(531c) Improving Biocompatibility of 3D Printed Stereolithography Resins

The development of low cost, high resolution 3D printing enables the rapid production of custom micro- and millifluidic devices for bioengineering research, including devices with complex, enclosed three-dimensional geometries unobtainable through other techniques. Stereolithography (SLA) printers are of particular interest due to their ability to create smooth surfaces with high resolutions in plastic resins with good optical clarity. However, the adoption of 3D printer technology in bioengineering research is limited by poor biocompatibility of some resins, especially for cell culture applications. Here we describe a resin pre-treatment procedure that resulted in viable cell abundances statistically indistinguishable from no-resin controls for some treatments. Two easily implemented toxicity assays were developed to quantify adverse effects of SLA printed resin: a cell viability assay measuring dose-dependent changes in cell culture viability, and a microbial growth assay using a high-throughput plate reader format to measure changes in cell growth kinetics with exposure to treated and un-treated 3D printed resin. Geometries of the 3D printed resin coupons were varied adjusting the surface area: volume ratio (SA:V) in order to emulate those typical microdevices used in bioengineering research. SA:V was varied up to 7.8 cm^-1 for the cell viability assay, and up to 31 cm^-1 for the microbial growth assay. A device with a 2 cm long channel with a square cross section 1×1 mm has a SA:V of 40 cm^-1. We show resin toxicity can vary with microbial species: a commonly used lab strain of Escherichia coli was far more susceptible to resin exposure than the more robust soil isolate, Pseudomonas putida. The pre-treatment method of UV exposure, leaching in DI H₂O, and thermal treatment was found to remove the adverse effects of 3D printer resin for the strains of bacteria. Resin pre-treatment eliminated up to a 0.5-log reduction in cell viability for P. putida and a 3-log reduction in cell viability for E. coli, compared with no resin exposure. We compare performance of three commonly-used clear resins, Accura 60, Formlabs Clear FLGPCL02, and Somos 9120, with and without pre-treatment. The resin pre-treatment procedure and assays described here can be used to promote wider adoption of 3D printed microdevices in bioengineering research.