Impact of Post-processing on Biocompatiblity of 3D-Printed Parts made of Formlabs Durable Resin

Abstract

With the increased availability and the improved resolution of 3D printers, fabricating medical devices with 3D printers could enable physicians to tailor device features and dimensions to fit each patient’s needs. Some polymers used in 3D printing, e.g. polylactic acid, are considered biocompatible by the FDA; for photo-reactive polymers, used in SLA printers, the chemical composition, the UV-cure settings, and the post-processing steps, can impact their biocompatibility. The focus of this study was the effects of the post-processing on biocompatibility. In particular, we evaluated how IPA wash time affected the biocompatibility of Formlabs Durable resin. Samples were washed for 1, 3, or 6 hrs in >95% IPA, UV cured at 40C for 10 min, and sterilized via 30/30 gravity cycle. They were then placed in cell media according to ** for 72 hours at 37C with 5% CO2. After 72 hrs the media was then placed on mouse fibroblasts growing in 96-well plates and 12-well plates. Cell growth and cytotoxicity were tracked via ATP levels and membrane permeability out to 72 hrs in the 96-well plates. Morphological changes were observed via light microscopy in the 12-well plates at 6 - 12 hr intervals. Plastic or self-expanding metal stents (SEMs) are inserted in the extrahepatic bile ducts (EHBD) to alleviate cholestasis. With the increased availability and the improved resolution of 3D printers, fabricating biliary stents with 3D printers could enable physicians to tailor stent features and dimensions to fit each patient’s needs. 3D-printed, polymeric biliary stents. The focus of this study was to generate an accurate simulation to predict stent behavior under physiologica One of the many secondary uses of biliary stents is the functionalizing of the stent to disperse drugs into a patient’s system as a postoperative treatment. However, certain resins have different cytotoxicity levels. Durable resin has the desired mechanical properties required for use in biliary stents and is expected to have low cytotoxicity. For this 96-well plate study, we explored the cytotoxicity of durable resin and its effect on cell viability. We achieved this by performing cytotoxicity and cell viability assays simultaneously. Cell membranes degrade as a result of cell death. For the cytotoxicity assay, we used the CellTox Green Cytotoxicity Assay to examine membrane integrity, and this is achieved by a nontoxic cyanine dye that binds to dead cells’ DNA. Live cells will not produce a fluorescent signal because the dye is not membrane permeable. A fluorescent signal is produced when the dye binds to the DNA, and the fluorescence reading is directly proportional to the number of dead cells with a well. The cell viability assay that we used was the RealTimeGlo MT Cell Viability Assay. Viability was measured by the production of ATP within the cells through use of a cell membrane permeable NanoLuc® enzyme which attaches to the ATP. Once attached, the NanoLuc® Enzyme produces a luminescent signal, and the signal correlates with the number of viable cells within a well. After conducting these assays, we concluded that the durable resin was not cytotoxic, however the cells did not produce the expected amount of ATP. Therefore, the durable resin does have an effect on cell viability, but the nature of this effect cannot be deduced without further testing.