Ortiz Laboratory @ MIT

Mission Statement

Download a PDF Description of the Ortiz Research Program (PDF, DOC)

Biological materials, such as musculoskeletal and exoskeletal tissues, have developed amazingly complex, hierarchical, heterogeneous nanostructures over millions of years of evolution in order to function properly under the mechanical loads they experience in their environment. The Ortiz research group studies these fascinating materials using expertise in the new field of "nanomechanics"; i.e. the measurement and prediction of extremely small forces within and between nanoscale constituents in order to determine the local origins of macroscopic physical phenomena. Novel experimental and theoretical methods are employed (see table below) in order to probe and understand fundamental nanoscale surface, bio-, and polymer physics mechanisms and design principles; i.e. how they work in tandem and what universal laws they follow to achieve a particular function. The objective of the Ortiz research program is to provide a fundamental molecular-level understanding of the mechanical function, quality, and pathology of structural biological materials. A quad-tiered approach is taken to achieve this goal which includes; nanomechanics of single cells and their pericellular matrix, individual molecules, biomimetic model systems, and in-tact tissue-level properties (see One-Page Group Summary Powerpoint PDF). The scientific foundation being formed has relevance to both the medical and engineering fields. Nanotechnological methods applied to the field of musculoskeletal tissues and tissue engineering hold great promise for significant and rapid advancements towards tissue repair and/or replacement, improved treatments, and possibly even a cure for people afflicted with diseases such as osteoarthritis. In addition, the discovery of new nanoscale design principles and energy-dissipating mechanisms will enable the production of improved and increasingly advanced biologically-inspired structural engineering materials that exhibit "mechanical property amplification" - that is, dramatic improvements in mechanical properties (e.g. increases in strength and toughness) for a material relative to its constituents. A summary of some of the biological materials studied and the experimental and theoretical methodologies utilized in the Ortiz research group are given in the Table below.

MATERIALS OF INTEREST

METHODOLOGIES

Cartilage	the biomacromolecular connective tissue found on the surfaces of movable articular joints whose main function is to bear stresses during joint motion
Bone	the calcified connective tissue that makes up the skeleton of most vertebrates
Seashells	nacre : the highly mineralized aragonite-based brick-and-mortar inner layer of gastropod mollusc shells
Armored Fish Scales	the multilayered mineralized structure protecting ancient fish composed of ganoine, isopedine, dentin, and bone
Shell of a Hot Vent gastropod	very strange material - stay tuned!

· spatially specific high-resolution (piconewton) force spectroscopy (HRFS)
· single molecule force spectroscopy (SMFS) and imaging
· chemical force microscopy (CFM)
· lateral force microscopy (LFM)
· atomic force spectroscopy (AFM) imaging
· instrumented and AFM-based nanoindentation
· dynamic nanomechanics; force relaxation, creep, oscillatory loading
· single cell mechanics
· nanoscale theoretical simulations
· finite element analysis

Current research interests :
1) nanomechanics of diseased, aged, and injured tissues
2) the use of nanomechanics methodologies in regenerative medicine; e.g. as an optimization tool for engineered tissues (e.g. genetically manipulated, stem-cell based)
3) correlating cellular function, pericellular matrix synthesis, and single cell biomechanics
4) temporal evolution of the nanomechanical properties of single cells (e.g. stem cells, chondrocytes, etc.) with in vitro culture time and pericellular matrix growth as a function of various environmental factors (e.g. scaffold material, growth factors, etc.)
5) development of experimental and theoretical techniques for the measurement and analysis of nanoscale visco(poro)elasticity of biological materials and single cells
6) heterogeneity, homogenization effects, multilayering, and grading in structural biological materials

·Tai, K.; Pelled, G.; Sheyn, D.; Bershteyn, A.; Han, L.; Kallai, I.; Zilberman, Y.; Ortiz, C.; Gazit, D., "Nanobiomechanics of repair bone regenerated by genetically modified mesenchymal stem cells," Accepted, Tissue Engineering, 2008.
·Ortiz, C.; M. C. Boyce, "Bioinspired structural materials," Science Vol 319 2008, pg 1053-1054. PDF
·Han, et al. "Nanoscale shear deformation mechanisms of opposing cartilage aggrecan macromolecules," Biophysical Journal 2007, 93: L23-25L. PDF
· Tai, et al. "Nanoscale heterogeneity promotes energy dissipation in bone," Nature Materials 2007, 6, (6), 454-462. PDF, Supplementary Information PDF
· Ng, et al. "Nanomechanical Properties of Individual Chondrocytes and Their Developing Growth Factor-Stimulated Pericellular Matrix," Journal of Biomechanics 40, 5, 1011-1023, 2007. PDF