| 1. |
- Czolkos, Ilja, 1980, et al.
(author)
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Controlled formation and mixing of two-dimensional fluids
- 2007
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 7:7, s. 1980-1984
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Journal article (peer-reviewed)abstract
- We introduce a novel technique for the controlled spreading and mixing of lipid monolayers from multilamellar precursors on surfaces covered by the hydrophobic epoxy resin SU-8. The lipid spreads as a monolayer as a result of the high surface tension between SU-8 and the aqueous environment. A micropatterned device with SU-8 lanes, injection pads, and mixing regions, surrounded by hydrophilic Au, was constructed to allow handling of lipid films and to achieve their mixing at controlled stoichiometry. Our findings offer a new approach to dynamic surface functionalization and decoration as well as surface-based catalysis and self-assembly.
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| 2. |
- Czolkos, Ilja, 1980, et al.
(author)
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Flow control of thermotropic lipid monolayers
- 2011
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In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 7:15, s. 6926-6933
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Journal article (peer-reviewed)abstract
- There is an increasing interest in using liquid crystalline media as mobile phases in two-dimensional nanofluidic systems. Their small-scale, reduced dimensionality, and plentiful opportunities for functionalisation render such phases advantageous. However, flow control has been difficult to achieve, as the wetting processes which drive area expansion are not dynamically controllable. Here, we report on temperature-controlled monolayer spreading of 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE) on the hydrophobic substrates SU-8, and Teflon AF (amorphous fluoropolymer). The gel/liquid phase transition of DEPE at T(c) similar to 38 degrees C is exploited to toggle spreading of a molecular lipid film on SU-8. We observed that on Teflon AF, DEPE monolayer spreading occurs even below T(c), and exhibits strongly accelerated spreading above the phase transition temperature. Our results demonstrate that switching DEPE monolayer spreading on and off, or, alternatively, switching between fast and slow area expansion, is a feasible approach towards establishing control over lipid film flow in two-dimensional fluidic systems. We also present a chip-based device integrating a patterned surface for 2D-microfluidics and on-chip heating.
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| 3. |
- Czolkos, Ilja, 1980, et al.
(author)
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High-Resolution Micropatterned Teflon AF Substrates for Biocompatible Nanofluidic Devices
- 2012
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 28:6, s. 3200-3205
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Journal article (peer-reviewed)abstract
- We describe a general photolithography-based process for the microfabrication of surface-supported Teflon AF structures. Teflon AF patterns primarily benefit from superior optical properties such as very low autofluorescence and a low refractive index. The process ensures that the Teflon AF patterns remain strongly hydrophobic in order to allow rapid lipid monolayer spreading and generates a characteristic edge morphology which assists directed cell growth along the structured surfaces. We provide application examples, demonstrating the well-controlled mixing of lipid films on Teflon AF structures and showing how the patterned surfaces can be used as biocompatible growth-directing substrates for cell culture. Chinese hamster ovary (CHO) cells develop in a guided fashion along the sides of the microstructures, selectively avoiding to grow over the patterned areas.
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| 4. |
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| 5. |
- Czolkos, Ilja, 1980, et al.
(author)
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Molecular phospholipid films on solid supports
- 2011
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In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 7:10, s. 4562-4576
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Journal article (peer-reviewed)abstract
- Phospholipid membranes are versatile structures for mimicking biological surfaces. Bilayer and monolayer membranes can be formed on solid supports, leading to enhanced stability and accessibility of the biomimetic molecular film. This has facilitated functional studies of membrane proteins and aided the development of membrane-based applications in, for example, biosensing, self-assembled reaction kinetics and catalysis. Assembly and preparation of lipid films on supporting surfaces is a challenging engineering task with the goal of fabricating mechanically, chemically and thermodynamically stable lipid membranes. In this review, the current state of the art of molecularly thin lipid layer fabrication is presented with an emphasis on support materials, film formation mechanisms, characterisation methods, and applications.
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| 6. |
- Czolkos, Ilja, 1980, et al.
