Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsarray of PAAc, PEIc and PLLc was formed on the PEG coated substrate utilisingphotocrosslinking methods previously developed [215](CHAPTER 4).Fuctionalisation of the polymers with NSANB, which includes a photoresponsivephenylazide group, allowed for the surface immobilisation and intra- and intermolecularcrosslinking of the polymer spots upon UV irradiation (Figure 4.3A).Polymers were spotted at concentrations above 0.25 mg/ml to ensure completecoverage. Both PEI and PLL were spotted at 0.5 mg/ml whilst PAA was spotted at2.0 mg/ml. The higher spotting concentration was chosen for PAA as these polymerswere found to produce immeasurably thin layers at 0.5 mg/ml. A typical SPRi imageof the polymer array is shown as Figure 5.13A. For the polymer array used theaverage thicknesses for PAAc, PEIc and PLLc were 2.2, 8.3 and 18.8 nmrespectively, as determined from the reflectivity versus angle of incidence curvesshown as Figure 5.13B and Winspall curve fitting software. These results correspondwell with previously measured spot thicknesses from profilometry of 1.4, 18.3 and21.3 nm for PAA, PEI and PLL respectively (Figure 4.5). Differences between thesemeasurements could arise from differences between the wet and dry state of thepolymers and varied environmental conditions, such as humidity and temperature,during array formation.This polymer array was investigated for the adsorption and desorption of FN, CNtype I and BSA at various solution concentrations.5-189