Nanoscale conformation and compressibility of cartilage aggrecan using microcontact printing and atomic force microscopy

The aggrecan layer height and compressibility of cartilage aggrecan were investigated which enabled a direct estimate of the stiffness of the layer. It was found that the polymer layer could be sandwiched between surfaces with a much larger radius of curvature by using a colloidal tip having having a radius on the micrometer scale, resulting in a simpler boundary condition for measurement of mechanical moduli. The shear behavior of polymer layers were also studied with brush height obtained simultaneously using lateral force microscopy. The aggrecan height results were found to be nonhysteretic which decreased with increasing IS from 0.001 to 1 M under constant normal compressive load and with increasing normal load at constant IS.