Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationswith application for biodevices in general and transfected cell microarrays inparticular.The effectiveness of transfected cell microarrays is hampered somewhat by thelow transfection efficiencies previously documented when DNA undergoesendocytosis if adsorbed to a surface [35, 159], henceforth termed ‘solid phasetransfection’. The reasons for diminished solid phase transfection efficiency incomparison to transfection with vectors dispersed in an aqueous phase are not wellunderstood. It is plausible that the ‘stickiness’ of DNA on the surface impedes orslows down cellular internalisation. Transfection efficiency could be enhanced byinitiating the controlled release of DNA from a suitable substrate surface once a celllawn has formed. The use of a voltage bias as the stimulus for controlled adsorptionand desorption of DNA has been extensively studied on metal electrodes [105, 106].In the present chapter, the production and characterisation of a chemicallypatterned surface that allows spatially controlled cell attachment and DNAadsorption was performed. The method is depicted in Figure 2.1. Here, highly dopedp ++ (low resistivity) silicon wafers have been used as a substrate material. Aftercleaning of the silicon wafer and ALAPP deposition, an aldehyde terminated PEGpolymer was grafted onto the ALAPP layer using reductive amination [181].Subsequent use of masked excimer laser ablation produced the desired patternedsurface. This platform has also been investigated for TCM applications. Once thechemically patterned surface was formed, DNA was spotted onto the ALAPPregions, where protonated amine groups assisted in the adsorption of DNA,preventing desorption of the DNA into solution. Cells were then seeded onto thissurface and only attached on the ALAPP regions. Finally, the cells were analysed forevidence of successful transfection.2-65