Patterned and switchable surfaces for biomaterial applications

Chapter 3 – Comparison of the binding mode of plasmid DNA to allylamine plasma polymer and poly(ethyleneglycol) surfacesresulting in a film thickness of approximately 30 nm as determined by atomic forcemicroscopy (data not shown). After deposition samples were exposed briefly to airbefore storage under a N 2 atmosphere.PEG monoaldehyde (Shearwater Polymers, Huntsville AL, USA) with amolecular weight of 5000 was grafted onto freshly deposited ALAPP films byreductive amination. Grafting was performed under ‘cloud point’ conditions in 20 mlof a 0.1 M sodium phosphate buffer containing K 2 SO 4 (2.2 mg), NaCNBH 3 (60 mg)and PEG (50 mg) at pH 6.2. Freshly deposited ALAPP films were incubated in thePEG grafting solution at 60 °C for 16 hr.3.2.2. Substrate characterisationContact angle measurements were performed by injecting 100 l of 0.2 mfiltered MilliQ water (18.2 M.cm) onto the surface of interest. Advancing contactangles were measured. Three measurements were taken for each sample. Imageswere taken using a Panasonic CCTV camera (WV-BP550) and processed usingImageJ software.X-ray photoelectron spectroscopy (XPS) was conducted on an AXIS HSispectrometer (Kratos Analytical Ltd.) equipped with a monochromatised Al K source. The pressure during analysis was typically 5x10 -8mbar. The elementalcomposition of surfaces was determined from survey spectra, collected at a passenergy of 320 eV. High-resolution spectra were obtained at a pass energy of 40 eV.Binding energies were referenced to the aliphatic hydrocarbon peak at 285.0 eV.Peak fitting of high-resolution spectra was conducted with Vision 1.5 software,Kratos Analytical Ltd. Two areas of each surface were analysed, and each samplepreparation was prepared and analysed in duplicate.3-102