| 1. |
- Ainla, Alar, 1982, et al.
(författare)
-
A Microfluidic Diluter Based on Pulse Width Flow Modulation
- 2009
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 81:13, s. 5549-5556
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that pulse width flow modulation (PWFM) can be used to design fasts accurate, and precise multi-stage dilution modules for microfluidic devices. The PWFM stage unit presented here yields 10-fold dilution, but several PWFM stages can be connected in series to yield higher-order dilutions. We have combined two stages in a device thus capable of diluting up to 100-fold, and we have experimentally determined a set of rules that can be conveniently utilized to design multistage diluters. Microfabrication with resist-based molds yielded geometrical channel height variances of 7% (22.9(16) mu m) with corresponding hydraulic resistance variances of similar to 20%. Pulsing frequencies, channel lengths, and flow pressures can be chosen within a wide range to establish the desired diluter properties. Finally, we illustrate the benefits of on-chip dilution in an example application where we investigate the effect of the Ca2+ concentration on a phospholipid bilayer spreading from a membrane reservoir onto a SiO2 surface. This is one of many possible applications where flexible concentration control is desirable.
|
|
| 2. |
- Benkoski, Jason J., 1975, et al.
(författare)
-
Light-Regulated release of liposomes from phospholipid membranes via photoresponsive polymer-DNA conjugates
- 2006
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 2:8, s. 710-715
-
Tidskriftsartikel (refereegranskat)abstract
- A method for releasing tethered liposomes from a supported lipid bilayer in response to a light stimulus is described. The tethering is accomplished through the hybridization of end-functionalized DNA that resides on both the supported lipid bilayer and liposome surfaces. Normally consisting of cholesterol or lipid tails, the end group is replaced in this study by a photoresponsive polymer that partitions into lipid bilayers at physiological pH. When exposed to UV light, it undergoes excited state proton transfer with water. The ensuing increase in polarity increases the solubility of the polymer in the aqueous phase. Quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence microscopy have been used to record both the construction of the vesicle assembly and the subsequent response to UV light. It is found that the critical flow rate for vesicle release is reduced when buffer flow is performed in conjunction with UV exposure. © The Royal Society of Chemistry 2006.
|
|
| 3. |
- Bridle, Helen, 1979, et al.
(författare)
-
On-chip fabrication to add temperature control to a microfluidic solution exchange system
- 2008
-
Ingår i: Lab on a Chip - Miniaturisation for Chemistry and Biology. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 8:3, s. 480-483
-
Tidskriftsartikel (refereegranskat)abstract
- We present a concept for the post production modification of commercially available microfluidic devices to incorporate local temperature control, thus allowing for the exact alignment of heating structures with the existing features, e.g. wells, channels or valves, of a system. Specifically, we demonstrate the application of programmable local heating, controlled by computerized PI regulation, to a rapid solution exchanger. Characterisation of the system to show that both uniform temperature distributions and temperature gradients can be established, and to confirm that the solution exchange properties are undisturbed by heating, was achieved using in situ thermometry and amperometry. © The Royal Society of Chemistry.
|
|
| 4. |
- Czolkos, Ilja, 1980, et al.
(författare)
-
Controlled formation and mixing of two-dimensional fluids
- 2007
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 7:7, s. 1980-1984
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Czolkos, Ilja, 1980, et al.
(författare)
-
Platform for Controlled Supramolecular Nano-Assembly
- 2009
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 9:6, s. 2482-2486
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
|
|
| 7. |
- Erkan, Yavuz, 1982, et al.
(författare)
-
Direct immobilization of cholesteryl-TEG-modified oligonucleotides onto hydrophobic SU-8 surfaces
- 2007
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 23:10, s. 5259-5263
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Jesorka, Aldo, 1967, et al.
(författare)
-
COMPLEX NANOTUBE-LIPOSOME NETWORKS
- 2009
-
Ingår i: Methods in Enzymology. - 1557-7988 .- 0076-6879. ; 464:C, s. 309-325
-
Tidskriftsartikel (refereegranskat)abstract
- Surfactant nanotube-vesicle networks (NVN) belong to the smallest artificial devices known to date for performing controlled chemical operations with enzymes. Newly established means for transport of chemical reactants between containers, as well as advancements in initiation and control of chemical reactions in such systems have opened pathways to new devices with a resolution down to the single-molecule level. Here, we summarize the fabrication and functionalization of complex nanotube-liposome networks for such devices, and discuss related aspects of their application for studying chemical kinetics and materials transport phenomena in ultrasmall-scale bio-mimetic environments.
|
|
| 9. |
- Jesorka, Aldo, 1967, et al.
(författare)
-
Controlling the internal structure of giant unilamellar vesicles by means of reversible temperature dependent sol-gel transition of internalized poly(N-isopropyl acrylamide)
- 2005
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 21:4, s. 1230-1237
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present preparation and basic applications of lipid-bilayer-enclosed picoliter volumes (microcontainers) of solutions of poly(N-isopropylacrylamide) (PNIPAAm). Giant unilamellar vesicles (GUVs) were prepared from phospholipids using a standard swelling procedure and subsequently surface immobilized. Clear, slightly viscous solutions of PNIPAAm of varying concentration in aqueous buffer were directly pressure-microinjected into the GUVs, using a submicrometer-sized, pointed capillary. The GUV was subjected to changing temperature over a 21-40 °C range. The typical phase transition of the polymeric material upon heating and cooling across the lower critical solution temperature was followed using optical microscopy and shown to be reversible over multiple sequential heating/cooling cycles without compromising the integrity of the GUV membrane. Fluorescent, carboxylic acid modified 200 nm latex beads, co-injected with the PNIPAAm solution, were temperature-reversibly immobilized during the phase transition, practically freezing the Brownian motion of the entrapped particles in the volume. Furthermore, a co-injected water soluble fluorescent polysaccharide - dye conjugate was shown not to migrate from the aqueous phase into the hydrophobic polymer part upon heating, whereas the fluorescent beads were completely but reversibly immobilized in the hydrophobic domains of dense polymer agglomerates. The system reported here provides a feasible method for the reversible stabilization and solidification of GUV interior volumes, e.g., as a micrometer-sized model system for controlled drug release.
|
|
| 10. |
- Jesorka, Aldo, 1967, et al.
(författare)
-
Liposomes: Technologies and Analytical Applications
- 2008
-
Ingår i: Annual Review of Analytical Chemistry. - 1936-1327 .- 1936-1335. ; 1, s. 801-832
-
Tidskriftsartikel (refereegranskat)abstract
- Liposomes are structurally and functionally some of the most versatile supramolecular assemblies in existence. Since the beginning of active research on lipid vesicles in 1965, the field has progressed enormously and applications are well established in several areas, such as drug and gene delivery. In the analytical sciences, liposomes serve a dual purpose: Either they are analytes, typically in quality-assessment procedures of liposome preparations, or they are functional components in a variety of new analytical systems. Liposome immunoassays, for example, benefit greatly from the amplification provided by encapsulated markers, and nanotube-interconnected liposome networks have emerged as ultrasmall-scale analytical devices. This review provides information about new developments in some of the most actively researched liposome-related topics
|
|
