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3-D Bionanocomposite Surfaces and Interfaces: Fabrication and Characterization Neeraj Kohli, Sachin Vaidya, Robert Ofol PowerPoint Presentation
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RESULTS AND DISCUSSION Fig. 2 shows multiple levels of structural order within micropatterned arrays of cross-linkable, amphiphilic, dendrimer multilayers. The microcontact printing method allowed the film thickness of the nanostructured dendrimer arrays to be controlled. (a) (b)

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3-D Bionanocomposite Surfaces and Interfaces: Fabrication and Characterization Neeraj Kohli, Sachin Vaidya, Robert Ofol


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RESULTS AND DISCUSSION

  • Fig. 2 shows multiple levels of structural order within micropatterned arrays of cross-linkable, amphiphilic, dendrimer multilayers.
  • The microcontact printing method allowed the film thickness of the nanostructured dendrimer arrays to be controlled.

(a)

(b)

Figure 1.Schematic representation of (a) architectural skeleton of a generation two dendrimer; (b) PAMAMOS-DMOMS dendrimer.

Figure 2.Schematic representation of multiple levels of structural order within micropatterned arrays.

3-D Bionanocomposite Surfaces and Interfaces: Fabrication and Characterization Neeraj Kohli, Sachin Vaidya, Robert Ofoli, Mark Worden and Ilsoon Lee

Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan

  • INTRODUCTION
  • Interfaces having 3-D structure and nanometer feature sizes can be produced without photolithography in a multistep process:
    • Microcontact printing (µCP) to deposit a pattern on the surface.
    • Selective, layer-by-layer deposition of polyelectrolytes, biomolecules, etc. onto either the patterned regions or the background regions.
  • Selective deposition is difficult when there is insufficient chemical contrast between the patterned regions and background regions.
    • Amphiphilic molecules (e.g., proteins and some dendrimers) adsorb both to hydrophilic and hydrophobic regions.
    • Polyelectrolyte multilayers adsorb to positive and negative regions.
  • This poster describes
    • Use of µCP to deposit stable patterns of amphiphilic, cross-linkable poly-(amidoamine-organosilicon) (PAMAMOS) dendrimers.
    • Use of µCP to deposit pre-formed, patterned, bionanocomposite interfaces containing alternating layers of polyelectrolytes and amphiphilic biomolecules.

MATERIALS AND METHODS

PAMAM and PAMAMOS Dendrimers

Cross-linking Reaction

  • Radially layered poly-(amidoamine-organosilicon) (PAMAMOS) dendrimers (see Fig. 1a) are versatile, amphiphilic, cross-linkable globular macromolecules.
  • PAMAMOS dendrimers having dimethoxymethylsilyl (DMOMS) end-groups (see Fig. 1b) can be denoted as PAMAMOS-DMOMS.
  • Interdendrimer crosslinking via siloxane condensation (see Fig. 3) stabilizes the 3-D amphiphilic and multilayered structures for a long time.
  • Potential applications:
    • encapsulate nanoparticles
    • molecular templates for chemical and physical modifications in opto-electronic and biomimetic interface applications.

Microcontact Printing Method

  • Stable, nanostructured, amphiphilic and cross-linkable PAMAMOS-DMOMS dendrimer multilayers were micropatterned through
    • Spin-inking and dip-inking onto PDMS stamps.
    • Microcontact printing from stamps onto silicon wafers, glass surfaces, and polyelectrolyte multilayers.

(a)

(b)

Figure 3.(a) Crosslinking of PAMAMOS-DMOMS dendrimers into a covalently bonded network structure. (b) Covalent bonding of PAMAMOS-DMOMS dendrimers to glass surfaces having silanol surface groups.

slide2

chopper

Stamp

Stamp

Stamp

Stamp

Stamp

Stamp

Stamp spin

Stamp spin

Stamp spin

Stamp spin

-

-

-

-

coated with

coated with

coated with

coated with

protein and dendrimers

protein and dendrimers

protein and dendrimers

protein and dendrimers

(b)

(b)

(b)

Growth of

Growth of

Growth of

Growth of

Growth of

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Multilayers

Multilayers

Multilayers

Multilayers

Multilayers

(c)

(c)

(c)

Transfer to a

Transfer to a

Transfer to a

Transfer to a

Transfer to a

substrate

substrate

substrate

substrate

substrate

Protein

Protein

Protein

Protein

Protein

Protein

Dendrimer

Dendrimer

Dendrimer

Dendrimer

Dendrimer

Dendrimer

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Polyelectrolyte

Multilayers

Multilayers

Multilayers

Multilayers

Multilayers

Multilayers

TIRFM Setup

Patterns on a substrate

Patterns on a substrate

Patterns on a substrate

Patterns on a substrate

Patterns on a substrate

(d)

