Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsThe ultimate application of SPR is for probing interactions of biomolecules. Thus,if investigating the adsorption of a 5 nm thick biopolymer layer onto a PLL array ofthickness varied from 0-200 nm a resonance angle shift to higher angles is expectedas shown in Figure 5.6, where the theoretical reflectivity versus angle of incidence isshown both with (dotted) and without (solid) a biopolymer layer. Real-timebiomolecule adsorption experiments are typically achieved using a fixed angleapproach, thus, the change in reflectivity at the optimised angle from Figure 5.5B of49.3° for each polymer spot after the addition of a 5 nm biopolymer layer is shown inFigure 5.7A. An equivalent response of approximately 23 units is measured for spotsover a range of thicknesses of 0 – 5 nm, however, this response decreases rapidly forpolymer spots thicker than 10 nm and almost no change is observed at this fixedangle for the spot with a thickness of 200 nm. This exemplifies the difficulty facedwhen measuring SPR signal changes for inhomogeneous surfaces.5-177