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. 2010 May 18;22(19):2142-7.
doi: 10.1002/adma.200903625.

Particle/Fluid interface replication as a means of producing topographically patterned polydimethylsiloxane surfaces for deposition of lipid bilayers

Anand Bala Subramaniam  1 , Sigolene Lecuyer, Kumaran S Ramamurthi, Richard Losick, Howard A Stone
Affiliations

Particle/Fluid interface replication as a means of producing topographically patterned polydimethylsiloxane surfaces for deposition of lipid bilayers

Anand Bala Subramaniam et al. Adv Mater. .
No abstract available

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Figures

Figure 1
Figure 1
Schematic of the fabrication procedure. a) Colloidal particles are spread on an air-water interface, then PDMS is poured on the surface and cured. b) The colloidal particles are now embedded in the solid PDMS. The surface serves as a template, and a UV curable epoxy is used to make a mold of the particle-studded surface. To obtain negatively curved features, polystyrene particles are used and are dissolved with DMSO before making the epoxy mold. c) PDMS is poured into the mold and cured to obtain d) an all PDMS topographically patterned substrate.
Figure 2
Figure 2
Examples of topographically patterned PDMS substrates. a–d, g, h) SEM images. a,b) Both surfaces fabricated with 2.37 μm radius silica particles as template particles. Silica particles in (a) were treated with chloro(dodecyl)dimethylsilane which makes them very hydrophobic (contact angle 165°). Template particles in (b) were treated with chlorotrimethysilane. The shorter carbon chain produces a less hydrophobic particle which leads to a smaller contact angle and thus larger feature height. Features on both surfaces have the same mean and Gaussian curvatures which are set by the radius of the template particle. c) Features with negative mean curvature and positive Gaussian curvature fabricated using 800 nm radius polystyrene particles. d) Surface with features of both positive and negative mean curvatures. The planar regions in between the features have zero mean curvature. Thus all three possible signs of curvature are present on this surface. (e, f) AFM amplitude trace of surfaces fabricated with rod-shaped bacterial cells as template particles e) Surface with negative mean curvature features which are replicas of B.subtilis. f) A zoomed in scan of a positive mean curvature replica of B.subtilis. Unidentified extracellular material is also reproduced by the casting process. The sign of the Gaussian curvature changes along the shape as discussed in the text. g) Surfaces with negative mean curvature cylindrical features fabricated by replicating multi-walled carbon nanotubes h) Positive mean curvature cylindrical features which are replicas of carbon nanotubes. a–d) Scale bar 2 μm. e, f, g) Scale bar 1 μm. h) Scale bar 500 nm
Figure 3
Figure 3
Confocal images of lipid bilayer covered substrates. a) Transmitted light image of 1.28 μm radius positively curved features. b) Z-projection using the sum slices method. c) Transmitted light image of B. subtilis features d) Z-projection using the sum slices method, intensity is uniform throughout the bilayer except for bright points where unfused small vesicles remain adsorbed to the bilayer. Normalized line intensity profile for the spherical features (inset shows line chosen) through: e) the transmitted light image, where the centers of the features appear as intensity maxima. f) rhodamine-DPPE labeled bilayer, showing, as expected, that bilayer fluorescence intensity does not correlate with the position of the underlying features. An orthogonal section through the bilayer demonstrates the topographical patterning. Scale bars 2 μm.
Figure 4
Figure 4
Curvature-modulated phase separation in a supported lipid bilayer, demonstrated on a PDMS substrate with positively curved features with radius of curvature of 500 nm: a) Fluorescence image of the upper bilayer composed of DPPC/DOPC/cholesterol/DOTAP mixture labeled with 0.5 mol percent rhodamine-DPPE, below the miscibility transition temperature. The rhodamine-DPPE segregates to the cholesterol poor Ld phase which appears as bright domains while the cholesterol rich Lo phase appears dark. The edge of the bilayer patch can be seen as the curved line at bottom left of the image. b) Fluorescence image of the lower DMPC/NBD-PC bilayer. c) Transmitted light image of the underlying substrate d) Superimposed image of the upper bilayer and the transmitted light image. Scale bar 1μm. e–f) Normalized line intensity profile (inset shows line chosen) through: e) Upper bilayer. f) Lower bilayer. Maxima in rhodamine intensity corresponds to a minima in NBD intensity, due to Förster resonance energy transfer (FRET) between the NBD from the lower bilayer and the rhodamine in the upper bilayer.[7] g) Transmitted light image of the substrate. The centers of the features appear as intensity maxima. The vertical lines are guides to the eye showing that maxima in upper bilayer intensity correspond to the centers of the curved features. It is clear that the Ld phase preferentially localizes to the positively curved features.
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