Analysis of surface coverage in regards to surface functionalization : A microscopic approach

Abstract: The understanding of how white blood cells react when coming into contact with various surfaces is of major importance for a wide range of biomaterials and biosensor applications. In this study it is investigated if it is possible to determine how neutrophils react to a certain type of sensor chip called cell clinic being developed. This study investigates the cell surface coverage on the sensor chip and how it correlates to the signal response of the sensor at hand. Neutrophils, as other white blood cells, are cells that quickly adhere to surfaces and during the adhesion process they activate at different levels depending on i.e. type of surface or surface functionalization, this activation can be visualized by the change in morphology. While measuring the change of capacitance with the cell clinic sensor during cell adhesion, the cell surface coverage is of main importance. The main focus of this diploma work has been to develop an image analysis script capable of conducting automated analysis on a large body of images estimating the surface coverage. Input data for this modeling is taken from fluorescent microscopy images. The experiments conducted during this project have indicated that white blood cells adhered to the sensor surface shows signs of being activated also without external activation. This clearly shows that knowledge of how neutrophils react to surface modifications is of great importance as well as the awareness that any surface may trigger a response from the immune system i.e. neutrophil activation, so also in the cell clinic. It is a fact that it might be difficult to evaluate the effect of a foreign substance on the neutrophils while a significant amount is activated from being in contact with the surface. Regarding different surfaces the white blood cells does not display any preference of adhering to any specific surface. The surfaces used in this project was silicon oxide wafers, silicon oxide wafers with a nitride surface functionalization and the intended sensor chip; however the addition of PMA clearly shows an effect on how many cells that adheres to the surface as well as the average area of each cell.