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Sökning: L773:1387 2176 OR L773:1572 8781

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1.
  • Chu, Jiangtao, et al. (författare)
  • Impact of static pressure on transmembrane fluid exchange in high molecular weight cut off microdialysis
  • 2014
  • Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 16:2, s. 301-310
  • Tidskriftsartikel (refereegranskat)abstract
    • With the interest of studying larger biomolecules by microdialysis (MD), this sampling technique has reached into the ultrafiltration region of fluid exchange, where fluid recovery (FR)  has a strong dependence on pressure. Hence in this study, we focus on the fluid exchange across the high molecular weight cut off MD membrane under the influence of the static pressure in the sampling environment. A theoretical model is presented for MD with such membranes, where FR has a linear dependence upon the static pressure of the sample. Transmembrane (TM) osmotic pressure difference and MD perfusion rate decide how fast FR increases with increased static pressure.A test chamber for in vitro MD under static pressure was constructed and validated. It can hold four MD probes under controlled pressurized conditions. Comparison showed good agreement between experiment and theory. Moreover, test results showed that the fluid recovery of the test chamber MD can be set accurately via the chamber pressure, which is controlled by sample injection into the chamber at precise rate. This in vitro system is designed for modelling in vivo MD in cerebrospinal fluid and studies with biological samples in this system may be good models for in vivo MD. 
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2.
  • Chu, Jiangtao, 1982-, et al. (författare)
  • Influence of different pluronic surface modifications and pressure on microdialysis protein extraction efficiency
  • 2015
  • Ingår i: Biomedical microdevices (Print). - Springer. - 1387-2176 .- 1572-8781.
  • Tidskriftsartikel (refereegranskat)abstract
    • There is growing interest in using microdialysis (MD) for monitoring larger and more complexmolecules such as neuropeptides and proteins. This promotes the use of MD membranes withmolecular weight cut off (MWCO) of 100 kDa. Hence, the hydrodynamic property of themembrane goes to ultrafiltration, making the sampling more sensitive to pressure changes. Also,despite the large membrane pore size, studies have shown that membrane biofouling still leads tounstable catheter performance. Our objective is to study in vitro how four kinds of surfacemodifications (Pluronic L31, L44, F87 and F127+L31) affect the fluid recovery (FR) andextraction efficiency (EE) of 100 kDa MWCO MD catheters, under controlled pressure. Apressure chamber was employed to facilitate the tests, using as MD sample a protein standardwith proteins of similar concentrations as in human cerebral spinal fluid. The collected dialysatefractions were examined for FR and EE. Targeted mass spectrometry analysed the EE ofindividual proteins and peptides. The thicker the pluronic adsorption layer, the less thehydrodynamic diameter of the membrane pores, leading to lower and more stable FR. The foursurface modifications had three different behaviours: Pluronic F127 + L31 showed similarbehavior to the Pluronic F127 and the native original membrane; Pluronic F87 showed acontinuous EE increase with pressure; Pluronic L31 and L44 showed similar EE values, whichwere stable with pressure. Different surface modifications are clearly selective to differentproteins and peptides. We conclude that a pluronic surface modification could provide MDsampling with more stable FR, and more stable or enhanced EE with high FR, depending on theobjective of the sampling.
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3.
  • Chu, Jiangtao, 1982-, et al. (författare)
  • Influence of surface modification and static pressure on microdialysis protein extraction efficiency
  • 2015
  • Ingår i: Biomedical microdevices (Print). - Springer : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 17:5
  • Tidskriftsartikel (refereegranskat)abstract
    • There is growing interest in using microdialysis (MD) for monitoring larger and more complexmolecules such as neuropeptides and proteins. This promotes the use of MD membranes withmolecular weight cut off (MWCO) of 100 kDa or above. The hydrodynamic property of themembrane goes to ultrafiltration or beyond, making the MD catheters more sensitive to pressure.In the meantime, despite the large pore size, studies have shown that membrane biofouling stilllead to unstable catheter performance. The objective is to study in vitro how 500 kDa dextranand Poloxamer 407 surface modification affect the fluid recovery (FR) and extraction efficiency(EE) of 100 kDa MWCO MD catheters. A pressure chamber was designed to facilitate the tests,using as MD sample a protein standard with similar concentrations as in human cerebral spinalfluid, comparing native and Poloxamer 407 modified MD catheters. The collected dialysatefractions were examined for FR and protein EE, employing Dot-it Spot-it Protein Assay for totalprotein EE and targeted mass spectrometry (MS) for EE of individual proteins and peptides. TheFR results suggested that the surface modified catheters were less sensitive to the pressure andprovide higher precision, and provided a FR closer to 100%. The surface modification did notshow a significant effect on the protein EE. The average total protein EE of surface modifiedcatheters was slightly higher than that of the native ones. The MS EE data of individual proteinsshowed a clear trend of complex response in EE with pressure.
