NanoNewton
Podcast discussions with scientists and MIT students in the field of Nanomechanics*
in conjunction with the undergraduate engineering course :
3.052 Nanomechanics of Materials and Biomaterials
Your HOST: Christine Ortiz, Associate
Professor
Department of Materials Science and
Engineering, MIT Cambridge, MA
* Nanomechanics is the study of forces, motions, energies, and
deformations over distances of ~ < 100 nanometers or involving forces ~ <
100 nanoNewton. 1 nanoNewton is 10-9 times the force that produces an
acceleration of 1 meter per second per second when exerted on a mass of 1
kilogram.
Topic : Nanomechanics of Cartilage Aggrecan
Recording Date : 12/08/06 12:30pm-1:30pm
Participants :
Alan Grodzinsky (coauthor)
Delphine Dean (lead author, by phone)
Lin Han (coauthor)
Laura Daher (ugrad, Senior, chemistry dept.)
Christine Ortiz (moderator, coauthor)
Notes :
- Please have hardcopy of paper with you to refer to during podcast
- The podcast is meant to be a back and forth informal lively discussion with the students rather than a strict
question-answer interview.
- The podcast will be posted on the internet where you will be able to download the .mp4 file
- Let undergrads talk as much as possible
- The technical level is aimed at the undergrad level for the majority of the podcast, but by the end can be
more advanced to the grad level.
Discussion Topic :
"Compressive Nanomechanics of Opposing Aggrecan Macromolecules," D. Dean, L. Han, A.J. Grodzinsky,
and C. Ortiz, Journal of Biomechanics, 39, 14, 2555-2565, 2006.
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Outline : Questions are meant to be the starting point for discussion.
-Ortiz will introduce Grodzinsky (bio below, maybe not entire bio), then will ask other participants to
introduce themselves. Delphine can mention her background at MIT.
Alan J. Grodzinsky received the B.S. and M.S. in 1971, and the Ph.D. in 1974, all in Electrical Engineering at MIT. He
is currently the Director of MIT's Center for Biomedical Engineering (CBE), and is Professor of Electrical, Mechanical,
and Biological Engineering in the Departments of Electrical Engineering and Computer Science (EECS), Mechanical
Engineering (ME), and Biological Engineering (BE). His research interests include the degeneration and repair of
cartilage in injured and arthritic joints, cellular mechanotransduction, molecular nano-mechanics, cartilage tissue
engineering, and the study of the influence of physical forces on gene expression and matrix biosynthesis in cartilage
and other musculoskeletal connective tissues. His group has also carried out research on nondestructive
spectroscopic detection of early cartilage degeneration and electrically controlled gels for separations, drug delivery,
sensors and actuators. He has published almost 200 journal articles and reviews in these fields of research. He
previously taught through much of the undergraduate core EE curriculum in EECS, and has co-developed two of the
required core graduate courses in the current BE PhD Program. In BE, he is currently the Chair of the Graduate
Program and a member of the department’s Executive Committee. He was co-developer of MIT’s first
interdepartmental minor: that in Biomedical Engineering.
Professor Grodzinsky was elected Founding Fellow of the American Institute of Medical and Biological Engineering.
He is past Chair of the Gordon Research Conference on Musculoskeletal Biology and Bioengineering, past President
of the International Cartilage Repair Society and the Society for Physical Regulation in Medicine and Biology. In 2007
he will become President of the Orthopaedic Research Society (ORS). He has been on the Editorial Boards of the
Journal of Orthopaedic Research, Archives Biochemistry and Biophysics and Polymer Networks and Gels, and is
currently on the Editorial Board of Arthritis and Rheumatism. Dr. Grodzinsky is a recipient of the NIH MERIT Award
for research on Cartilage Metabolic Response to Loading, and other awards including the Melville Medal of the
American Society of Mechanical Engineers (ASME) for the best original paper in all Mechanical Engineering fields,
the Ann Doner Vaughan Kappa Delta Research Prize of the American Academy of Orthopaedic Surgeons (AAOS),
the Borelli Award of the American Society of Biomechanics (ASB), the Kappa Delta Award of the Society For
Physical Regulation in Medicine and Biology, and the ASME Bioengineering Division Best Paper Award. At MIT, he
was recently given the Class of 1960 Innovation in Education Award and the IEEE/ACM Award for Best
Undergraduate Academic Advisor in the EECS Department. He has been on the Science Advisory Boards of Smith
and Nephew, ISTO Technologies, and Tissue Engineering, Inc., and is a founder and Science Advisory Board
Member of 3D-Matrix. He has been a consultant for over 40 industrial and academic institutions, and a consultant to
federal agencies including the NIH, NSF, FDA, and the Department of Justice.
-Alan and Delphine - Can you please define a few basic terms; cartilage, aggrecan, and glycosaminoglycan,
electrostatic double layer.
-Alan- how did you first get interested in the cartilage field? Then, explain motivation for the paper. Can you
please give us some information on cartilage diseases (or the most important one) and the current modes
of treatment.
- Lin and then Delphine- please explain the basic experiment in Figure 1. Explain what a cartilage-mimetic systen is.
What kind of relevant information does the Nanosized tip give? You draw the probe in Figure 1 with 4 aggrecan- how
do you know there are 4 aggrecan on the tip? You have schematics of the aggrecan- do they really like that in
reality?
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- Delphine/Lin - What did you find the most difficult part about the experiment?
- Explain Results : Figure 2. Delphine. Role of electrostatics versus nonelectrostatics. How many experiments for
each force curve, standard deviations, etc. reproducibility
- Lin explain Figure 4/5.
-Christine explain Figure 7b. This seems to a big one of the most significant results- different mechanisms and high
nonlinearly at high strains-stiffens nonlinearly with increasing strain at the molecular level→
mechanism to prevent large strains that could result in permanent deformation, fracture, or tearing.
-Modeling Alan explain models/ advantages and disadvantages.
- Delphine explain modeling results Figure 10.
-Alan, in your opinion why do you think cartilage takes up so much energy is creating such a complex molecule- what
are the advantages mechanically? How do you think these studies can be employed to aid in treatments for
osteoarthritis?
- Christine- comment on how experiments on such molecules can help in understanding synthetic systems.
- End podcast by going around the room and asking what each coauthor thinks is the most exciting aspect of the
paper.
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