Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsFN has a pI of 5.3 [288], thus at physiological pH this protein will possess a smallnegative charge. This suggests that electrostatic interactions may govern thisinteraction with the positively charged PEIc and PLLc [289, 290]. However, similarto the adsorption behaviour of CN type I, the measured s∞ on PEIc and PLLc issignificantly smaller than for adsorption to negatively charged PAAc. The s∞determined for FN adsorption to Au, Ti-oxide and Ta-oxide of 14.6, 10.6 and 11.0mg/m 2 [291] are comparable with the FN adsorption measured to PAAc. The pKa ofboth PAA and Ta-oxide are both approximately 3, thus, would both have a similarnegative charge [286, 291]. FN adsorption has also been reported onto othernegatively charged surfaces including anionic phospholipids and silica [292]. TheA biomol measured for FN adsorption to PAAc of 49 nm 2 (Table 5.2) is significantlylower than the size of FN of 384 nm 2 as measured by scanning electron microscopy[288], suggesting that FN adsorbs end on, with only a 12.8% of the protein in contactwith the surface. This allows for the formation of a dense biomolecular layer. Asimilar A biomol for FN adsorption to gold of 45 nm 2 has been previously reported[291]. The A biomol measured for FN adsorption to PEIc of 234 nm 2 (Table 5.2) ismuch closer to the size of FN, and suggests that FN adsorbs side on in this case. TheA biomol measured for FN adsorption to PLLc of 2490 nm 2(Table 5.2) is largecompared to the size of FN and suggests only 15% surface coverage of FN to PLLcis possible under the experimental conditions used here.The counterintuitive adsorption of both CN and FN to PAAc, which shouldelectrostatically repel both CN and FN, suggests the net charge of the protein mustnot be dominating its surface adsorption behaviour in this case. Contributing factorsto FN adsorption may be electrostatic interactions between positively chargeddomains of the protein and negatively charge surface moieties, a specific interaction5-199