Slicing parameter optimization for 3D printing of biodegradable drug-eluting tracheal stents.

In 3D printing, the schematic representation of an object must be converted into machine commands. This process is called slicing. Depending on the slicing parameters, products with different properties are obtained. In this work, biodegradable drug-eluting tracheal stents consisting of a medical grade poly(lactic-co-glycolic acid) and a drug were printed by fused deposition modeling. A slicing parameter optimization method was proposed with the aim of obtaining a particularly low stent porosity and high mechanical strength while maintaining the stent dimensions, which is essential regarding patient-tailored implants. Depending on the three slicing parameters printing pattern, lateral strand distance and spatial fill, porosities of approximately 2-5% were obtained. The tensile strength was used as a measure for the mechanical strength of the implants and was found to be dependent on the porosity as well as the strand orientation relative to the load direction. Strand orientations in load direction yielded the highest tensile strengths of 40-46 MPa and the bonding between individual layers yielded the lowest tensile strengths of 20-24 MPa. In vitro dissolution tests of successfully printed stents were used to predict sustained release of the drug over several months.

Characterisation of fused deposition modeling 3D printers for pharmaceutical and medical applications.

Fused deposition modeling (FDM) is a promising 3D printing technique for the fabrication of personalized drug dosage forms and patient-specific implants. However, there are no market products produced by FDM available at this time. One of the reasons is the lack of a consistent and harmonized approval procedure. In this study, three FDM printers have been characterised with respect to printing parameters relevant for pharmaceutical and medical applications, namely the positioning, hot-end temperature, material residence time, printing velocity and volumetric material flow. The printers are the Ultimaker 2 (UM2), the PRotos v3 (PR3) as well as an in-house developed printer (IDP). The positioning results showed discrepancies between the printers, which are mainly based on different types of drive systems. Due to comparable utilised hot-ends and nozzle geometries, the results for the temperature and residence time distribution measurements were quite similar. The IDP has a high positioning accuracy but is limited with respect to printing velocity, while the achievable material volume flows were different for all printers. The presented characterisation method aims to contribute to the development of a harmonized equipment qualification framework for FDM printers, which could lead to an acceleration and facilitation of an approval procedure for 3D printed products.