Patterned and switchable surfaces for biomaterial applications

Chapter 4 – Formation of a chemically patterned substrate for cell microarray applicationsand the surface. Furthermore, no difference was observed between PAA and PVPspots with and without NSANB after washing (Figure 4.4C), suggesting the NSANBdid not directly link this polymer to the surface utilising amine functionality on theplasma polymer layer, which should be shielded by the dense PEG coating. Thiscontrasts with PAA functionalised with NSANB, which showed equivalentautofluorescence before washing irrespective of the amount of NSANB present(Figure 4.4B). However, after washing all the PAA spots were removed, judging bythe absence of fluorescence (Figure 4.4D), except for the polymer spot containing thehighest concentration of NSANB of 2.0 mg/ml (Figure 4.4D). This suggests that byintroducing amine functionality to the NSANB prior to incubating with PAA acovalently immobilised PAA array on the PEG coating can be formed. Furthermore,the PEIc and PLLc that were covalently immobilised to the surface could beobserved even after extensive washing (Figure 4.4C). Spots printed from polymersolutions without crosslinker were removed almost completely (the column of spotson the right of each array set) (Figure 4.4C). This confirms that the spots formedfrom the derivatised polymers are covalently cross-linked to the surface and are ableto withstand extensive washing.The polymer spots were further analysed by profilometry before and afterwashing in order to quantitatively observe the removal of unbound polymer. Theheights of spots formed on a PEG coating from polymer concentrations of 2, 1, 0.5,0.25, 0.1 and 0 mg/ml containing 1 mg/ml NSANB were measured. All polymersexhibited an increase in height with increasing polymer solution concentration(Figure 4.5). However, after washing the height of PAA and PVP spots at all initialpolymer concentrations was reduced to near zero (Figure 4.5A and D), whilst theheight of PEIc and PLLc remained statistically indistinguishable after washing from4-144