Plasma-Assisted Deposition and Pattering of Chitosan/Silk Fibroin Interfaces

Natural polymers are largely proposed as bioactive coatings but their application to surfaces are limited by several factors, such as limited control of the mechanical and chemical stability and weak adhesion to the underlying surface. [1]<br/>Plasma processes provide unique features, such as surface activation, functionalization or assisted polymerization, all of which can be obtained using mild conditions. Plasma modification can enhance the adhesion via covalent bonding between the functional groups formed at the interface between the substrate and the coating. On the other side, commonly adopted cold plasma processes provide limited coating thickness and topography control. In this research, we present a new methodology to obtain spatially controlled deposition of natural biopolymers (silk fibroin and chitosan) using an atmospheric plasma torch fed by an aerosol aqueous solution containing the polymers to be deposited [2].<br/>The resulting coatings were characterized by electron and atomic force microscopy and ATR-FTIR. The stability of the films was tested in phosphate-buffered saline (PBS) solution (pH 7.4) for 2 weeks at 37 °C, followed by treatment in sonication bath for 10 min. Adhesion strength was evaluated by a peeling test.<br/>The presented plasma process provides unique features in a single step, such as surface activation, functionalization and assisted polymerization. Coatings can be obtained using low power (10 W) and at room temperature, resulting in excellent adhesion and stability on a large variety of materials, even with complex shape geometries. Soda-lime glass, a metal alloy (Ti4Al6V), a thermoplastic polymer (polyethylene terephthalate), a silicone rubber (poly-dimethylsiloxane) were demonstrated as substrates without the need for any surface pretreatment. The developed method was also successfully optimized for multi-layer deposition of fibroin-on-chitosan and chitosan-on-fibroin, with the aim of realizing patterned surfaces. The biological response of these patterned surfaces was then tested by protein adsorption and cell culture studies, underlining their capacity to guide cell adhesion and control cell proliferation.<br/>This plasma method demonstrated, allows the achievement of spatially controlled deposition, even on complex-shaped substrates, together with the deposition of different biomaterials under mild conditions. This versatility can therefore represent a powerful method for obtaining instructive biosubstrates with optimized cell interactions, suitable for application in biomedical implants and bioelectronics devices.<br/><br/>ACKNOWLEDGEMENTS:<br/>This project has received funding from the Italian Ministry for Education, University, and Research (MIUR) through the “Department of Excellence” program.<br/><br/>REFERENCES:<br/>[1] Song, Jian et al., Adv. Mater. Interfaces (2020): 2000850.<br/>[2] Arkhangelskiy, Artem et al., Adv. Mater. Interfaces (2021): 2100324.