Surface Plasmon Resonance (SPR) is not commonly used to study cells. There are a few possible explanations for why this is the case. First, SPR may not seem to be the ideal technique for this type of analysis because you can only see < 500nM above the slide and cell size is on the order of double that value. Second, because cells are large, they could clog tubing. Third, it is not possible to fully regenerate between sample injections. This does not mean that cells cannot be studied with SPR or that kinetic data cannot be obtained. To show how the Reichert SPR can be used to study cells, we ran fibrinogen over two types of cells, Human Embryonic Kidney (HEK) and Chinese Hamster Ovary (CHO). While there is nothing we can do about cell size, the open architecture of the Reichert systems has a definite benefit for doing this analysis. Due to the accessible tubing on the Reichert SPR systems, we were able to increase the internal diameter of the tubing diameter to 0.010” when coupling the cells and then easily changed back to 0.005” internal tubing diameter to obtain good kinetics when flowing the analyte over the cells coupled to the slide. In addition, samples were run without regeneration as a continuous series of injections to avoid regeneration problems altogether.
EXAMPLE 1 HEK CELLS BINDING TO FIBRINOGEN
HEK cells are noted to be easy to grow and have been widely used in cell biology research as well as by the biotech industry to produce therapeutic proteins and viruses for gene therapy1.
For our SPR experiments, HEK was captured over a poly-l-histidine surface and then binding to fibrinogen was studied. Data was fit a to a 2-site binding model in Clamp.
EXAMPLE 2 CHO CELLS BINDING TO FIBRINOGEN
Recombinant therapeutic proteins were introduced over 20 years ago and now generate billions in revenue from a variety of products, including monoclonal antibodies, hormones, etc. For these biopharmaceuticals, CHO-derived cell lines are the preferred host systems because of their advantages in producing complex therapeutics and manufacturing adaptability.2
For our SPR experiments, CHO cells were captured over poly-l-lysine and binding to fibrinogen was studied. Binding was carried out without regeneration between each analyte injection. Data was fit to a Mass Transport Limited 1:1 binding model in Clamp.
2 Xun Xu, et. Al., The genomic sequence of the Chinese hamster ovary (CHO)-K1 cell line, Nature Biotechnology, 2011, Volume 29 (8), pp. 735-741.