Surface Micro- and Nanopatterning: Novel SMAP Technique to Produce Adhesive Patterns in a Non-Adhesive Background or Hydrophilic/Hydrophobic Patterns. Model Surfaces to Study Cell-Surface Interactions

Background:

The project goal is the development of a new chemical patterning technique for biological applications into the nanometer range. Selective Molecular Assembly Patterning (SMAP) is based on photolithographic processes to create patterned SiO₂/TiO₂ substrates and subsequently selectively adsorb protein and cell adhesive and resistant organic molecules. Since not the organic molecules are patterned, but the metal oxide substrates, it bears the advantage of contaminant free patterned surfaces in nanometer range across large areas.

Materials and Methods:

Standard photolithography was used to create patterns of titanium oxide within a matrix of silicon oxide. Using the fact that ordered SAMs of alkane phosphates form on the TiO₂, but not on the SiO₂, surfaces, by self-assembly from aqueous solutions, the TiO₂ structures were rendered hydrophobic and hence protein-adsorbing. Poly-L-lysine-g-poly(ethylene glycol) (PLL-g-PEG)3,4 was used to render the exposed SiO₂ protein-resistant, thus creating a contrast with respect to protein adsorption. X-ray photoelectron spectroscopy and imaging time-of-flight secondary ion mass spectrometry were used to characterize the surfaces in vacuo, while fluorescence microscopy (Figure 1A) was used for studies in aqueous media.

Results:

Quantitative XPS as well as qualitative ToF-SIMS results proved that dodecylphosphate (DDP) adsorbed on the TiO₂ surface forming a self-assembled monolayer5, leaving SiO₂ bare. Subsequent modification with PLL-g-PEG resulted in protein-adhesive patches (TiO₂/DDP) in a matrix resistant to protein adsorption (SiO₂/PLL-g-PEG), as shown in Figure 1A. Human foreskin fibroblasts (HFF) as well as smooth muscle cells (SMC), incubated with such substrates in serum, exhibited clear preference towards attaching to the protein-adhesive (hydrophobic) areas (Figure 1B), where they form focal contacts.
First paper on SMAP

References:

• (1) Wheeler et al.(1999) J Biomech Eng 121:73-78.
• (2) Chen et al. (1997) Science 276: 1425-1428.
• (3) Elbert and Hubbell (1998), Chem Biol 5:177-83.
• (4) Kenausis et al. (2000) J Phys Chem B 104:3298-3309.
• (5) Textor et al. (2000) Langmuir 16:3257-3271.
• (6) Selective Molecular Assembly Patterning: A New Approach to Micro- and Nanochemical Patterning of Surfaces for Biological Applications, R. Michel, J.W. Lussi, G. Csúcs, I. Reviakine, G. Danuser, B. Ketterer, J.A. Hubbell, M. Textor, N.D. Spencer, Langmuir 18(8): 3281-3287 (2002).
• (7) A Novel Approach to Produce Biologically Relevant Chemical Patterns at the Nanometer Scale: Selective Molecular Assembly Patterning Combined With Colloidal Lithography, R. Michel, I. Reviakine, D. Sutherland, Ch. Fokas, G. Csucs, G. Danuser, N.D. Spencer and M. Textor, Langmuir 18(22): 8580-8586 (2002).

Contact:

• Didier Falconnet
• Jost W. Lussi
• Marcus Textor