Surface physicochemical properties and mechanical stimuli play influential roles in cell proliferation and protein attachment.For example,cell adhesion and growth is critical to the design of biomimetic scaffolds,whereas platelet attachment to vascular grafts and stents is undesirable because it leads to thromboembolism.Plasma-assisted surface modifications resulting in distinctly different biochemical affinities will be discussed,and the capability of tuning the surface chemical properties of biopolymers and,consequently,control cell adhesion will be demonstrated in the light of results showing the dependence of cell spreading and growth on surface chemical functionalization.In addition,changes in the friction characteristics of bovine articular cartilage due to mechanical stimuli will be shown to correlate with variations in the expression levels of proteins secreted from chondrocytes in the superficial layer of cartilage.The important role of these proteins in the formation of a sacrificial boundary layer that effectively lubricates the cartilage surface and prevents osteoarthritis will be discussed in the context of experimental results.These findings suggest the existence of an interfacial mechanism of biological regulation and mechanical function in which physical forces regulate joint lubrication through complex biochemical pathways.