Abstract
This work introduces a novel process for the fabrication of free-standing biodegradable casein devices with micro-and nanoscale regular and biomimetic surface features. Fabrication of intermediate polydimethylsiloxane (PDMS) moulds from photoresist masters and liquid-casting of casein is used to transfer arbitrary geometrical shapes onto the surface of casein devices. Casein film composition was optimized for mechanical stability and pattern resolution. It was found that 15% casein in 0.2% NaOH solution, mixed with 10% glycerol, and cross-linked by addition of 2% glutaraldehyde produced the best pattern transfer results. Biomimetic cell-like shapes were transferred onto casein by use of bioimprinting of two-dimensional cell-cultures into PDMS. To demonstrate this process, C2C12 mouse myoblasts were cultured on microscope slides, replicated into PDMS and casein using liquid casting and drying. Recessed alignment grids were integrated into the microscope glass slides to facilitate direct comparison of original cells and their bioimprints on PDMS and casein. Optical microscopy and atomic force microscopy confirmed the transfer of micron-scale morphological features, such as cell outlines, nuclei and larger lamellipodia, into the casein surface. Nanoscale feature resolution in casein was found to be limited compared to the PDMS intermediate moulds, which was attributed to limited wetting of the aqueous casein solution. Strategies to increase resolution of the casein transfer step, as well as degradation behavior of the fabricated devices in cell culture media are currently underway. Substrates fabricated with this process have applications in stem cell engineering, regenerative medicine, and implantable devices. (C) 2015 American Vacuum Society.