(author)
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Platform for Controlled Supramolecular Nano-Assembly
- 2009
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 9:6, s. 2482-2486
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Journal article (peer-reviewed)abstract
- We here present a two-dimensional (2D) micro/nano-fluidic technique where reactant-doped liquid−crystal films spread and mix on micro- and nanopatterned substrates. Surface-supported phospholipid monolayers are individually doped with complementary DNA molecules which hybridize when these lipid films mix. Using lipid films to convey reactants reduces the dimensionality of traditional 3D chemistry to 2D, and possibly to 1D by confining the lipid film to nanometer-sized lanes. The hybridization event was observed by FRET using single-molecule-sensitive confocal fluorescence detection. We could successfully detect hybridization in lipid streams on 250 nm wide lanes. Our results show that the number and density of reactants as well as sequence of reactant addition can be controlled within confined liquid crystal films, providing a platform for nanochemistry with potential for kinetic control.
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| 7. |
- Czolkos, Ilja, et al.
(author)
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Prediction of wastewater quality using amperometric bioelectronic tongues
- 2016
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In: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 75, s. 375-382
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Journal article (peer-reviewed)abstract
- Wastewater samples from a Swedish chemi-thermo-mechanical pulp (CTMP) mill collected at different purification stages in a wastewater treatment plant (WWTP) were analyzed with an amperometric enzyme-based biosensor array in a flow-injection system. In order to resolve the complex composition of the wastewater, the array consists of several sensing elements which yield a multidimensional response. We used principal component analysis (PCA) to decompose the array's responses, and found that wastewater with different degrees of pollution can be differentiated. With the help of partial least squares regression (PLS-R), we could link the sensor responses to the Microtox (R) toxicity parameter, as well as to global organic pollution parameters (COD, BOD, and TOC). From investigating the influences of individual sensors in the array, it was found that the best models were in most cases obtained when all sensors in the array were included in the PLS-R model. We find that fast simultaneous determination of several global environmental parameters characterizing wastewaters is possible with this kind of biosensor array, in particular because of the link between the sensor responses and the biological effect onto the ecosystem into which the wastewater would be released. In conjunction with multivariate data analysis tools, there is strong potential to reduce the total time until a result is yielded from days to a few minutes. (C) 2015 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
- Erkan, Yavuz, 1982, et al.
(author)
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Direct immobilization of cholesteryl-TEG-modified oligonucleotides onto hydrophobic SU-8 surfaces
- 2007
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 23:10, s. 5259-5263
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Journal article (peer-reviewed)abstract
- We introduce a rapid, simple one-step procedure for the high-yield immobilization of cholesteryl- tetraethyleneglycol-modified oligonucleotides ( chol- DNA) at hydrophobic sites made of SU-8 photoresist. Topographic structures of SU-8 were microfabricated on microscope glass coverslips sputtered with a Ti/Au layer. Upon application, chol-DNA adsorbed to the SU-8 structures from solution, leaving the surrounding gold surface free of chol- DNA. chol-DNA immobilization is complete within 15 min and yields a surface coverage in the range of 20- 95 pmol/ cm(2), which corresponds to a film density of 10(12)- 10(13) molecules/cm(2). chol-DNA immobilization is stable and can be sustained despite rinsing, drying, dry storage for several hours, and rehydration of chips. Furthermore, complementary DNA in solution hybridizes efficiently to immobilized chol-DNA. We introduce a rapid, simple one-step procedure for the high-yield immobilization of cholesteryl-tetraethyleneglycol-modified oligonucleotides (chol-DNA) at hydrophobic sites made of SU-8 photoresist. Topographic structures of SU-8 were microfabricated on microscope glass coverslips sputtered with a Ti/Au layer. Upon application, chol-DNA adsorbed to the SU-8 structures from solution, leaving the surrounding gold surface free of chol-DNA. chol-DNA immobilization is complete within 15 min and yields a surface coverage in the range of 20-95 pmol/cm(2), which corresponds to a film density of 10(12)-10(13) molecules/cm(2). chol-DNA immobilization is stable and can be sustained despite rinsing, drying, dry storage for several hours, and rehydration of chips. Furthermore, complementary DNA in solution hybridizes efficiently to immobilized chol-DNA.
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| 10. |
- Gözen, Irep, 1980, et al.
