Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applications% (v/v) ethanol. Images were taken with an unmodified NP-20 tip in contact modewith an initial vertical deflection of -2.7 V.A2.3. ResultsA2.3.1. Polymer spot characterisationFive different polymers were chosen for formation of a polymer array. Thedistinctive feature of three, PALA, PLL and PEI, is their amine functionality, whichallows formation of a covalent bond with the phenylazide cross-linker as well asintroducing an overall positive charge at neutral pH; the isoelectric point of amines istypically >10. This positive charge was selected for the potential electrostaticinteraction with the negative charges on the phosphate backbone of DNA. As acontrol, a negatively charged polymer in PAA was chosen, as well as a neutral andslightly hydrophobic polymer in PVP. The structure of each of these polymers isshown in Figure A1.0. Each of these polymers is also readily solubilised in water,which allows for the simple printing into an array without having to use organicsolvents for printing or cleaning.G