Cell Adhesion to Borate Glasses by Colloidal Probe Microscopy
Sheldon M. Wiederhorn, Carl G. Simon Jr., Young-Hun Chae
The adhesion of Osteoblast-like cells to silicate and borate glasses was measured using colloidal probe microscopy in a cell growth medium. The probe consisted of silicate and borate glass spheres, 25 µm to 50 µm in diameter, attached to the tip of an atomic force microscope probe. Variables of the study included glass composition and the time of contact of the cell to the glass. Increasing the time of contact from 15 s. to 900 s increased the force of adhesion, which followed a power law function of time with an exponent ranging between 0.3 and 0.5. Of the seven glasses tested, five had exponents close to 0.5, suggesting diffusion as the rate limiting step in the adhesion process. The data supports the assumption that the force of adhesion depended on the formation of a calcium phosphate reaction layer on the glass surface caused by corrosion of the glass and a reaction between Ca+2 ions from the corrosion process with PO4-3 ions in the medium. Those glasses that did not form a calcium phosphate layer on the glass surface exhibited a weaker force of adhesion relative to those glasses that formed a calcium phosphate layer on their surfaces. The experiments described in this paper show that colloidal probe microscopy can be an effective and rapid method of evaluating the first stage of cell adhesion to extracellular materials.