Patterned and switchable surfaces for biomaterial applications

Chapter 3 – Comparison of the binding mode of plasmid DNA to allylamine plasma polymer and poly(ethyleneglycol) surfacesHowever, at a higher DNA solution concentration of 500 ng/ml, there seems to bea disparity arising between the two methods of analysis. Notably, the initial sharpincrease in DNA adsorption did not plateau until 15000 s, which is at least 5 timeslonger than measurements taken with QCM. The reason for this disparity may be dueto diffusion limitations in the fluorescence study, that is, the DNA that adsorbs to thesurface is taken from the solution near the surface, forming a DNA depleted layerclose to the surface that DNA from the bulk must diffuse into. A time delay wouldhence be expected between the change of DNA concentration in a near-surface layerand the translation of this change to a concentration change in the bulk, which wasmeasured by the depletion method. Thus, although the measurements of the depletionof solution fluorescence was accurate for thermodynamic studies of DNA adsorption,this disparity suggests that at higher DNA concentration (>200 ng/ml) it is notaccurate for kinetic analysis.3.3.3. DNA adsorption.Langmuir adsorption is widely used for the modelling of biological adsorptionprocesses. In order to minimise the electrostatic repulsion between adsorbed DNAand DNA in solution that is approaching the surface, which would cause a deviationfrom the Langmuir model, lower concentrations of DNA (