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4.
  • Dånmark, Staffan, et al. (författare)
  • Development of a novel microfluidic device for long-term in situ monitoring of live cells in 3-dimensional matrices
  • 2012
  • Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 14:5, s. 885-893
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the latest innovations in microfabrication technology, 3-dimensional microfluidic cell culture systems have been developed as an attractive alternative to traditional 2-dimensional culturing systems as a model for long-term microscale cell-based research. Most microfluidic systems are based on the embedding of cells in hydrogels. However, physiologically realistic conditions based on hydrogels are difficult to obtain and the systems are often too complicated. We have developed a microfluidic cell culture device that incorporates a biodegradable rigid 3D polymer scaffold using standard soft lithography methods. The device permits repeated high-resolution fluorescent imaging of live cell populations within the matrix over a 4 week period. It was also possible to track cell development at the same spatial location throughout this time. In addition, human primary periodontal ligament cells were induced to produce quantifiable calcium deposits within the system. This simple and versatile device should be readily applicable for cell-based studies that require long-term culture and high-resolution bioimaging.
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5.
  • Faridi, Muhammad Asim, et al. (författare)
  • Glass Capillary based cavity resonator for particle trapping study and bacteria up-concentration
  • Ingår i: Biomedical microdevices (Print). - 1387-2176 .- 1572-8781.
  • Tidskriftsartikel (refereegranskat)abstract
    • We have performed particle aggregation characterization on the basis of their material and suspendingmedium in a capillary-based cavity resonator used for acoustophoresis. We have investigated the experimentalaggregation time of 5μm polystyrene and silica particles, size of aggregate, number of trapped particles and upconcentrationfactor in water, 0.01M phosphate buffered saline (PBS) and 0.005M PBS at 1.97MHz and withactuation voltages between 4, 8 and 12Vpp. We have found that there is little difference between using water andPBS as suspension medium, approximately 5-10% longer trapping times with PBS compared with water.However we get approx. 5.5 times faster trapping time for silica than for polystyrene. It is also observed andcalculated that silica particle aggregates have 3.4 times larger area than the polystyrene aggregates using the samestarting particle concentrations, revealing similar amount of difference in trapped number of particles. The upconcentrationfactor for silica is also about 3.2 times higher than that of polystyrene due to larger aggregate areaof silica particles. Based on theoretical predictions and experimental characterization of the particle aggregationpattern, we note that the particle-particle interaction force contribution to the total acoustic radiation force is morepronounced for silica than for polystyrene. Finally as a proof of principle for biomedical sample preparationapplication we demonstrate the capillary-based silica particles mediated bacteria acoustophoretic upconcentration.This setup could potentially be utilized not only for sample preparation application but also forbead based affinity immunoassays.
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6.
  • Faridi, Muhammad Asim, et al. (författare)
  • MicroBubble Activated Acoustic Cell Sorting : BAACS
  • Ingår i: Biomedical microdevices (Print). - 1387-2176 .- 1572-8781.
  • Tidskriftsartikel (refereegranskat)abstract
    • Acoustophoresis, the ability to acoustically manipulate particles and cells inside a microfluidic channel, is a critical enabling technology for cell-sorting applications. However, one of the major impediments for routine use of acoustophoresis at clinical laboratory has been the reliance on the inherent physical properties of cells for separation. Here, we present a microfluidic-based microBubble-Activated Acoustic Cell Sorting (BAACS) method that rely on the specific binding of target cells to microbubbles conjugated with specific antibodies on their surface for continuous cell separation using ultrasonic standing wave. In acoustophoresis, cells being positive acoustic contrast particles migrate to pressure nodes. On the contrary we show that air-filled polymer-shelled microbubbles being strong negative acoustic contrast particles migrate to pressure antinodes at acoustic pressure amplitudes as low as 60 kPa. As a proof of principle, using the BAACS strategy, we demonstrate the separation of cancer cell line in a suspension with better than 75% efficiency. Moreover, 100% of the microbubble-cell conjugates migrated to the anti-node. Hence a better upstream affinity-capture has the potential to provide higher sorting efficiency. The BAACS technique may potentially provide a simplistic approach for similar sized selective isolation of cells, and is suited for applications in point of care.
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7.
