The integrins are transmembrane adhesion molecules and act as cell-adhesion receptors that form contacts with extracellular matrix (ECM). They interact with one of many ECM components often by recognizing the tripeptide arginine-glycine-aspartic acid (RGD) in the substrate (e.g., laminin, fibronectin, or vitronectin).

In the present study, we have measured the interaction forces between living malignant melanoma B16F10 cells and three types of polystyrene latex (PSL) spheres, using the Atomic Force Microscopy (AFM) with the colloid probe method: (i) bare PSL (bare/PSL) spheres; (ii) carboxyl-coated PSL (COOH/PSL) spheres; (iii) RGD-coated PSL (RGD/PSL) spheres, which were modified by RGD-containing proteins, namely ProNectin^® F Plus. The adhesion forces of these PSL spheres with the surface of B16F10 cells give the order of (bare/PSL) < (COOH/PSL) < (RGD/PSL) in magnitude. This strong adhesion of the RGD/PSL sphere to the cell surface is considered to originate from the integrin-RGD binding.

Also, we have measured the cell-particle adhesion forces in a culture medium including RGD tripeptides, which inhibit the adhesive function of the cell integrins by binding with them. The adhesion of COOH/PSL and RGD/PSL spheres became weaker with increasing the concentration of the dosed inhibitors, while that of bare/PSL sphere remained almost constant. These results indicate that the integrins play an important role in cell-particle adhesion, depending on the surface chemistry of particles. The possible mechanism of cell-particle adhesion will be given in our talk.