Just a millimeter or so thick, the layers of cartilage in our knees can withstand compressive stresses of hundreds of kilopascals and tensile stresses ten times greater. Cartilage owes its remarkable resilience to the complex behavior and arrangement of its various molecular components. Unfortunately, like many carefully engineered devices, cartilage can go wrong. Twenty-one million Americans endure osteoarthritis, a painful degradation of cartilage in knees and other joints.
Candidate materials for synthetic cartilage are assembled from molecular building blocks. Drugs operate through molecular interactions. Treating cartilage diseases, therefore, depends on understanding the mechanical properties of cartilage at the molecular level. That goal is now one basic research step closer, thanks to a new technique for probing the nanomechanics of cartilage.
Seven years ago, MIT’s Alan Grodzinsky and Mike Buschmann, his graduate student at the time, identified the main source of cartilage’s compressive strength: electrostatic repulsion between glycosaminoglycan (GAG) molecules. 1...
