Cell Growth on Zein Surfaces Self-Assembled on Patterned Templates

Zein is the alcohol soluble protein of corn. Its secondary structure was investigated by circular dichroism and by X-ray scattering measurements. Both studies considered that the spatial-structure model for zein contains nine successive helical segments folded upon each other in an anti-parallel fashion, linked at each end by glutamine-rich turns or loops and stabilized by hydrogen bonds. The glutamine-rich turns are hydrophilic and locate on the top and bottom surfaces while the hydrophobic domains locate on the surfaces parallel to helices (see Figure 1). Zein tends to maintain its structure and only denatures at extreme conditions. This unique structure can explain zein self-assembly properties. In previous work, zein was adsorbed onto gold surfaces modified by monolayers of 1-octanethiol and 11-mercaptoundecanoic acid, which generated –CH3 and –COOH surfaces, respectively. Surface plasmon resonance (SPR) was used to monitor dynamic mass accumulation on each type of surface. Zein adsorbed on both surfaces but accumulated faster and reached higher pile on -COOH than on -CH3 surfaces. It was proposed that zein rested on different sides of its prism-like molecule when adsorbed onto either hydrophobic or hydrophilic surfaces. The topography of zein deposits was examined by atomic force microscopy (AFM). On –COOH surfaces, large aggregates were observed, with grain size of 300 nm and roughness of 14.5 nm. On –CH3 surfaces, zein deposited evenly with roughness down to 4.1 nm.