Nanomechanics of Biological, Biomedical, Biomimetic Materials

1. Nanomechanics of Biological, Biomedical, Biomimetic Materials Christine Ortiz, MIT-DMSE 2004 (http://web.mit.edu/cortiz/www) I. BIOLOGICAL TISSUES ●Cartilage (J. Seog, L. Han, L. Ng, D. Dean) ● Bone (K. Tai) ●Nacre (B. Bruet, C. King, H. Qi, R. Panas) III. BIOMIMETIC BLOCK COPOLYMERS ●Non Stimulus Responsive P(HEMA-g-EG) (D. Zhang) ●Stimulus Responsive p(MAA-g-EG) (M. Ye) II. BIOMEDICAL INTERACTIONS ●Protein-SAMs/PEO (M. Rixman) ●Vascular Grafts (C. Macias) ●Saccharide Surfaces (J. Choi, N. Yang) ●Endotracheal Tubes (K. Brodie) ●Pharmaceuticals (R. Domike) ●Bone Implants (J. Vandiver)

2. Molecular Origins of Bio(hemo)compatibility : Materials Design Issues and Challenges at the Nanoscale CHRISTINE ORTIZ, Assistant Professor Monica Rixman, Delphine Dean, Celia Macias Department of Materials Science and Engineering, MIT WWW : http://web.mit.edu/cortiz/www c D. Breger, used w/permission, http://www.ldeo.columbia.edu/micro/images.section/pages/bloodclot.html

3. FACTORS AFFECTING PROTEIN ADSORPTION 227th ACS National Meeting Division of Polymer Chemistry Symposium "Biomacromolecule Interactions with Synthetic Surfaces" Anaheim, CA 2004. U=-∫F(D)dD Initial protein adsorption will be determined by longer range, larger spatial length scale of averaged surface properties : many different attractive/ repulsive components lead to complicated interactions (Szleifer, I., 1997, Halperin, A., 1999 Leckband, D., et al., 2000)  Secondary stages of protein adsorption depend on shorter range biomolecular adhesive binding processes that take place when the protein is in close contact with the surface (*the conformation, orientation, and mobility of the adsorbed proteins, the time scale of conformational changes, protein exchange and desorption, and interactions of adsorbed proteins with each other) D SURFACE COATING BIOMATERIAL CHRISTINE ORTIZ, ASSISTANT PROFESSOR MASSACHUSETTS INSTITUTE OF TECHNOLOGY DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING CAMBRIDGE, MA 02139

4. Direct Measurement of Protein Interactions with End-Grafted Poly(ethylene oxide) (PEO) Macromolecules 227th ACS National Meeting Division of Polymer Chemistry Symposium "Biomacromolecule Interactions with Synthetic Surfaces" Anaheim, CA 2004. Rixman, et al. accepted, Langmuir 2003. lipid-bound HSA functionalized probe tip, RTIP~65 nm (SEM) F Si3N4 sodium phosphate buffer solution IS=0.01M pH=7.4 ~35-190 proteins in maximum interaction area (D=0) covalently immobilized HSA ~10 nm chemically end-grafted PEO50K “mushroom” Lcontour= 393 nm RF=8.7 nm D ~2.5 PEO chains in maximum interaction area (D=0) Au-coated silicon chip CHRISTINE ORTIZ, ASSISTANT PROFESSOR MASSACHUSETTS INSTITUTE OF TECHNOLOGY DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING CAMBRIDGE, MA 02139 s = 62 ± 28 nm

5. Chemical Attachment Scheme of Lipid-Bound HSA to Si3N4 Probe Tip A. Vinkier; Heyvaert, I.; D'Hoore, A.; McKittrick, T.; C., V. H.; Engelborghs, Y.; Hellemans, I. Ultramicroscopy1995, 57, 337. S. O. Vansteenkiste; Corneillie, S. I.; Schacht, E. H.; Chen, X.; Davies, M. C.; Moens, M.; Van Vaeck, L. Langmuir2000, 16, 3330. probe tip location Fluorescence micrograph of HSA-functionalized cantilever (courtesy of Irvine Lab-DMSE)

6. AVERAGE APPROACH CURVE : HSA PROBE TIP VERSUS PEO (SUBTRACTED AU INTERACTION) PBS, IS=0.01M, pH=7.4 F RF (PEO) Au • magnitude of force much larger than predicted by theory Rixman, et al., Langmuir 2003.

7. HSA versus PEO : Effect of NaCl IS Approach ● NaCl reduces the goodness of solvent for PEO (Armstrong, et al. 2001) : configurational entropy force expected↓ with ↑IS ● Salt screening : electrostatic double layer force expected↓ with ↑IS CONCLUSION: Electrostatic double layer and configurational entropy are outweighed by another interaction which increases with IS →possibly due to water interphase layer RF (PEO) Rixman, et al. 2003 unpublished data

8. HSA versus PEO : Effect of Solvent on Approach Isopropanol has been shown to block hydrophobic interaction forces (Jiang, et al 2002) RF (PEO) Rixman, et al. 2003 unpublished data

9. ACKNOWLEDGEMENTS 50th Annual Meeting of the Orthopaedic Research Society (San Francisco, CA) Workshop on Molecular Nano-Mechanics of Extracellular Matrix of Musculoskeletal Tissues Prof. Alan Grodzinsky Delphine Dean Joonil Seog Laurel Ng Kuangshin Tai Outside Collaborators:Dr. Anna Plaas, Shirley Wong-Palms (Shriners) Funding: Dupont-MIT Alliance, Shriners of North America, NIH AR45779 (AJG), Whitaker Foundation, Cambridge-MIT Institute CHRISTINE ORTIZ, ASSISTANT PROFESSOR MASSACHUSETTS INSTITUTE OF TECHNOLOGY DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING CAMBRIDGE, MA 02139