Employment of Melt Electrowriting for the design of regenerative grafts

BACKGROUND Cell-sized structures such as electrospun mats have been shown to tailor cell growth in a variety of ways and thus have great potential in the development of regenerative implants. Due to their thinness of several hundreds of micrometers, these mats mostly act as coatings on larger matrices, but the use of cytotoxic solvents complicates the translational process. A relatively new technique, melt electrowriting (MEW), offers similar properties but relinquishes cytotoxic solvents. Instead, thermoplastics such as polycaprolactone (PCL) are melted and processed under high voltage to form fibers with a precise fiber diameter that can be deposited in highly ordered meshes using a three-axis system. Outcome of the MEW processes are fiber architectures with defined fiber diameter, fiber spacing and tailored porosity within the cellular dimensions. This contrasts with previous electrospun mats, which mostly exhibit chaotic fiber architectures. RESEARCH QUESTIONS Due to the novelty of MEW, all studies so far used highly customized laboratory printers to produce MEW membranes, complicating translation to the clinic. Therefore, one of the first commercial MEW printer had to be established and the printing characteristics needed to be found to maintain homogeneous fiber diameters throughout the printing process and to investigate the compatibility with other printing techniques. Large tympanic membrane defects, such as those caused by chronic otitis media and other conditions, are currently closed with autologous materials in an elaborate procedure that may result in side effects such as hearing loss. Customized MEW meshes could improve this situation if they demonstrate similar mechanical and vibrational properties as the TM or the respective autologous materials. To this end, the variety of different design parameters such as fiber diameter, fiber spacing, layer-to-layer orientation, and number of layers should be investigated. Ideally, the collagen fiber structure