Cells adhesion and their behaviours
When we implant this stent into a patient, the cells will adhere to the biomaterial. And discussing about the adhesion between cells and biomaterials is actually discussing the adhesion between cells and substrates.
Cells adhere to surfaces of biomaterials/ substrates through adhesion proteins using integrins, which is a specific cell receptor to attach to the cell membrane. (Lotfi et al., 2013)
The action has close relations with three kinds of cell junctions, they are Communicating junction (Gap junction-hollow tubes connect cells), Occluding junctions (Tight junction-<5-nm gap, connect adjacent cell membranes) and Anchoring junctions respectively. And there are four types, Desmosome, Hemidesmosome, Adheres junction and Focal adhesion respectively. Basically saying, at Hemidesmosome and Focal adhesion, linking cells to Extracellular matrix (ECM), and both their transmembrane protein are integrin, for other two Desmosome and Adherens junction, which like cells to cells, and the transmembrane protein is cadherin.
Figure2. Major families of cell-adhesion molecules (CAMs) and some other information. (The Cam Family: A new target for monitoring or treating cancers?)
For interactions between cells and biomaterials, which has a close relation with the distance of the gap, when cells live in an extracellular matrix environment, the most area of surfaces of cells connect to strands of ECM material from the substratum by a gap with 50-100 nm, that’s extracellular matrix contacts; and if the gap is in 30-50 nm, is close contact, often surrounds focal adhesions and we can observe the actin filament mesh in cell membrane; but at both focal adhesions in sometimes and hemidesmosomes, the distance of gap is reduced to 10-15nm, and which represents the strongest adhesion, and there is a adhesion protein called vitronectin covers our stent surface and promotes focal adhesion.
They act as an anchor, connecting cells and biomaterials, and for focal contacts, who also transmit signals from the ECM to the cytoskeleton in subsequent behaviours. Figure 3 shows one of possible arrangement of these proteins at a focal contact content. In conclusion, cells pull on our stent via cytoskeleton, and integrins link to cytoskeleton as a force transducer, receive and respond information between them. By the way, surface stiffness is a special factor which can influence at some actions like focal adhesions, cells’ proliferation and differentiation and cytoskeletal organization, all of these actions are proportional to stiffness.
Figure 3. Adhesion proteins involved in focal contacts. (Lotfi et al., 2013)