Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsthe surface behaviour of DNA was of most interest at physiological pH. At this pH,the ALAPP and PEG modified surfaces gave -potentials of -28 mV and -20 mVrespectively. As predicted by equation 3.4, a linear relationship was observed withgood correlation (Figure 3.4B and C), suggesting that this model is appropriate overthe concentration range studied.The DNA adsorption characterised in Figure 3.4 was conducted at a pH of 7.4,whereupon the ALAPP film had a measured -potential of approximately -20 mV.As DNA adsorption was able to proceed despite the negative surface charge, thebinding of DNA to ALAPP must depend on more than just electrostatic interactions.By application of the Langmuir model (equation 3.3) to the data sets shown in Figure3.4, s and K for DNA adsorption to ALAPP were found to be 4.96 mg/m 2 and1600 ml/mg respectively, suggesting a high affinity of the ALAPP film for DNA. Forcomparison, at an equivalent pH Elaissari et al., reported a s and K for theadsorption of polyadenylic acid onto latex particles of 1.21 mg/m 2 and 90 ml/mgrespectively [22]. At an optimised pH (4.4), whereupon the latex particles had apositive charge of +60 mV, the reported s and K for the adsorption of polyadenylicacid was 2.62 mg/m 2 and 3630 ml/mg respectively [22]. Although correlation withthe Langmuir model fits well with the data presented, deviation from this model athigher DNA would be expected as a result of the electrostatic repulsion betweenadjacent adsorbed DNA molecules.3-115