  • Faridi, Muhammad Asim, et al. (författare)
  • MicroBubble Activated Acoustic Cell Sorting : BAACS
  • 2017
  • Ingår i: Biomedical microdevices (Print). - : Springer. - 1387-2176 .- 1572-8781. ; 19:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Acoustophoresis, the ability to acoustically manipulate particles and cells inside a microfluidic channel, is a critical enabling technology for cell-sorting applications. However, one of the major impediments for routine use of acoustophoresis at clinical laboratory has been the reliance on the inherent physical properties of cells for separation. Here, we present a microfluidic-based microBubble-Activated Acoustic Cell Sorting (BAACS) method that rely on the specific binding of target cells to microbubbles conjugated with specific antibodies on their surface for continuous cell separation using ultrasonic standing wave. In acoustophoresis, cells being positive acoustic contrast particles migrate to pressure nodes. On the contrary we show that air-filled polymer-shelled microbubbles being strong negative acoustic contrast particles migrate to pressure antinodes at acoustic pressure amplitudes as low as 60 kPa. As a proof of principle, using the BAACS strategy, we demonstrate the separation of cancer cell line in a suspension with better than 75% efficiency. Moreover, 100% of the microbubble-cell conjugates migrated to the anti-node. Hence a better upstream affinity-capture has the potential to provide higher sorting efficiency. The BAACS technique may potentially provide a simplistic approach for similar sized selective isolation of cells, and is suited for applications in point of care.
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8.
  • Frisk, Thomas, et al. (författare)
  • A silicon-glass microwell platform for high-resolution imaging and high-content screening with single cell resolution
  • 2011
  • Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 13:4, s. 683-693
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a novel microwell array platform suited for various cell-imaging assays where single cell resolution is important. The platform consists of an exchangeable silicon-glass microchip for cell biological applications and a custom made holder that fits in conventional microscopes. The microchips presented here contain arrays of miniature wells, where the well sizes and layout have been designed for different applications, including single cell imaging, studies of cell-cell interactions or ultrasonic manipulation of cells. The device has been designed to be easy to use, to allow long-term assays (spanning several days) with read-outs based on high-resolution imaging or high-content screening. This study is focused on screening applications and an automatic cell counting protocol is described and evaluated. Finally, we have tested the device and automatic counting by studying the selective survival and clonal expansion of 721.221 B cells transfected to express HLA Cw6-GFP compared to untransfected 721.221 B cells when grown under antibiotic selection for 3 days. The device and automated analysis protocol make up the foundation for development of several novel cellular imaging assays.
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9.
  • Iranmanesh, Ida, et al. (författare)
  • Acoustic micro-vortexing of fluids, particles and cells in disposable microfluidic chips
  • 2016
  • Ingår i: Biomedical microdevices (Print). - : Springer. - 1387-2176 .- 1572-8781. ; 18:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate an acoustic platform for microvortexing in disposable polymer microfluidic chips with small-volume (20 mu l) reaction chambers. The described method is demonstrated for a variety of standard vortexing functions, including mixing of fluids, re-suspension of a pellet of magnetic beads collected by a magnet placed on the chip, and lysis of cells for DNA extraction. The device is based on a modified Langevin-type ultrasonic transducer with an exponential horn for efficient coupling into the microfluidic chip, which is actuated by a low-cost fixed-frequency electronic driver board. The transducer is optimized by numerical modelling, and different demonstrated vortexing functions are realized by actuating the transducer for varying times; from fractions of a second for fluid mixing, to half a minute for cell lysis and DNA extraction. The platform can be operated during 1 min below physiological temperatures with the help of a PC fan, a Peltier element and an aluminum heat sink acting as the chip holder. As a proof of principle for sample preparation applications, we demonstrate on-chip cell lysis and DNA extraction within 25 s. The method is of interest for automating and chip-integrating sample preparation procedures in various biological assays.
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10.
  • Jager, Edwin W.H., et al. (författare)
  • The cell clinic : closable microvials for single cell studies
  • 2002
  • Ingår i: Biomedical microdevices (Print). - 1387-2176 .- 1572-8781. ; 4:3, s. 177-187
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the development of a cell clinic. This is a micromachined cavity, or microvial, that can be closed with a lid. The lid is activated by two polypyrrole/Au microactuators. Inside the microvials two Au electrodes have been placed in order to perform impedance studies on single or a small number of cells. We report on impedance measurements on Xenopus leavis melanophores. We could measure a change in the impedance upon cell spreading and identify intracellular events such as the aggregation of pigment granules. The electrical data is correlated to optical microscopy.
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