Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsSeveral strategies have demonstrated the ability to reduce protein adsorption,including the surface immobilisation of carbohydrates. However, by far the mostcommonly used and most effective strategy for the formation of non-fouling surfacesavailable today is the surface grafting of PEG [66]. A number of surfacemodification methods designed to reduce non-specific protein adsorption based onPEG coatings have been discussed previously [66].1.4.4.3. DNA uptakeThe third step in the fabrication of a TCM is the uptake of DNA by cells from thesurface. This step includes three primary processes, release of DNA from the surface,diffusion of DNA to the cell surface and transportation of DNA across the cellularmembrane and, typically, into the nucleus. Low transfection efficiencies are likelydue to a failure in one of these processes.As previously discussed, DNA adsorbs to surfaces by hydrophobic or electrostaticinteractions (see section 1.1.2). Therefore, releasing the DNA from the surface isachieved by reversing these interactions. Switching the hydrophobicity at a surfacecan be achieved using hydrogels that respond to temperature changes at their lowercritical solution temperature by altering between hydrophobic and hydrophilic states.This system is readily used for producing switchable cell attachment [64, 73], but hasnot been demonstrated for DNA interactions. Hydrophobicity can also be altered bysolvent changes, however, this is unsuitable for cell cultures. The easiest means ofeffecting DNA release from a surface is by changing the surface charge, typicallyachieved by application of a voltage. Temporal control of DNA adsorption anddesorption has been extensively studied by electrochemical techniques [18, 106,108].1-55