(d)

(d)

(a)

(a)

(a)

(a)

(a)

230nm

90nm

15µm

20µm

Deposition of Pre-Formed, Multilayered Patterns

Pattern Resolution from Directed Self Assembly vs. Deposition of Pre-Formed, Multilayered Patterns

  • Fig. 4 shows a novel method to produce patterned, 3-D bionanocomposites.
  • Multilayered patterns containing dendrimers and proteins are pre-assembled on a PDMS stamp, then deposited onto the substrate.
  • Slight modifications of this approach can result in many different 3-D architectures (See Figure 4 b-d).
  • Fig 6 shows that deposition of pre-formed, multilayered patterns (b) gives higher resolution than directed self assembly (a).

(a)

(b)

Growth of

Figure 6. (a) Arrays of proteins obtained using directed self assembly (b) Arrays of proteins obtained using the novel approach

Polyelectrolyte

Multilayers

Total Internal Reflection Fluorescence Microscopy

  • Shallow evanescent wave depth (80nm) allows for selective surface illumination and rejection of bulk contribution.
  • Monitors adsorption of macromolecules (proteins, polymers, etc.) onto functionalized surfaces.

Transfer to a

substrate

Protein

Protein

Dendrimer

Dendrimer

Polyelectrolyte

Polyelectrolyte

Multilayers

Multilayers

Patterns on a substrate

Figure 4. (a) Schematic representation of the procedure used for printing. (b-d) Some examples of the different 3-D structures possible using this technique.

Optical Microscopy and Atomic Force Microscopy

Adsorption of

Tagged Liposomes

onto PDAC Surface

  • Fluorescence microscopy was used to verify the alternating protein and dendrimer layers in the bionanocomposite films.
    • In Fig. 5a, only the protein was fluorescently labeled.
    • In Fig. 5b, only the dendrimer was fluorescently labeled.
  • AFM was used to verify incorporation of PEM bilayers into the films. Figs. 5c and 5d show peak height increase due to addition of 50 PEM bilayers.

REFERENCES

  • Park, J.; Hammond, P. T. ”Multilayer Transfer Printing for Polyelectrolyte Multilayer Patterning: Direct Transfer of Layer-by-Layer Assembled Micropatterned Thin Films”, Adv. Mater. 16, 520 (2004).
  • Lee, I.; Ahn, J. S.; Hendricks, T.; Rubner, M. F.; Hammond, P. T. "Patterned and Controlled Polyelectrolyte Fractal Growth and Aggregations," Langmuir20, 2478-2483 (2004).
  • Lee, I.; Hammond, P. T.; Rubner, M. F. "Selective Electroless Nickel Plating of Particle Arrays on Polyelectrolyte Multilayers," Chem. Mater.15, 4583-4589, (2003).
  • Kidambi, S.; Chan, C.; Lee, I. "Selective Depositions on Polyelectrolyte Multilayers: Self-Assembled Monolayers of m-dPEG Acid as Molecular Templates," J. Am. Chem. Soc. In press, (2004).
  • Kohli, N.; Dvornic, P.; Kaganove, S.; Worden, M.; Lee, I.” Nanostructured Cross-linkable Micropatterns via Amphiphilic Dendrimer Stamping”, Macromolecular Rapid Communications, in press, (2004).
  • Kohli, N.; Worden, M.; Lee, I.” Fabrication of Three Dimensional and Layered Bionanocomposite Arrays" (submitted).

(a)

(b)

ACKNOWLEDGMENTS

Authors thank Drs. Kaganove and Dvornic at the Michigan Molecular Institute (MMI) for the discussion on the various dendrimer chemistries. This work was funded by the Michigan State University (MSU) Start-Up Funds, the MSU Intramural Research Grants Program, and the Seed Research Fund by the Center for Fundamental Materials Research at MSU.

(c)

(d)

Figure 5. (a) Fluorescence image of the patterned films of protein, dendrimer and PEMs with fluorescently labeled protein as the topmost layer. (b) Fluorescence image of the line patterns of fluorescently labeled dendrimers sandwiched between patterned proteins and PEMs. (c) AFM image of patterned film of protein and dendrimers deposited onto PEM-coated substrate, with protein as the topmost layer. (d) AFM image of patterned film of protein, dendrimers, and PEMs (50 bilayers), with protein as the topmost layer