Patterned and switchable surfaces for biomaterial applications

Chapter 1 - Introductioncomplex genomic questions proceeds, advanced surface chemistries for microarraysare required.For example, one of the limitations with contact and non-contact printing is thatalthough patterned arrays of DNA, proteins and other molecules are easy to form,there are very limited procedures to prevent cross-contamination or surface migrationof arrayed species. One such strategy was developed by Yamauchi et al., [100], whospatially confined droplets of DNA solution at the surface by using a patterned SAMwith regions of varied hydrophilicity produced using alkanethiols with different endgroups.Spots containing amine, hydroxyl and carboxylic acid groups separated bymethyl terminated alkanethiols were shown to readily confine DNA containing waterdroplets. Baghdoyan et al., [101] sought to confine DNA by adding gelatin to theDNA mixture spotted onto a glass slide in the form of a microarray. This microarraywas subsequently used for reverse transfection with the highest transfectionefficiency occuring at 0.25-0.5% gelatin concentration. Addition of the gelatin washoped to increase spatial control of DNA, however, this was not clearlydemonstrated.Spotted material can also be held in place by introducing various attractiveinteractions between the surface and the spotted material. For example, DNA istypically immobilised to a surface by either covalent interactions, such asimmobilisation of thiolated ssDNA to gold surfaces, or non-covalent interactionssuch as adsorption of DNA to amine functionalised surfaces where electrostaticinteractions dominate or interactions of biotin labelled ssDNA with avidinpresentingsurfaces.1-30