Engineering Gradient Biomaterials for Controlled Signaling during Stem Cell Differentiation

1. Engineering Gradient Biomaterials for Controlled Signaling during Stem Cell Differentiation Miguel Benson Kristin Riching Kristen Sipsma Kelly Toy

2. University of Wisconsin - MadisonBiomedical Engineering Design Courses INTELLECTUAL PROPERTY STATEMENT All information provided by individuals or Design Project Groups during this or subsequent presentations is the property of the researchers presenting this information. In addition, any information provided herein may include results sponsored by and provided to a member company of the Biomedical Engineering Student Design Consortium (SDC). Anyone to whom this information is disclosed: 1) Agrees to use this information solely for purposes related to this review; 2) Agrees not to use this information for any other purpose unless given written approval in advance by the Project Group, the Client / SDC, and the Advisor. 3) Agrees to keep this information in confidence until the relevant parties listed in Part (2) above have evaluated and secured any applicable intellectual property rights in this information. 4) Continued attendance at this presentation constitutes compliance with this agreement.

3. Client Brian Peret, Graduate Student, Dept. of Biomedical Engineering William Murphy, Assistant Professor, Dept. of Biomedical Engineering

4. Problem Statement/Motivation Design a mechanism by which a protein gradient within a hydrogel can be established and controlled Control of gradients and concentration of growth factors will facilitate the understanding of stem cell differentiation

5. Design Requirements/Assumptions Medium must allow diffusion of proteins Source must not deplete during desired time frame Release of proteins from source is linear Reasonable time frame of diffusion Changing parameters need to give results predictive of actual diffusion patterns Make computer simulation

6. Biological Rationale

7. Hydrogel Polymer or copolymer infused with water Hydrophilic Swells when in contact with water Cross linking of polymer counteracts swelling force UV cross linking Diffusivity Cross linking Degree of swelling Molecular weight

8. Microspheres Encapsulate protein or growth factor Allow timed release of contents Biodegradable Biocompatible Contents released through both diffusion and breakdown of microsphere Poly(lactide-co-glycolide) Most widely used for biological applications Composition affects rate of breakdown

9. Diffusion through Permeable Barrier Non-encapsulated proteins placed into section of hydrogel Porous barrier allows for time controlled continuous diffusion

10. Analysis of Design 1 Advantage Barrier creates constant rate of diffusion Disadvantages Source of proteins will deplete Equilibrium will be reached

11. Diffusion from Planar Source of Microspheres Even distribution of microspheres along one edge of rectangular hydrogel Constant protein release from microsphere Protein diffuses through hydrogel Assume diffusion is one direction

12. Analysis of Design 2 Advantages Simplified equations of diffusion Constant source concentration Allows greater control of release rate and initial concentration Disadvantages Possible conformational change of some proteins during microsphere preparation

13. Diffusion from Point Source of Microspheres Microspheres located at a single point in center of hydrogel Causes radial diffusion

14. Analysis of Design 3 Advantages Proteins move out into a wider area Disadvantages Two dimensional movement of proteins Microspheres must be extremely small Difficult to measure gradient

15. Design Matrix

16. Future Work Determine relationships between: Diffusivity and molecular weight of hydrogel polymer Diffusivity and cross linking density Concentration and distance from source Create computer simulation model Test using appropriate hydrogel and microspheres with fluorescent tags

17. Questions?