Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsdeposition time was 5 s. Freshly deposited ALAPP samples were left overnight inhexamethylene diisocyanate (HDI) at room temperature while excluding the presenceof water. Subsequently, samples were washed thrice for 10 mins in acetonitrile(Merck, 99.9% purity). HDI-modified samples were incubated overnight at 45 °C ina solution of hydroxyl-terminated star-PEG (MW 116,000, 24 arms, ShearwaterPolymers, USA) in acetonitrile (3 mg/ml). Subsequently samples were washed inMilliQ water (18.2 M.cm) three times for 1 hr and finally air dried.5.3.2. Polymerisation of poly(N-isopropylacrylamide)Poly(N-isopropylacrylamide) (PNIPAAm) was prepared as previously described[264]. N-isopropylacrylamide (NIPAAm) (97 %, Sigma) was purified byrecrystallisation in distilled n-hexane. Purified NIPAAm monomer was dissolved to aconcentration of 7 % (w/v) in ultrapure MilliQ water (18.2 M.cm) along with 0.1 %(w/v) 4,4'-azobis(4-cyanopentanoic acid) (ACPA, 98%, Fluka). Polymerisation wascarried out at 55 °C under a nitrogen atmosphere for 45 min. Purification ofPNIPAAm was achieved by dialysis (MW cutoff 124,000 Da) in MilliQ water (18.2M.cm) for 3 days followed by freeze drying.5.3.3. Array formationPoly(acrylic acid) (PAA) (Aldrich, MW 90000, η = 1.527), poly(ethylene imine)(PEI) (MW 70000, η = 1.48) and poly-L-lysine (PLL) (Sigma, MW 70000, η = 1.37)were spotted onto either gold coated SPR chips or gold coated SPR chips that werefurther coated with PEG. Arrays for cell growth studies were spotted onto PEGcoated glass slides.5-163