Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsin the gel was achieved using the Molecular Dynamics FluorImager 595 andImageQuant software 4.1, Molecular Dynamics.2.2.8. DNA adsorption and desorption studiesDNA adsorption and desorption studies were initially conducted in a custom-builtflow cell, as depicted in Figure 2.3, used in conjunction with a Leitz Fluorescencemicroscope. The flow cell consisted of a steel bottom plate that the substrate could beclamped to by placement of a moulded silicone rubber piece, cover slip and anacrylic top plate. A platinum counter electrode was clamped between the siliconerubber mould and the cover slip. The circular silicone rubber piece with a centralsquare cavity was formed by curing Sylgard 184 silicone elastomer kit in a brassmould for 30 min at 280 °C after mixing of the elastomer components and extensivedegassing in vacuum. Polypropylene tubes (diameter = 1 mm) were positioned in themould before curing. The final volume of the flow cell chamber was 100 l.Patterned ALAPP modified PEG grafted samples were clamped into the flow celland 200 l of ultra pure water was injected. After washing, 10 l of 290 ng/l 6-carboxyfluorescein (6-FAM) labelled (ex 497 nm, em 514 nm) 16-meroligonucleotide (5’-FAM-GCCAGAAGCCAGTACT-3’) (Geneworks) solution inultra pure water was injected into the flow chamber and adsorption was observed.Positive voltage (0 – 2 V) was applied to the surface with a platinum wire counterelectrode for typically 2 min to investigate electro-induced DNA adsorption.Likewise, negative voltage (0 – -2 V) was applied to the surface with a platinum wirecounter electrode for typically 2 min to investigate electro-induced DNA desorption.Ultra pure water was injected to remove unbound DNA at various stages and forfinal washing.2-71