ENGINEERING ZEIN FILMS WITH CONTROLLED HYDROPHILICITY THROUGH ALTERNATIVE SOLVENTS AND UV/OZONE TREATMENT

1. Recently, zein protein attracts much attention, because its unique ability to form hydrophobic matrix could help a delivery system to resist water uptake and maintain the network structure. However, researches indicated that methods need to be developed to modify the surface properties of zein-base products, which essentially affects the loading/encapsulation efficiency and release profile of active compounds 2,3 . This study tried to modify the surface properties of zein films by using alternative solvents, i.e., acetic acid and aqueous ethanol, as well as through the UV/Ozone treatment. The surface morphology and hydrophilicity of resulting zein films were analyzed by tapping mode atomic force microscopy (AFM) and static contact angle analysis respectively. The possible mechanisms of surface modification were accessed by total reflectance fourier transform infrared spectroscopy (ATRFTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis. Experimental Materials Zein, Lot# F40006031C1 (F-4000, regular grade), was obtained from Freeman Industries, LLC (Tuckahoe, NY). Acetic acid (ACS reagent grade, > 99.7%) was purchased from Sigma-Aldrich, Inc (St. Louis, MO). Ethanol (95%) was purchased from Fisher Scientific, Inc (Pittsburgh, PA). Preparation of zein films 0.5% (w/v) zein solutions in 60% ~ 95% (v/v) ethanol (EtOH)/water mixtures or 60% ~ 100% (v/v) acetic acid (AcOH)/water mixtures were used to prepare zein films for the experiments to compare the effects of solvent on the surface properties of zein films. 4% (w/v) zein solution in glacial AcOH was used to prepare zein films for the UV/Ozone treatment. 50µl of each filtered solution was spin-coated onto silicon (Si) wafer using a Laurell WS-400A-6NPP/LITE spin processor (Laurell Technologies Corp., North Wales, PA). Clear and homogenous zein films were obtained and dried in the vacuum oven at 50°C overnight to remove solvent residues and then stored in desiccators under room temperature before analysis.