| 1. |
- Chiu, D T, et al.
(författare)
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Chemical transformations in individual ultrasmall biomimetic containers
- 1999
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Ingår i: Science. - Stanford Univ, Dept Chem, Stanford, CA 94305 USA. Univ Gothenburg, Dept Chem, S-41296 Gothenburg, Sweden. Pomona Coll, Dept Chem, Claremont, CA 91711 USA. : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 283:5409, s. 1892-1895
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Tidskriftsartikel (refereegranskat)abstract
- Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes.
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| 2. |
- Chiu, D T, et al.
(författare)
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Manipulating the biochemical nanoenvironment around single molecules contained within vesicles
- 1999
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Ingår i: Chemical Physics. - Univ Gothenburg, Dept Chem, SE-41296 Gothenburg, Sweden. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. : ELSEVIER. - 0301-0104 .- 1873-4421. ; 247:1, s. 133-139
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Tidskriftsartikel (refereegranskat)abstract
- A method to study single-molecule reactions confined in a biomimetic container is described. The technique combines rapid vesicle preparation, optical trapping and fluorescence confocal microscopy for performing simultaneous single-vesicle trapping and single-molecule detection experiments. The collisional environment between a single enzyme and substrate inside a vesicle is characterized by a Brownian dynamics Monte Carlo simulation. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 3. |
- Strömberg, Anette, et al.
(författare)
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Manipulating the genetic identity and biochemical surface properties of individual cells with electric-field-induced fusion
- 2000
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - Stanford Univ, Dept Chem, Stanford, CA 94305 USA. Gothenburg Univ, Dept Chem, S-41296 Gothenburg, Sweden. Sahlgrens Univ Hosp, Inst Clin Neurosci, Dept Neurol, S-41345 Gothenburg, Sweden. : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 97:1, s. 7-11
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Tidskriftsartikel (refereegranskat)abstract
- A method for cell-cell and cell-liposome fusion at the single-cell level is described. Individual cells or liposomes were first selected and manipulated either by optical trapping or by adhesion to a micromanipulator-controlled ultramicroelectrode. Spatially selective fusion of the cell-cell or cell-liposome pair was achieved by the application of a highly focused electric field through a pair of 5-mu m o.d. carbon-fiber ultramicroelectrodes. The ability to fuse together single cells opens new possibilities in the manipulation of the genetic and cellular makeup of individual cells in a controlled manner, In the study of cellular networks, for example, the alteration of the biochemical identity of a selected cell can have a profound effect on the behavior of the entire network. Fusion of a single liposome with a target cell allows the introduction of the liposomal content into the cell interior as well as the addition of lipids and membrane proteins onto the cell surface. This cell-liposome fusion represents an approach to the manipulation of the cytoplasmic contents and surface properties of single cells. As an example, we have introduced a membrane protein (gamma-glutamyltransferase) reconstituted in liposomes into the cell plasma membrane.
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| 4. |
- Chiu, D T, et al.
(författare)
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Electrical and optical methods for the manipulation and analyses of single cells
- 2001
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Ingår i: CLINICAL DIAGNOSTIC SYSTEMS. - Univ Washington, Dept Chem, Seattle, WA 98195 USA. : SPIE-INT SOC OPTICAL ENGINEERING. - 0819439339 ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- This paper describes the use of focused electric fields and focused optical fields for the high resolution manipulation of single cells. A focused electric field, obtained with the use of ultramicroelectrodes (tip diameter similar to 5 mum), is used to electroporate and electrofuse individual cells selectively and with high spatial resolution. A focused optical field, in the form of an optical tweezer, is used to isolate single organelles from a cell as well as to position liposomes incorporated with receptors and transporters along the cell for the high-resolution sampling and probing of the cellular microenvironment.
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| 5. |
- Karlsson, M, et al.
(författare)
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Electroinjection of colloid particles and biopolymers into single unilamellar liposomes and cells for bioanalytical applications
- 2000
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Ingår i: Analytical Chemistry. - Univ Gothenburg, Dept Chem, SE-41296 Gothenburg, Sweden. Univ Gothenburg, Dept Chem Phys, SE-41345 Gothenburg, Sweden. : AMER CHEMICAL SOC. - 0003-2700 .- 1520-6882. ; 72:23, s. 5857-5862
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Tidskriftsartikel (refereegranskat)abstract
- A combined electroporation and pressure-driven microinjection method for efficient loading of biopolymers and colloidal particles into single-cell-sized unilamellar liposomes was developed. Single liposomes were positioned between a similar to2-mum tip diameter solute-filled glass micropipet, equipped with a Pt electrode, and a 5-mum-diameter carbon fiber electrode. A transient, 1-10 ms, rectangular waveform de voltage pulse (10-40 V/cm) was applied between the electrodes, thus focusing the electric field over the liposome. Dielectric membrane breakdown induced by the applied voltage pulse caused the micropipet tip to enter the liposome and a small volume (typically 50-500 x 10(-15) L) of fluorescein, YOYO-intercalated T7-phage DNA, 100-nm-diameter unilamellar liposomes, or fluorescent latex spheres could be injected into the intraliposomal compartment. We also demonstrate initiation of a chemical intercalation reaction between T2-phage DNA and YOYO-1 by dual injection into a single giant unilamellar liposome. The method was also successfully applied for loading of single cultured cells.
