Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applications3.4. ConclusionPlasmid DNA adsorption has been characterised on ALAPP and PEG coatingsusing contact angle measurements, XPS, -potential measurements, QCM andfluorescence measurements. These results provide new insights into the nature ofDNA-surface interactions on the surfaces studied, suggesting that ALAPP coatingsdisplay electrostatic as well as hydrophobic functionalities that both contribute toDNA adsorption, allowing for the adsorption of DNA to ALAPP at a pH where thesurface is negatively charged. Furthermore, under the conditions used the s and Kfor DNA adsorption to ALAPP were found to be 4.96 mg/m 2and 1600 ml/mgrespectively, suggesting a high DNA binding capacity. Time course studies of DNAadsorption showed that adsorption to both PEG and ALAPP surfaces followedsimple Langmuir behaviour across the DNA concentration range studied, withALAPP proving to be a superior DNA immobilisation matrix and PEG having alower affinity for DNA. These results suggest that ALAPP coatings are suitable assubstrate surfaces for applications where DNA immobilisation is desired, whilst PEGsurfaces effectively reduce adsorption of double-stranded DNA. Given thesefindings, there is scope to produce two-dimensionally controlled DNA adsorptionpatterns on spatially controlled regions displaying ALAPP and PEG chemistries.Furthermore this chapter demonstrates that the adsorption and desorption of DNA toALAPP surfaces can be stimulated by a positive or negative voltage, respectively. Incomparison, identical voltages applied to a PEG surface did not have an effect on theamount of DNA adsorbed.3-127