Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsSUMMARYThe interactions of biomolecules and cells at solid-liquid interfaces play a pivotalrole in a range of biomedical applications and have hence been studied in detail. Animproved understanding of these interactions results in the ability to manipulatebiomolecules and concurrently cells spatially and temporally at surfaces with highprecision. Spatial control can be achieved using patterned surface chemistries whilsttemporal control is achieved by switchable surfaces. The combination of these twosurface properties offers unprecedented control over the behaviour of biomoleculesand cells at the solid-liquid interface. This is particularly relevant for cell microarrayapplications, where a range of biological processes must be duly controlled in orderto maximise the efficiency and throughput of these devices. Of particular interest aretransfected cell microarrays (TCMs), which significantly widen the scope ofmicroarray genomic analysis by enabling the high-throughput analysis of genefunction within living cellsInitially, this thesis focuses on the spatially controlled, electro-stimulatedadsorption and desorption of DNA. Surface modification of a silicon chip with anallylamine plasma polymer (ALAPP) layer resulted in a surface that supported DNAadsorption and sustained cell attachment. Subsequent high density grafting ofpoly(ethylene glycol) (PEG) formed a layer resistant to biomolecule adsorption andcell attachment. PEG grafted surfaces also showed significantly reduced attachmentof DNA with an equilibrium binding constant of 23 ml/mg as compared with 1600ml/mg for ALAPP modified surfaces. Moreover, both hydrophobic and electrostaticinteractions were shown to contribute to the binding of DNA to ALAPP. Spatialcontrol over the surface chemistry was achieved using excimer laser ablation of thePEG coating which enabled the production of patterns of re-exposed ALAPP withIV