Modification of the hydrophilic/hydrophobic characteristic of zein film surfaces by contact with oxygen plasma treated PDMS and oleic acid content

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2015-11, Vol.135, p.433-440
• Main Authors: Gezer, P. Gizem, Brodsky, Serena, Hsiao, Austin, Liu, G. Logan, Kokini, Jozef L.
• Format: Article
• Language: English
• Subjects: Contact angle; Dimethylpolysiloxanes - chemistry; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Microscopy, Atomic Force; Oleic acid; Oleic Acid - chemistry; Oxygen - chemistry; Oxygen plasma; Plasticizers; Plasticizers - chemistry; Roughness; Silicone resins; Surface; Surface Properties; Zein; Zein - chemistry
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2015.07.006

[Display omitted] •Tunable hydrophobic and hydrophillic zein films were obtained with a combination of solvent casting and different oleic acid contents.•Casting zein on oxygen plasma treated PDMS successfully modified zein surfaces.•Increasing oleic acid content made the surface more hydrophilic when cast on oxygen plasma treated PDMS.•Oleic acid was found to play a significant role in self-assembly of zein films.•The nano-scale properties of zein films were characterized by atomic force microscopy. Zein has been widely studied as a biopolymer due to its unique film-forming abilities. Surface properties are of high importance for certain applications which include microfluidics and tissue engineering, as they drastically affect the end result. It is important to develop techniques to modify zein surface properties without compromising bulk material properties. In this study, we developed a facile technique to change the water affinity of zein film surfaces, compatible with patterning techniques via soft lithography. This is achieved by a simple solvent casting technique onto a polydimethylsilohexane (PDMS) substrate that was exposed to oxygen plasma. Water contact angle measurements (WCA) were used to assess the hydrophillicity of zein surfaces and they reached as low as 20°. Atomic force microscopy, optical absorbance and light microscopy were used to study the characteristics of the film and its surface topography. Hydrophilic zein surfaces had higher roughness values compared to hydrophobic ones. Surface roughness, introduced by sandpaper and gratings does not have the same effect as surface chemistry. The amphiphilic nature of plasticizer oleic acid also contributed to the change in the water contact angle of the films. In conclusion, we demonstrated that zein film’s surface properties can be controlled by its ability to self-assemble depending on the substrate that it is being cast on.