Sensing surfaces: Challenges in studying the cell adhesion process and the cell adhesion forces on biomaterials

A major turning point in the biomaterials field would be to develop tools that can offer greater insight into cell behaviour on material surfaces. Obtaining this information is very important for the development of long-term implantable materials because it can aid in improving cell adhesion and proliferation properties. The amalgamation of multiple disciplines has already produced many interesting techniques and approaches for the characterisation of cell adhesion processes and force adhesion strength determination on biomaterials. In this review, the authors provide an overview of the recent techniques developed for the noninvasive in situ study of the adhesion process as well as systems that allow the measurement of adhesion force strengths over biomaterials. Techniques based on light internal reflection, electrochemical impedance spectroscopy, and the quartz crystal microbalance (QCM) are discussed for their capabilities in investigating the cell adhesion process. Conversely, techniques such as flow cells, centrifugation, and cytodetachers are presented for the adhesion force measurement. An emphasis on atomic force microscopy (AFM) will demonstrate its ability to probe both the cell adhesion process and cell adhesion force, depending on the approach used. A discussion is followed on the strengths and/or weaknesses of these techniques. Finally, new trends and possible long-term directions for determining both adhesion process and force are highlighted.