Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsDNA, may contribute to the observed behaviour. To look more closely at theelectrostatic forces occurring at the surface, the solution pH was varied between 4and 9 whilst keeping the salt concentration constant. This should only alter thesurface charge of the ALAPP surface whilst not altering the charge of the DNAmolecule, which is negatively charged over most of the pH range [20]. Interestingly,the DNA was constant over the pH range of 6-8, but increased suddenly when the pHdropped to 5 and decreased slightly when the pH was increased to 9 (Figure 3.6).This corresponds well to the changes in -potential measured for the freshlydeposited ALAPP film. To demonstrate this, the DNA was plotted against -potentialover pH of 5-9, shown as Figure 3.7. A linear relationship is seen over the surfacecharge range. This result strongly suggests that DNA is interacting with the ALAPPelectrostatically, however, this results also implies that the net negative charge of thepolymer surface does, in part, inhibit the adsorption of DNA. The significant amountof DNA adsorption occurring at a -potential of zero (0.2 mg/m 2 ), whereupon DNAadsorption is governed primarily by hydrophobic binding, further suggests theimportant role hydrophobic interactions play for DNA adsorption to ALAPP films.3-119