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| 6. |
- Olofsson, Jessica, 1975, et al.
(författare)
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Generation of focused electric field patterns at dielectric surfaces
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:14, s. 4667-4672
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Tidskriftsartikel (refereegranskat)abstract
- We here report on a concept for creating well-defined electric field gradients between the boundaries of capillary electrode (a capillary of a nonconducting material equipped with an interior metal electrode) outlets, and dielectric surfaces. By keeping a capillary electrode opening close to a boundary between a conducting solution and a nonconducting medium, a high electric field can be created close to the interface by field focusing effects. By varying the inner and outer diameters of the capillary, the span of electric field strengths and the field gradient obtained can be controlled, and by varying the slit height between the capillary rim and the surface, or the applied current, the average field strength and gradient can be varied. Field focusing effects and generation of electric field patterns were analyzed using finite element method simulations. We experimentally verified the method by electroporation of a fluorescent dye (fluorescein diphosphate) into adherent, monolayered cells (PC-12 and WSS-1) and obtained a pattern of fluorescent cells corresponding to the focused electric field.
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| 7. |
- Olofsson, Jessica, 1975, et al.
(författare)
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Scanning electroporation of selected areas of adherent cell cultures
- 2007
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 79:12, s. 4410-4418
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Tidskriftsartikel (refereegranskat)abstract
- We present a computer-controlled scanning electroporation method. Adherent cells are electroporated using an electrolyte-filled capillary in contact with an electrode. The capillary can be scanned over a cell culture and locally deliver both an electric field and an electroporation agent to the target area without affecting surrounding cells. The instantaneous size of the targeted area is determined by the dimensions of the capillary. The size and shape of the total electroporated area are defined by these dimensions in combination with the scanning pattern. For example, striped and serpentine patterns of electroporated cells in confluent cultures can be formed. As it is easy to switch between different electroporation agents, the method is suitable for design of cell cultures with complex composition. Finite element method simulations were used to study the spatial distributions of the electric field and the concentration of an electroporation agent, as well as the fluid dynamics related to scanning and flow of electroporation agent from the capillary. The method was validated for transfection by introduction of a 9-base-pair-long randomized oligonucleotide into PC12 cells and a pmaxGFP plasmid coding for green fluorescent protein into CHO and WSS cells.
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| 8. |
- Ryttsen, F., et al.
(författare)
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A Laboratory Method for Determining Bacterially Formed Odorants and Reducing Odor in Absorbent Incontinence Products
- 2019
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Ingår i: Journal of Wound Ostomy and Continence Nursing. - : Ovid Technologies (Wolters Kluwer Health). - 1071-5754. ; 46:6, s. 519-523
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The purpose of this study was to design a laboratory test method to mimic the formation of bacterially formed odorants during the use of absorbent urinary incontinence products. Three odor inhibitors with different modes of action were tested and evaluated. METHODS: Bacterially formed odorants in incontinence products were evaluated by adding a synthetic urine inoculated with a mixture of 4 bacterial strains to product samples cut from the incontinence products. The product samples were incubated in sealed flasks. The odorants that formed in the head space were sampled onto adsorbent tubes and analyzed by gas chromatography. The inhibitory effects of low pH, ethylenediaminetetraacetic acid (EDTA), and activated carbon were then measured. RESULTS: This technique enabled production of known odorants 3-methylbutanal, guaiacol, diacetyl, and dimethyl disulfide (DMDS) in concentrations of 50 to 600 ng/L in incontinence products. The method was further evaluated by testing 3 types of odor inhibitors; EDTA significantly reduced formation of all 4 odorants (P < .001). Lowering the pH from 6.0 to 4.9 decreased levels of 3-methylbutanal, DMDS, and guaiacol (P < .001); however, diacetyl levels increased (P < .001). Activated carbon significantly reduced the formation of diacetyl, DMDS, guaiacol, and 3-methylbutanal (P < .001). CONCLUSIONS: The technique we developed can be used to evaluate inhibitors with different modes of action to determine odor control in incontinence products. The odorants formed are produced by bacteria and have been identified as key contributors to the odor of used incontinence products. This work can be a step toward establishing a standard in the field of incontinence and odor control; creation of a standard will help the health care sector compare products to be purchased and benefit patients through the development of better products.
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| 9. |
- Strömberg, Anette, et al.
(författare)
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Microfluidic device for combinatorial fusion of liposomes and cells
- 2001
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Ingår i: Analytical Chemistry. - Gothenburg Univ, Dept Chem, S-41296 Gothenburg, Sweden. : AMER CHEMICAL SOC. - 0003-2700 .- 1520-6882. ; 73:1, s. 126-130
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Tidskriftsartikel (refereegranskat)abstract
- We describe an electrofusion-based technique for combinatorial synthesis of individual liposomes. A prototype device with containers for liposomes of different compositions and a fusion container was constructed. The sample containers had fluid contact with the fusion container through microchannels. Optical trapping was used to transport individual liposomes and cells through the microchannels into the fusion container. In the fusion container, selected pairs of liposomes were fused together using microelectrodes. A large number of combinatorially synthesized Liposomes with complex compositions and reaction systems can be obtained from small sets of precursor liposomes. The order of different reaction steps can be specified and defined by the fusion sequence. This device could also facilitate single cell-cell electrofusions (hybridoma production). This is exemplified by fusion of transported red blood cells.
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