Mammalian cell-adhesion kinetics measured by suspension depletion

Mammalian cell-adhesion kinetics is measured by counting the number of cells lost from suspension due to adhesion to planar or particulate substrata as a function of time rather than by the counting of adherent cells that is widely applied in the literature. A simple statistical model shows that this "suspension-depletion" method is most accurate at low cell counts in the critical early stage of cell adhesion that is diagnostic of forces in close proximity between cell and substratum responsible for cell adhesion. Furthermore, suspension depletion avoids experimental artifacts associated with substratum rinsing and the removal of cells from the substratum using enzymatic and/or mechanical methods. Experimental method is demonstrated for three different cell types (MDCK, epithelioid; MC3T3-E1, pre-osteoblast; MDA-MB-231, human breast tumor) adhering to seven different substrata incrementally sampling the observable water-wettability range in Petri-dish format, as well as MDCK adhesion to particulate carriers in stirred suspension. Suspension depletion is ideal for biocompatibility and fouling studies where quantification of "low-and-slow" cell adhesion is important. In particular, it is shown that a typical method of counting adherent cells does not correctly measure adhesion kinetics to hydrophobic surfaces that are generally resistant to mammalian cell adhesion.