QCM-D analysis of material–cell interactions targeting a single cell during initial cell attachment

Clarifying material–cell interactions after eliminating various effects including cell–cell interactions is a very important issue in tissue and cell engineering. We investigated several cellular behaviors dynamically after growing cells individually one by one to eliminate cell–cell contact by direct observation using the quartz crystal microbalance with dissipation (QCM-D) and microscopy. The initial cellular behaviors of several cells (adsorption, attachment and spreading of L929 mouse fibroblasts) on the gold electrode of the QCM-D were classified into three regions according to the slope of the Df plots: I, cell adsorption and desorption; II, attachment and spreading; and III, secretion of microexudates. When the number of cells increased which leads to increase of cell–cell distance, region III disappeared and the slope of the Df plots in region II became steeper. The behavior related to the variation in the number of attached cells was indicated by the adhesion strength between the cells and the gold electrode. Furthermore, the slope of the Df plots was not shown on the (poly(2-methacryloyloxyethyl phosphorylcholine)–co–2-(methacryloyloxy)ethylthiol)-modified gold electrode and almost all of the cells were not attached to the polymer surface. The initial cell attachment behavior, especially the strength of cell adhesion to the material surface, was evaluated quantitatively by determining the slope of the Df plots using the QCM-D system.