Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsAlthough currently not utilised for TCM applications, the development of an onchipDNA growth method enables high-density, spatially controlled DNA arrays tobe formed that could be advantageous for TCMs provided this DNA could be takenup and successfully expressed by cells (see section 1.2.1).For TCM applications obtaining high DNA surface concentrations is essential forenhancing transfection efficiencies. It is unlikely that DNA deposited at a particularlocation is taken up entirely by the cells seeded upon it, thus, one must ensure anexcess of DNA by producing surface chemistries with the ability to sustain highDNA surface concentrations. However, DNA immobilisation must also be reversibleso that the DNA can be subsequently taken up by cells [34]. Indeed, transfectionefficiency has been shown to vary significantly with varying surface chemistries[29], demonstrating the importance of optimising DNA-surface interactions for TCMapplications. In order to achieve this various surface chemistries and theirinteractions with DNA have been studied.Generally, the adsorption of DNA onto a given surface is based upon two bindinginteractions, attractive electrostatic forces governed by the negative charge of theDNA phosphate groups and oppositely charged functional groups on the substratesurface as well as hydrophobic effects in aqueous medium associated with theinteractions of nucleobases and nonpolar surface-bound moities (see section 1.1.2)[18, 19]. Hydrophobic effects are more significant for ssDNA as compared withdsDNA due to the role of nucleobases, which are imbedded within the core of ahelical dsDNA strand but comparatively exposed within ssDNA.Electrostatic interactions of surfaces with DNA have been the primary focus forenabling high DNA surface concentrations; thus, formation of positively chargedsurfaces is often desirable for DNA adsorption experiments. This is commonly1-51