(author)
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Fractal avalanche ruptures in biological membranes
- 2010
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In: Nature Materials. - 1476-4660 .- 1476-1122. ; 9:11, s. 908-912
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Journal article (peer-reviewed)abstract
- Bilayer membranes envelope cells as well as organelles, and constitute the most ubiquitous biological material found in all branches of the phylogenetic tree. Cell membrane rupture is an important biological process, and substantial rupture rates are found in skeletal and cardiac muscle cells under a mechanical load(1). Rupture can also be induced by processes such as cell death(2), and active cell membrane repair mechanisms are essential to preserve cell integrity(3). Pore formation in cell membranes is also at the heart of many biomedical applications such as in drug, gene and short interfering RNA delivery(4). Membrane rupture dynamics has been studied in bilayer vesicles under tensile stress(5-8), which consistently produce circular pores(5,6). We observed very different rupture mechanics in bilayer membranes spreading on solid supports: in one instance fingering instabilities were seen resulting in floral-like pores and in another, the rupture proceeded in a series of rapid avalanches causing fractal membrane fragmentation. The intermittent character of rupture evolution and the broad distribution in avalanche sizes is consistent with crackling-noise dynamics(9). Such noisy dynamics appear in fracture of solid disordered materials(10), in dislocation avalanches in plastic deformations(11) and domain wall magnetization avalanches(12). We also observed similar fractal rupture mechanics in spreading cell membranes.
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| 11. |
- Hannestad, Jonas, 1981, et al.
(author)
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Kinetics of Diffusion-Mediated DNA Hybridization in Lipid Monolayer Films Determined by Single-Molecule Fluorescence Spectroscopy
- 2013
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 7:1, s. 308-315
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Journal article (peer-reviewed)abstract
- We use single-molecule fluorescence microscopy to monitor individual hybridization reactions between membrane-anchored DNA strands, occurring in nanofluidic lipid monolayer films deposited on Teflon AF substrates. The DNA molecules are labeled with different fluorescent dyes, which make it possible to simultaneously monitor the movements of two different molecular species, thus enabling tracking of both reactants and products. We employ lattice diffusion simulations to determine reaction probabilities upon interaction. The observed hybridization rate of the 40-mer DNA was more than 2-fold higher than that of the 20-mer DNA. Since the lateral diffusion coefficient of the two different constructs is nearly identical, the effective molecule radius determines the overall kinetics. This implies that when two DNA molecules approach each other, hydrogen bonding takes place distal from the place where the DNA is anchored to the surface. Strand closure then propagates bidirectionally through a zipper-like mechanism, eventually bringing the lipid anchors together. Comparison with hybridization rates for corresponding DNA sequences in solution reveals that hybridization rates are lower for the lipid-anchored strands and that the dependence on strand length is stronger.
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| 12. |
- Jesorka, Aldo, 1967, et al.
(author)
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Controlling Chemistry in Dynamic Nanoscale Systems
- 2010
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In: Springer Series in Chemical Physics. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0172-6218. - 9783642025969 ; 96, s. 449-468
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Conference paper (other academic/artistic)abstract
- The biological cell, the fundamental building block of the living world, is a complex maze of compartmentalized biochemical reactors that embed tens of thousands of chemical reactions running in parallel. Several, if not all, reactors are systematically interconnected by a web of nanofluidic transporters, such as nanotubes, vesicles, and membrane pores with ever-changing shapes and structures [1]. To initiate, terminate, or control chemical reactions, small-scale poly-/pleiomorphic systems undergo rapid and violent shape changes with energy barriers close to kBT , where, due to the small dimensions, diffusional mixing of reactants is rapid. The geometry, i.e. volume, and shape changes can be utilized to control both kinetic and thermodynamic properties of the system. This is in sharp contrast to the man-made macroscopic bioreactors, in which mixing of reactants is aided by mechanical means, such as stirring or sonication, under the assumption that reactions take place in volumes that do not change over time. Such reaction volumes are compact, like a sphere, a cube, or a cylinder, and do not provide for variation of shape. Ordinarily, reaction rates, mechanisms, and thermodynamic properties of chemical reactions in condensed media are based on these assumptions. A number of important questions and challenges arise from these facts. For example, how will we achieve fundamental understanding of how reactor shape affects chemistry on the nanoscale, how do we develop appropriate and powerful experimental model systems, and last but not least what impact will this knowledge have on the design and function of nanotechnological devices with new operation modes derived from natural principles.
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