Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsPNIPAAm array at 3 l/s and then reduced to 1 l/s whereupon the system was setupto recirculate the buffer. The temperature was then altered between 25 °C and 40 °Cin order to observe the swelling and collapse of the PNIPAAm hydrogel spots.5.3.6. Cell growthA SK-N-SH neuroblastoma cell line was used for cell attachment experiments.Cells were cultured in Dulbecco’s modified eagle media (DMEM) containingpenicillin and streptomycin and incubated at 37 °C, 5% CO 2 and 60-70% humidity.For attachment studies of cells, SK-N-SH cells were seeded onto surfaces at aseeding density of 5x10 4 cells/cm 2 and allowed to attach to the surface after whichthey were incubated at 37 °C, 5% CO 2 and 60-70% humidity for 24 hr. Cells werethen stained with Hoechst 33342 dye (10 mg/mL) for a further 5 min before analysisby fluorescence microscopy. Cells were visualised with an IX81 Olympusfluorescence microscope and analysed using analySIS LS Research v2.5 softwareusing a 360-370 nm excitation filter and a 420 nm suppression filter to detectHoechst 33342 fluorescence. Captured images were modified using AdobePhotoshop software.5.3.7. Kinetic analysisAssuming a one-step kinetic process whereupon the protein in bulk solution (P)adsorbs to a surface binding site (B) to form a surface bound complex (PB), the rateof adsorption of a given protein is given by equation 5.3, where k a is the associationconstant, k d is the dissociation constant, [P] is the concentration of free protein insolution, [B] is the number of free binding sites at the surface and [PB] is theconcentration of surface bound protein [247].5-167