Time-Dependent Metabolic Activity and Adhesion of Human Osteoblast-Like Cells on Sensor Chips with a Plasma Polymer Nanolayer

Abstract

To improve orthopedic implant ingrowth, knowledge of the effect of chemical surface modifications on vital cell function in vitro is of importance. Early in our investigations we recognized that amino groups, positively charged via plasma polymerized allylamine, increased cell growth and the actin-filament formation in the initial cell-material contact phase. To gain insight into continuous vital cell behavior on this plasma polymer layer, here we present the metabolic activity of osteoblasts and their time-dependent adhesion using the sensor chip technology. We demonstrate a new method for continuous 24 hour-measurements with vital human osteoblast-like cells (MG-63, ATCC) on sensor chips (Bionas® SC 1000) modified with plasma polymerized allylamine (PPAAm). The PPAAm film deposited on the chip is a cross-linked, strongly fixed plasma polymer with relatively high amino functionality and well defined chemical surface composition. We assessed continuous cell adhesion and the metabolic activity, i.e., oxygen consumption and acidification. We determined that adhesion of vital cells on PPAAm is not only enhanced shortly (1 h) after cell seeding but remained continuously higher for 24 h, which is significant. This nanometer-thin PPAAm layer did not change the overall metabolic activity of MG-63 cells during 24 h. This tool--using adhesion and metabolic sensor chips--appears to be a suitable method for the recognition of vital cell physiology in biocompatibility measurements of plasma chemical treated surfaces.