Controlling cell adhesion using pH-modified polyelectrolyte multilayer films

Adhesion and spreading are key regulators of cell fate regarding survival, growth, function, and differentiation. Modification of medical implant surfaces by a variety of methods is used to control adhesion of tissue cells and, thus, healing of implants. Among methods of surface modification, the layer-by-layer technique is an effective and simple method to tailor surface properties and biocompatibility of biomedical materials. They can be tuned by adjustment of environmental conditions like pH, ionic strength, and temperature during multilayer formation. The focus of the present work is on the effect of pH value of polyelectrolyte solutions on layer growth and surface properties such as wettability, charge, and topography of two similar multilayer systems and the effect on adhesion and growth of mammalian cells. In both multilayer systems, heparin (HEP) is used as strong polyanion while either the biopolymer chitosan (CHI) or the synthetic polymer poly(ethylene imine) (PEI) is used as polycation. The pH value is adjusted to either acidic (pH 5.0) or alkaline (pH 9.0) values, which results in distinct film growth characteristics and surface properties of each system. In addition, the film surface composition clearly affects adhesion and growth of MG-63 osteosarcoma cells (HEP/CHI) and primary fibroblasts (PEI/HEP) due to the dominating molecule in the terminal layer.