Patterned and switchable surfaces for biomaterial applications

Chapter 5 – Surface plasmon resonance imaging of polymer microarraysalbumin (from bovine serum, Sigma), FN (from bovine plasma, Sigma) or CN type I(from rat tail, Sigma) in 1 mM acetic acid was injected at a flow rate of 5 l/s untilSPR signal had plateaued. This slightly higher flow rate was used to ensure kineticmeasurements were not limited by mass transport of the adsorbant from the bulksolution. The 1 mM acetic acid present with CN type I, required for dissolution ofCN type I, reduced the pH from 7.4 to 7.35. The surface was then washed with 0.05M phosphate buffer at 5 l/s to allow desorption of weakly bound biomolecules,before the SPR signal for each spot was measured against the angle of incidence ofthe impinging light beam. The surface was subsequently regenerated by washingwith 0.1% Tween solution at a flow rate of 3 l/s for 60 s and 0.1 M NaOH solutionat a rate of 3 l/s for 60 s or 0.1 M HCl solution at a rate of 3 l/s for 60 s. Thesurface was then washed with 0.05 M phosphate buffer at a flow rate of 3 l/s untilbaseline was again reached. Measurements were taken over an angle of incidencerange of 48-57° while the temperature was held constant at 25 °C.SPR signal intensity versus angle of incidence curves measured for variedpolymer spots before and after biomolecular interaction events were modelled byFresnel equations using Winspall V 3.01 software. Simulation parameters used werea 60° triangular prism using p-polarised light of wavelength 800 nm. Refractiveindex values used were SF10 glass η = 1.71129, gold η = 0.16 + 4.84i [265, 266],biopolymer layer η = 1.45 [248] and water η = 1.32908 [267]. For curve fitting, onlythe position of the resonance angle was considered.5.3.5. Study of switching of PNIPAAm by SPR imagingPNIPAAm spots printed from a 1.5 mg/ml protein solution were selected forstudying temperature switching. 0.05 M phosphate buffer was injected over the5-166