Patterned and switchable surfaces for biomaterial applications

Chapter 2 – Spatially controlled electro-stimulated DNA adsorption and desorption for biodeviceapplicationsthat are easy to transfect. Furthermore, as potentially thousands of cell colonies canbe produced all with a slightly different phenotype, processing of these cell arrays istime consuming, particularly when differences are subcellular and subtle, making itdifficult to differentiate between transfected cells and the lawn of non-transfectedcells Recently, a platform for a transfection chip using plasma polymerisation-basedmodification of substrate materials was developed [35]. Plasma polymerisation refersto the formation of highly crosslinked polymerised material by use of a monomer inthe plasma state [38] and can be used to effectively modify surfaces with a thin, welladherent polymer layer that, by the choice of the monomer, contains the desiredfunctional groups without altering the substrate’s bulk properties. Plasmapolymerisation has been achieved with monomers containing alcohol, amine andcarbonyl functiona groups to produce plasma polymers with equivalent functionality[177-179]. This is also a solvent free process, which prevents the presence ofpotentially toxic residual solvent molecules, increasing the biocompatibility of thismaterial. Allylamine has previously been used as a monomer to produce an aminerichallylamine plasma polymer (ALAPP) and have used this surface for thesubsequent high-density grafting of poly(ethylene glycol) (PEG) [35]. Excimer laserablation was then used to produce regions of ALAPP, which sustains cell growth,and PEG, which has been shown to resist cell attachment [33]. Yet, the aminefunctionaities of ALAPP, in their protonated state, are of additional use as theyundergo electrostatic interactions with the negatively charged phosphate backbone ofDNA [36, 180]. ALAPP coated surfaces should, therefore, lend themselves to thesurface-retention of DNA. The investigation of spatially controlled DNA adsorptionon this substrate would aid in the development of a highly useful substrate surface2-64