteria was reduced from 18–24 hours down to 5 hours. Decimal dilution series showed a high degree of linearity of the assay for the bacterial species: Escherichia coli (R2=0.9985), Staphylococcus aureus (R2=0.9998), and Enterococcus faecalis (R2=0.9992).The second implementation was the integration of a generic enzymatic substrate method by using resorufin β-D-glucuronide on centrifugal step emulsification cartridge (DropChip) for detection and enumeration of Escherichia coli. A two-chamber DropChip generated 35600 ofiv0.42 nl droplets in each chamber with the aid of a standard laboratory mini-centrifuge. Methyl-β-D-glucuronide was used to induce the production of β-D-glucuronidase in Escherichia coli so that resorufin β-D-glucuronide was hydrolyzed and released a fluorophore for signal detection. The digital enumeration of Escherichia coli can be achieved in 4.5 hours and displayed high correlations (R2=0.9999) with the standard plate count.The third implementation was the integration of a one-pot wash-free fluorescence in situ hybridization assay on a centrifugal step emulsification cartridge (LabDisk) for universal but gene specific bacterial detection and enumeration. A ten-chamber LabDisk generated 47600 of 0.21 nl droplets per chamber with the aid of a customized centrifuge (LabDisk Player). The method offers minimal manual workload – it requires only mixing of the sample with the reagents and loading it into a cartridge for partitioning of the bacteria into droplets for in situ permeabilization, hybridization and signal detection. Optimized LNA/DNA molecular beacons targeted the universal region of bacterial 16S ribosomal RNA and allowed visualization of bacteria at single cell level. The assay was characterized with Escherichia coli, Klebsiella pneumonia, and Proteus mirabilis with single-cell sensitivity and a linearity of R2=0.9760 for all data points including variation of the three tested bacteria models. The total time-to-result of digital enumeration of bacteria was around 1.5 hours.In conclusion, this thesis provides easy-to-use pump-free digital droplet assay solutions for same day timely bacteria detection and enumeration with minimal manual handling steps and simple workflow. The presented three methods are capable to pave the way for further implementation in point-of-care detection systems in the future
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