Patterned and switchable surfaces for biomaterial applications

Chapter 5 – Surface plasmon resonance imaging of polymer microarraysA CN type I layer of average thickness of approximately 4 nm was observed todeposit on the PAAc after approximately 2000 s at a bulk concentration of 10 g/ml(Figure 5.14A), however, almost no adsorption was observed on the PEIc and PLLcpolymers (Figure 5.14B-C). This was confirmed by the high k a , K and s∞ of102.4x10 3 s -1 M -1 , 2555.5x10 6 M and 15.7 mg/m 2 respectively and the low k d value of0.401x10 -4 s -1 calculated for CN type I adsorption to PAAc as compared with PEIcwith the next highest k a , K and s∞ of 15.3x10 3 s -1 M -1 , 51.1x10 6 M and 0.5 mg/m 2respectively and the next lowest k d value of 2.999x10 -4 s -1 (Table 5.1). Atphysiological pH CN type I has a weak negative charge, with an isoelectric point (pI)of 5.5 [282, 283], however, positively charged domains along the fibrils, which areimplicated to its structure and biological function [284, 285] can interact stronglywith the negative charge on the PAAc polymer [286] allowing for the end pointattachment of CN type I. The end point attachment of CN type I to PAAc issuggested by the low A biomol of 43 nm 2 measured (Table 5.2) as compared with thesize of CN type I of 450 nm 2 [287], suggesting only 9.6% of an adsorbed CN type Imolecule is in contact with the surface. The measured s∞ of 15.7 mg/m 2 is higherthan the s∞ of 6-7 mg/m 2measured previously for CN type I adsorption ontopoly(ethylene terephthalate) [287]. The end on adsorption regime of CN type I toPAAc proposed would allow for a higher binding capacity.A FN layer was observed on PAAc of average thickness of 1.0 nm afteradsorption for 1500 s at 10 g/ml (Figure 5.15A), and smaller thicknesses of 0.5 nmand 0.2 nm were observed on PEIc and PLLc respectively (Figure 5.15B and C). The s∞ for FN adsorption to PAAc, PEIc and PLLc were found to be 15.3, 3.2 and 0.3mg/m 2 , respectively (Table 5.1).5-198