In order to regenerate, knee cartilage, paradoxically, needs to be placed under mechanical stress, as happens whenever we take a step and our knees take our weight.
When stimulated in this way, the cartilage cells develop receptors that are sensitive to the growth factors produced by the organism. It is also at this very moment that they would be most receptive to medication.
Working on this basis, Dominique Pioletti and Harm-Anton Klok from EPF have claimed to create a material takes the form of a hydrogel matrix, liposometype nanoparticles and, finally, a payload - in this case a dye. When subjected to cyclic mechanical loading, the hydrogel matrix heats up. Once subjected to heat, the diameter of the liposomes shrinks significantly.
This frees up space in the matrix, increasing its permeability and facilitating the release of the dye from the matrix.
The researchers then wanted to verify that it was actually the heating process resulting from the repetition of the mechanical loading that caused the dye to be released.
During an initial experiment, the material was subjected to cyclic mechanical loading but the heat produced was evacuated in order to prevent any local temperature increase in the material.