Patterned and switchable surfaces for biomaterial applications

Chapter 3 – Comparison of the binding mode of plasmid DNA to allylamine plasma polymer and poly(ethyleneglycol) surfacesboth proteins and DNA whereupon it would be useful to have a surface coating thatis able to universally reduce biomolecular adsorption.PEG layers grafted to a surface are highly effective at preventing proteinadsorption when the surface density of the grafted polymer is sufficiently high suchthat a ‘brush’ regime is reached, whereupon adjacent grafted chains repel one anothercausing the chains to extend away from the surface. A relatively dense PEG brushformed has high exclusion properties due to high conformational entropy.Furthermore, as the hydrophilic PEG hydrogen binds extensively to water, proteinadsorption would lead to unfavourable disruption of the hydrogen bonding. Inaddition, the free energy of the polymer-water interface is minimal, decreasing thedriving force of protein adsorption [65]. As cell attachment is regulated almostentirely by proteins, reduced protein adsorption concurrently leads to a decrease incell attachment.Hook et al. (See CHAPTER 2) [34], combined these two surfaces bydemonstrating the spatially controlled adsorption of DNA on an amine rich ALAPPfilm by sequential deposition of an ALAPP film then grafting of PEG by reductiveamination. Subsequent laser ablation produced a patterned surface that was able todirect DNA adsorption to the regions where the underlying plasma polymer was reexposed.The ability to spatially direct DNA adsorption was of interest, however, amore detailed study of the binding mode of DNA on both the ALAPP and PEGsurfaces is of interest. In particular, the complex chemistry of the ALAPP filmpresents considerable challenges for predicting the DNA-ALAPP interactionsoccurring at the solid/liquid interface. An increased understanding of this systemcould further promote advanced biomolecular manipulation, which is useful for thedevelopment of biodevices.3-100