Abstract
Cell surface adhesion phenomena were studied using in vitro animal cell culture. The Radial Laminar Shear Method (RLSM) was developed and validated in order to reliably and reproducibly measure the strength of cell adhesion to surfaces. The RLSM was found to be a simple and inexpensive technique for quantifying the strength of cell adhesion to surfaces, provided it was operated under a set of defined parameters. The strength of cell adhesion supported by native and modified surfaces was measured. BHK21 anchorage dependent cells were shown to be detached from low adhesive surfaces (eg. native polystyrene) with a force of 0.4Nm-2 and a maximum force of 5.5Nm-2 for high adhesive materials (eg. PrimariaTM polystyrene). Most materials (eg. glass, stainless steel) were found to support an intermediate strength of adhesion of 2 to 5Nm-2. A linear relationship between the strength of cell adhesion and contact angle (wettability) was obtained only when materials were used, cleaned and sterilised reproducibly. Surface modifications were earned out to quantify the changes in the strength of cell adhesion to surfaces. The treatment of hydrophobic surfaces by PluronicRTM F-68 or Bovine Serum Albumin (ESA) completely inhibited cell adhesion. Whilst corona discharging or Diamond-Like Carbon (DLC) coating of hydrophobic materials increased the strength of cell adhesion. The above treatments were found to have an insignificant effect on the cell adhesion supported by hydrophilic surfaces. It was shown that cell adhesion properties can directly affect the cell growth characteristics on unmodified materials (eg. native polystyrene, PrimariTM polystyrene, silicone rubber). A material can then be selected for an appropriate biotechnological or biomedical application based on cell adhesion properties. Cell growth properties on DLC coated or chemically treated materials did not relate to the strength of cell adhesion. On these modified materials, the cell growth and adhesion properties need to be fully evaluated when modifications are carried out. The strength of cell adhesion was quantified on materials when protein and surfactants were either coated on surfaces or supplemented in the cell culture medium. It was demonstrated that the strength of cell adhesion to materials was not significantly affected by the surfactant treatment (PVPC30, PVPVA-S630 and PluronicRTM F-68), however, contact angle measurements showed that surfactant adsorption had taken place. For protein treatment (eg. Fibronectin, BSA) to surfaces, the opposite was found to be true for the above parameters. Contact angle measurements did not detect the additional protein in serum supplemented medium. In fact the greatest increases in cell adhesion were found when materials were treated with fibronectin. Finally, it is concluded that the Radial Laminar Shear Method can be successfully used to quantify the effects of surface modifications on the strength of cell adhesion. This is provided that the test is carried out using the defined parameters.