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Fabrication of Novel Biomaterials

Fabrication of Novel Biomaterials. for Peripheral Nerve Tissue. Engineering Strategies. Archit Sanghvi, David Silva, Kiley Miller, Julie Williams,. Angela Belcher, Christine Schmidt. Motivation.

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Fabrication of Novel Biomaterials

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  1. Fabrication of Novel Biomaterials

  2. for Peripheral Nerve Tissue

  3. Engineering Strategies

  4. Archit Sanghvi, David Silva, Kiley Miller, Julie Williams,

  5. Angela Belcher, Christine Schmidt

  6. Motivation • A key goal in the design of new polymeric biomaterials for biomedical and drug delivery applications is to specifically control the interactions of biomolecules and living cells with biomaterial surfaces • Our major focus is on the development of materials to promote the regeneration of damaged nerves and to overcome drawbacks with the current clinical use of nerve grafts • Use of normal donor nerve from an uninjured body location (autograft) is limited by tissue availability, the need for multiple surgical procedures, and loss of function at the donor site • One possible alternative would be to develop engineered constructs to replace those elements necessary for axonal proliferation, including support cells (i.e., Schwann cells), growth factors, scaffolding material, and matrix proteins

  7. Use of Synthetic Biomaterials • Two key criteria of any implanted biomedical device include: biocompatibility with the body and ability of material to function physically in desired capacity • The ability to design, fabricate, and optimize surfaces tailored for tissue engineering application is crucial for synthesizing biocompatible materials • One of the more difficult problems in bioengineering science is to reproduce the properties and functionality of human tissues and organs using artificial biomaterials

  8. Project Goals (1) Physical modification of biomaterials • Construct 3D biologically active polymer-based nerve guidance channels (NGCs) for nerve repair application • Design nerve conduits with micron-scale precision (spatial control) to enhance cellular interactions with synthetic materials (2) Chemical modification of biomaterials • Fabricate polymer-based synthetic materials to mimic natural cellular microenvironments (biomimetics) • Develop ligand-based surface modifications onto biodegradable polymer surfaces

  9. Physical Modification3D Nerve Conduit Fabrication (Microfab Inc.) Y-shaped bifurcated conduit 100 mm optical polymer waveguide splitter; pattern representative of a bifurcated pathway MediLabTM ink-jet based Tissue Engineering Platform

  10. Cells adhere to and are viable on Microfab Surface 10x 10x 24 hr study illustrating cell viability using live/dead assay (green-live, red-dead) 10x 10x 72 hr study illustrating cell viability using live/dead assay (green-live, red-dead Cells: PC12 (rat adrenal tumor cells) neuron-like cells used in study Material: Copolymer of poly-lactic acid (PLA) and poly-ethylene glycol (PEG)

  11. Quantitative Data Illustrating PC12 Cell Adhesion on Microfab Polymer *Control: Cells were plated on the same surface area using plexiglass wells on polystyrene TC dishes Conclusion: Results showed excellent potential for NGC development using Microfab polymer, because in vitro studies demonstrated comparable PC12 adhesion and viability

  12. Surface Engineering of Microfab Polymer SEM of Microfab polymer (PLA-PEG) on glass slide, illustrating precise-control fabrication Biotin moieties presented at the polymer surface are used to immobilize tetrameric avidin molecules. Free biotin binding sites on the avidin molecules are in turn used to anchor biotinylated ligands such as, bNGF.

  13. Chemical ModificationSelection of Peptides with Polymer Binding Specificity • Specific Objective • Current techniques to modify material surfaces are difficult due to limited selectivity for binding non-biological surfaces • A unique “biopanning” method (described below) would be used to select for specific peptides that bind to a range of non-biological materials with high specificity, resulting in direct fabrication of modified materials • Potential Applications • Nerve Regeneration: Chemical modification of biomaterials to enhance neuron-specific interactions • Electronics: Use in electronic devices to control placement and assembly to direct nanoscale fabrication (‘bottom-up’ approach) • Drug-delivery: Site-specific delivery via controlled peptide-polymeric vehicle interaction

  14. Determining Peptide-Libraries via “Biopanning” Technique • A library containing ~109 unique phage-displayed peptide combinations is incubated with the polymer of interest (target) • Unbound phage are washed away, eluting the specifically-bound phage • Eluted phage are amplified and taken through additional cycles of panning/amplification to enrich the pool of phage in favor of the tightest binding sequences • After 3-4 rounds, individual clones are isolated and sequenced • We are currently researching specific-peptide sequences for two biomaterials: polypyrrole (PP) and poly-lactic-coglycolic acid (PLGA) Step 1 Step 2 Step 3

  15. Future Work • Incorporation of biotinylated bNGF on PLA-biotinylated-PEG via avidin • Effects of neurotrophic factor (i.e., bNGF) gradient on surface-modified Microfab polymer system with PC12 cells • Determining specific-peptide libraries for PP and PLGA to modify polymers for ligand placement

  16. Acknowledgements • National Institutes of Health (NIH) SBIR Grant • Microfab Technologies Inc. • Michael Grove (Chemist, Microfab Inc.) • Dr. Angela Belcher’s Lab • Texas Materials Institute (TMI)

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